HAL 0.5.11 Specification

This document concerns the specification of HAL which is a piece of software that provides a view of the various hardware attached to a system. In addition to this, HAL keeps detailed metadata for each piece of hardware and provide hooks such that system- and desktop-level software can react to changes in the hardware configuration in order to maintain system policy.

HAL represents a piece of hardware as a device object. A device object is identified by a unique identifer and carries a set of key/value paris referred to as device properties. Some properties are derived from the actual hardware, some are merged from device information files and some are related to the actual device configuration. This document specifies the set of device properties and gives them well-defined meaning. This enable system and desktop level components to distinguish between the different device objects and discover and configure devices based on these properties.

HAL provides an easy-to-use API through D-Bus which is an IPC framework that, among other things, provides a system-wide message-bus that allows applications to talk to one another. Specifically, D-Bus provides asynchronous notification such that HAL can notify other peers on the message-bus when devices are added and removed as well as when properties on a device are changing.

The most important goal of HAL is to provide plug-and-play facilities for UNIX-like desktops with focus on providing a rich and extensible description of device characteristics and features. HAL has no other major dependencies apart from D-Bus which, given sufficient infrastructure, allows it to be implemented on many UNIX-like systems. The major focus, initially, is systems running the Linux 2.6 series kernels.

Acknowledgements

Havoc Pennington's article ''Making Hardware Just Work'' motivated this work. The specification and software would not exist without all the useful ideas, suggestions, comments and patches from the Free Desktop and HAL mailing lists.

All trademarks mentioned belong to their respective owners.

Architecture of HAL

The HAL consists of a number of components as outlined in the diagram below. Note that this diagram is high-level and doesn't capture all implementation details.

Details on each component

HAL daemon
A system-wide service that maintains a database of device objects. The daemon is responsible for merging information from device information files and managing the life cycle of device objects. The service is implemented as a daemon and uses helpers to query devices for specific information.
Applications
These are applications consuming services from HAL; this includes desktop-wide session daemons for maintaining policy such as power and disk/volume management.
Callouts
Callouts are programs that run when device objects are added and removed in the HAL daemon. This is useful for 3rd party software to merge additional information onto the device object before it is announced on D-Bus. Callouts are specified on a per-device basis with the info.callouts.add and info.callouts.remove. See the section called “ info namespace ” for details.
Methods
It is possible to specify that a given HAL device object implements a specific D-Bus interface, e.g. org.freedesktop.Hal.Device.Frob with a set of methods Foo, Bar and Baz and have programs run when applications call into this interface. This is defined in the info.interfaces property, consult the section called “ info namespace ” for details.
Addons
An addon can be characterized as a daemon whose life cycle is tied to a device object in HAL. And addon can also claim a specific interface on the device object to provide services to applications for configuring / using the device without having to spawn a new program for every method call. HAL provides a facility to launch/destroy one or more addons per device object using the info.addons property. See the section called “ info namespace ” for details.
Device Information Files
A set of files that matches properties on device objects and merges additional information. These files are used, for among other things, to specify what callouts, methods and addons to associate with a device object. For example, for drives using removable media, HAL includes an add-on daemon which sole purpose is to continously poll the drive to detect media change.

The D-Bus system message bus is used to provide a ''network API'' to applications. As D-Bus is designed to be language independent, potentially many languages / runtime systems will be able to easily access the services offered by HAL.

Device Objects

It is important to precisely define the term HAL device object. It's actually a bit blurry to define in general, it includes what most UNIX-like systems consider first class objects when it comes to hardware. In particular, a device object should represent the smallest unit of addressable hardware. This means there can be a one-to-many relationship between a physical device and the device objects exported by HAL. Specifically, a multi-function printer, which appear to users as a single device may show up as several device objects; e.g. one HAL device object for each of the printing, scanning, fax and storage interfaces. Conversely, some devices may be implemented such that the HAL device object represent several functional interfaces. HAL is not concerned with this duality of either one-to-many or many-to-one relationships between device objects and the actual iron constituting what users normally understand as a single piece of hardware; a device object represents the smallest addressable unit.

Device objects in HAL are organised on a by-connection basis, e.g. for a given device object X it is possible to find the device object Y where X is attached to Y. This gives structure to the device database of HAL; it is possible to map the devices out in a tree. Further, software emulation devices exported by the operating system kernel, such as SCSI emulation for USB Storage Devices, are also considered device objects in HAL. This implies that operating system kernel specific bits leak into the device object database. However applications using HAL will not notice this, such device objects are not referenced anywhere in the device objects that users are interested in; they are merely used as glue to build the device tree.

In addition to provide information about what kind of hardware a device object represents (such as a PCI or USB device) and how to address it, HAL merges information about the functional interfaces the operating system kernel provides in order to use the device; in most cases this is represented on the device object as a string property with the name of the special device file in /dev. In addition to the special device file, a number of other useful properties are merged. This means that both hardware and functional properties are on the same device object, which may prove to be useful for an application programmer. For example, an application might query HAL for the device object that exports the special device file /dev/input/mouse2 and learn that this is provide by an USB mouse from a certain manufacturer by checking the properties that export the USB vendor and product identifiers. See the section called “Device Capabilities” and Chapter 5, Device Properties for details.

Finally, HAL provides one or more D-Bus interfaces for applications to configure and/or use the device. These interfaces are discussed in Chapter 6, D-Bus interfaces.

Summarizing, a device object is comprised by

UDI
This is the the Unique Device Identifer, that is unique for a device object - that is, no other device object can have the same UDI at the same time. The UDI is computed using bus-specific information and is meant to be unique across device insertions and independent of the physical port or slot the device may be plugged into.
Properties
Each device object got a set of properties which are key/value pairs. The key is an ASCII string while the value can be one of several types, see below. Properties are arranged into name spaces using ''.'' as a separator.
- string - UTF8 string
- strlist - ordered list with UTF8 strings
- int - 32-bit signed integer
- uint64 - 64-bit unsigned integer
- bool - truth value
- double - IEEE754 double precision floating point number
Interfaces
Applications can configure and/or use a device using D-Bus interfaces. Typically, there's a one-to-one relationship between capabilities/namespaces and interfaces.

Properties of a device object carry all the important information about a device object. For organisational reasons properties are also namespaced using ''.'' as a separator.

It can be useful to classify properties into four groups

Metadata - Information about how the devices are connected with respect to each other (parent/child relationships), what kind of device it is, what functionality it provides etc.
Facts - vendor ID, product ID, disk serial numbers, number of buttons on a mouse, formats accepted by a mp3 player and so on.
Usage specific information - Network link status, special device file name, filesystem mount location etc.
Policy - How the device is to be used be users; usually defined by the system administrator.

The first category is determined by HAL, the second category includes information merged from either querying the hardware itself or from device information files. The third category is intercepted by monitoring the hardware and finally the last is merged from files under control of the system administrator. This document is concerned with precisely defining several properties; see Chapter 5, Device Properties and onwards for more information. As a complement to device properties, HAL also provides conditions on HAL device objects. Conditions are used to relay events that are happening on devices which are not easily expressed in properties. This includes events such as ''processor is overheating'' or ''block device unmounted''.

There is a special hal device object referred to as the ''root computer device object''. This device object represent the entire system as a whole and all other devices are either directly or indirectly childs of this device object. It has the UDI /org/freedesktop/Hal/devices/computer.

The fundamental idea about HAL is that all ''interesting'' information about hardware that a desktop application needs, can be obtained by querying HAL. Below is a screenshot of a simple device manager application shipped with HAL called hal-device-manager. This application is communicating with the HAL daemon and displays the tree of device objects. The shown properties are for a device object representing a harddisk.

Device Capabilities

Mainstream hardware isn't very good at reporting what it really is, it only reports, at best, how to interact with it. This is a problem; many devices, such as MP3 players or digital still cameras, appear to the operating system as plain USB Mass Storage devices when the device in fact is a lot more than just that. The core of the problem is that without external metadata, the operating system and desktop environment will present it to the user as just e.g. a mass storage device.

As HAL is concerned with merging of external metadata, through e.g. device information files, there needs to be some scheme on how to record what the device actually is. This is achieved by two textual properties, info.category and info.capabilities. The former describes what the device is (as a single alphanumeric keyword) and the latter describes what the device does (as a number of alphanumeric keywords separated by whitespace). The keywords available for use is defined in this document; we'll refer to them in following simply as capabilities.

HAL itself, assigns capabilities on device detection time by inspecting the device class (if available, it depends on the bus type) and looking at information from the operating system and the hardware itself.

User mode drivers such as libgphoto2 and sane provides device information to merge information about devices they can drive. As such, device objects represent an USB interface gain additional properties such as ''scanner'' or ''camera''.

Having a capability also means that part of the property namespace, prefixed with the capability name, will be populated with more specific information about the capability. Indeed, some properties may even be required such that applications and device libraries have something to expect. For instance, the capability for being a MP3 player may require properties defining what audio formats the device support (e.g. Ogg and MP3), whether it support recording of audio, and how to interact with the device. For example, the latter may specify ''USB Storage Device'' or ''proprietary protocol, use libfooplayer''.

Finally, capabilities have an inheritance scheme, e.g. if a device has a capability foo.bar, it must also have the capability foo.

Chapter 2. Device Information Files

Table of Contents

Matching
Merging
Search Paths

Device information files (.fdi files is a shorthand) are used to merge arbitrary properties onto device objects. The way device information files works is that once all device properties are merged onto a device object it is tried against the set of installed device information files. Device information files are used for both merging facts and policy settings about devices.

Matching

Each device information file got a number of <match key="some_property" [string|int|bool|..]="required_value" > directives that is tested against the properties of the device object. If all the match directives passes then the device information can include <[merge|append|prepend|addset] key="some_property" type="[string|int|bool|..]"> directives to respectively merge new properties or append to existing properties on the device object. It's important to emphasize that any previously property stemming from device detection can be overridden by a device information file.

The <match>, <merge>, <append>, <prepend> and <addset> directives always requires the key attribute which must be either a property name on the device object in question or a path to a property on another device object. The latter case is expressed either through direct specification of the UDI, such as /org/freedesktop/Hal/devices/computer:foo.bar or indirect references such as @info.parent:baz where the latter means that the device object specified by the UDI in the string property info.parent should be used to query the property baz. It is also possible to use multiple indirections, e.g. for a volume on a USB memory stick the indirection @block.storage_device:@storage.originating_device:usb.vendor_id will reference the usb.vendor_id property on the device object representing the USB interface.

When the property to match have been determined a number of attributes can be used within the <match> tag:

string - match a string property; for example <match key="foo.bar" string="baz"> will match only if 'foo.bar' is a string property assuming the value 'baz'.
string_outof - work like string but the match is done against a list of strings separated by ';'. For example: <match key="system.hardware.product" string_outof="Satellite A30;Portable PC"> In this example the line matches if system.hardware.product is exactly 'Satellite A30' or 'Portable PC'.
int - match an integer property
int_outof - work like int but the match is done against a list of integer separated by ';'. For example: <match key="usb.product_id" int_outof="0x1007;0x1008;0x1009"> In this example the line matches if usb.product_id is 0x1007, 0x1008 or 0x1009.
uint64 - match property with the 64-bit unsigned type
bool - match a boolean property
double - match a property of type double
exists - used as <match key="foo.bar" exists="true">. Can be used with 'true' and 'false' respectively to match when a property exists and it doesn't.
empty - can only be used on string or strlist properties with 'true' and 'false'. The semantics for 'true' is to match only when the string is non-empty.
is_ascii - matches only when a string property contain only ASCII characters. Can be used with 'true' or 'false'.
is_absolute_path - matches only when a string property represents an absolute path (the path doesn't have to exist). Can be used with 'true' or 'false'.
sibling_contains - can only be used with string and strlist (string list). For a string key this matches when a sibling item contains the (sub-)string in the same property. For a string list, this is if a string matches an item in the list.
contains - can only be used with string and strlist (string list). For a string key this matches when the property contains the given (sub-)string. For a string list this match if the given string match a item of the list.
contains_ncase - like contains but the property and the given key are converted to lowercase before check.
contains_not - can only be used with strlist (string list) and string properties. For a string list this match if the given string not match any of the item of the list (or the property is not set for the device). For a string this match of the property not contains the (sub-)string. You can use this attribute to construct if/else blocks together with e.g. contains.
contains_outof - like contains but can be used only with strings and the match is done against a list of (sub-)strings separated by ';'. For example: <match key="system.hardware.product" contains_outof="D600;D610;C540"> In this example the line matches if system.hardware.product contains D600, D610 or C540.
prefix - can only be used with string properties. Matches if property begins with the key.
prefix_ncase - like prefix but the property and the given key are converted to lowercase before the check.
prefix_outof - like prefix but the match is done against a list of prefixes separated by ';'. For example: <match key="system.hardware.product" prefix_outof="1860;2366;2371"> In this example the line matches if system.hardware.product starts with 1860, 2366 or 2371.
suffix - can only be used with string properties. Matches if property ends with the key.
suffix_ncase - like suffix but the property and the given key are converted to lowercase before the check.
compare_lt - can be used on int, uint64, double and string properties to compare with a constant. Matches when the given property is less than the given constant using the default ordering.
compare_le - like compare_lt but matches when less than or equal.
compare_gt - like compare_lt but matches when greater than.
compare_ge - like compare_lt but matches when greater than or equal.
compare_ne - like compare_lt but matches when not equal.

Merging

The <merge>, <append>, <prepend> and <addset> directives all require the type attribute which specifies what to merge. The following values are supported

string - The value is copied to the property. For example <merge key="foo.bar" type="string">baz</merge> will merge the value 'baz' into the property 'foo.bar'.
strlist - For <merge> the value is copied to the property and the current property will be overwritten. For <append> and <prepend> the value is append or prepend to the list as new item. For <addset> the strlist is treated as a set and the value is appended if, and only if, the value doesn't exist already. Usage of <copy_property> overwrite the complete list with the value of the given property to copy from.
bool - Can merge the values 'true' or 'false'
int - Merges an integer
uint64 - Merges an unsigned 64-bit integer
double - Merges a double precision floating point number
copy_property - Copies the value of a given property - supports paths with direct and indirect UDI's. For example <merge key="foo.bar" type="copy_property">@info.parent:baz.bat</merge> will merge the value of the property baz.bat on the device object with the UDI from the property info.parent into the property foo.bar on the device object being processed.

The <remove>, directive require only a key and can be used with all keys. For strlist there is additionally a special syntax to remove a item from the string list. For example to remove item 'bla' from property 'foo.bar': <remove key="foo.bar" type="strlist">bla</remove>

Search Paths

Device Information files are read from two directories

/usr/share/hal/fdi - for files provided by packages
/etc/hal/fdi - for files provided by the system administrator / user

in exactly that order. This means that the files provided by the system administrator will be processed last such that they can overwrite / change properties caused by the device information files provided by packages. The following directory structure is used in /usr/share/hal/fdi

information - device information files used to merge device information
- 10freedesktop - included with the hal package
- 20thirdparty - from a 3rd party, not included in hal package
policy - device information files to merge policy properties such as addons or callouts.
- 10osvendor - included with the hal package
- 20thirdparty - from a 3rd party, not included in hal package
preprobe - device information files read before probing devices
- 10osvendor - included with the hal package
- 20thirdparty - from a 3rd party, not included in hal package

As evident, third party packages should drop device information files in

/usr/share/hal/fdi/information/20thirdparty
/usr/share/hal/fdi/policy/20thirdparty
/usr/share/hal/fdi/preprobe/20thirdparty

The /etc/hal/fdi tree uses this layout

information - device information files used to merge device information
policy - device information files to merge policy properties such as addons or callouts.
preprobe - device information files to read before probing devices

All device information files are matched for every hal device object in the following order.

When a device is discovered, the preprobe device information files (e.g. all files from /usr/share/hal/fdi/preprobe and /etc/hal/fdi/preprobe) are processed.
Typically, this class of device information files is used to tell HAL to leave the device alone by setting the bool property info.ignore to TRUE. It can also be used to run programs, preprobe callouts, prior to normal device investigation.
HAL now runs the preprobe callouts.
HAL now probes/investigates the device.
All the information device information files (e.g. all files from /usr/share/hal/fdi/information and /etc/hal/fdi/information) are processed.
These device information files are typically used to associate extra information with a device object.
All the policy policy information files (e.g. all files from /usr/share/hal/fdi/policy and /etc/hal/fdi/policy) are processed.
These device information files are typically used to associate callouts and addons with a device object.
HAL now runs the callouts, starts addons, and then finally announces the device on the system message bus.

Chapter 3. Access Control

Table of Contents

Device Files
D-Bus Interfaces

Access to hardware by unprivileged users is traditionally granted in two ways either by granting access to the special device file or allowing access through another process, using IPC acting on behalf of the user. HAL follows the latter model and uses the system-wide message bus (D-Bus) as the IPC mechanism. In addition, HAL has support for modifying the ACL's (access control lists) on a device file to grant/revoke access to users based on several criteria.

Device Files

If HAL is built with --enable-acl-management (requires both --enable-console-kit and --enable-policy-kit) then ACL's on device objects with the capability access_control are automatically managed according to the properties defined in the section called “ access_control namespace ”. In addition, for this configuration, HAL ships with a device information file (normally installed in /usr/share/hal/fdi/policy/10osvendor/20-acl-management.fdi) that merges this capability on device objects that are normally accessed by unprivileged users through the device file. This includes e.g. sound cards, webcams and other devices but excludes drives and volumes as the latter two are normally accessed by a user through mounting them into the file system.

HAL uses PolicyKit to decide what users should have access according to PolicyKit configuration; see the PolicyKit privilege definition file /etc/PolicyKit/privileges/hal-device-file.priv on a system with HAL installed for the default access suggested by the HAL package and/or OS vendor.

In addition, 3rd party packages can supply device information files to specify (via the access_control.grant_user and access_control.grant_group properties) that a given user or group should always have access to a device file. This is useful for system-wide software (such as AV streaming management) that runs as an unprivileged system user. This interface is supposed to be stable so 3rd party packages can depend on it.

D-Bus Interfaces

If HAL is built without ConsoleKit support (e.g. without --enable-console-kit) access to the various D-Bus interfaces that provides mechanisms is only protected by the D-Bus security configuration files (e.g. using at_console to restrict to console user on Red Hat systems) and, in certain cases, restricted to the super user.

If ConsoleKit support is enabled, access to D-Bus interfaces is currently hardcoded to only allow active users at the system console. If PolicyKit support is enabled, the PolicyKit library will be in charge of determining access; see the PolicyKit privilege definition files in /etc/PolicyKit/privileges on a system with HAL installed for the default access suggested by the HAL package and/or OS vendor.

Chapter 4. Locking

Table of Contents

Overview
Guidelines

As HAL is a mechanism that enables programs in a desktop session to enforce the policy of the users choice, unexpected things can happen. For example, if the user is in the middle of partitioning a disk drive, it is desirable to keep the desktop from mounting partitions that have not yet been prepared with a suitable file system. In fact, in such a situation data loss may be the result if a volume have an old file system signature indicating it's mountable and, simultenously, another tool is writing to the raw block device. The mechanism that automounters use, HAL, provides locking primitives to avoid this.

Further, for multi-user systems, several desktop sessions may run on a system each on their own display. Suppose that one session becomes idle and the power management daemon in that session decides to suspend the system according to user preferences in the idle session. The result is that users at other seats will see the system suspend and this is not desirable. The power management daemons in all sessions need to cooperate to ensure that the system only suspends when e.g. all sessions are idle or not at all. The mechanism that each power management daemon uses, HAL, provides locking primitives that can be used to achieve this.

Overview

HAL provides a mechanism to lock a specific D-Bus interface either for a specific device or for all the devices the caller have access to.

The former is achieved by using the AcquireInterfaceLock() and ReleaseInterfaceLock() methods on the org.freedesktop.Hal.Device interface that every device object implements (see the section called “org.freedesktop.Hal.Device interface”). By using this API, a caller can prevent any other caller from invoking methods on the given interface for the given device object - other callers will simply see the org.freedesktop.Hal.Device.InterfaceLocked exception if they attempt to invoke a method on the given interface on the given device. The locker can specify whether the lock is exclusive meaning if multiple clients clients can hold the lock or if only one client can hold the lock at one time. If a client don't have access to the interface of the device, attempts to lock will fail with a org.freedesktop.Hal.PermissionDenied exception. If a client loses access to a device (say, if his session is switched away from using fast user switching) while holding a lock, he will lose the lock; this can be tracked by listening to the InterfaceLockReleased signal.

All local clients, whether they are active or not, can always lock interfaces on the root computer device object (this doesn't mean that they are privileged to use the interfaces though) - the rationale is that this device object represents shared infrastructure, e.g. power management, and even inactive sessions needs to participate in managing this.

If another client already holds a lock exclusively, attempts from other clients to acquire the lock will fail with the org.freedesktop.Hal.Device.InterfaceAlreadyLocked exception even if they have access to the device.

In addition, a client may opt to lock all devices that he got access to by using the AcquireGlobalInterfaceLock() and ReleaseGlobalInterfaceLock() methods on the org.freedesktop.Hal.Manager interface on the /org/freedesktop/Hal/Manager object (see the section called “org.freedesktop.Hal.Manager interface”). Global interface locks can also be obtained exclusively if the caller so desires. Unlike per-device interface locking, it is not checked at locking time whether the locker have access to a given device; instead checking is done when callers attempt to access the interface.

The algorithm used for determining if a caller is locked out is shown below. A caller A is locked out of an interface IFACE on a device object DEVICE if, and only if,

Another caller B is holding a lock on the interface IFACE on DEVICE and A don't have either a global lock on IFACE or a lock on IFACE on DEVICE; or
Another caller B is holding the global lock on the interface IFACE and B has access to DEVICE and and A don't have either a global lock on IFACE or a lock on IFACE on DEVICE.

In other words, a caller A can grab a global lock, but that doesn't mean A can lock other clients out of devices that A doesn't have access to. Specifically a caller is never locked out if he has locked an interface either globally or on the device in question. However, if two clients have a lock on a device, then both can access it. To ensure that everyone is locked out, a caller needs to use an exclusive lock.

Note that certain interfaces will also check whether other locks are being held on other device objects. This is specified on a per-interface basis in Chapter 6, D-Bus interfaces.

If a process holding locks disconnects from the system bus, the locks being held by that process will be released.

Guidelines

Locking is only useful if applications requiring exclusive access actually use the locking primitives to cooperate with other applications. Here is a list of guidelines.

Disk Management / Partitioning
In order to prevent HAL-based automounters from mounting partitions that are being prepared, applications that access block devices directly (and pokes the kernel to reload the partitioning table) should lock out automounters by either a) obtaining the org.freedesktop.Hal.Device.Storage lock on each drive being processed; or b) obtaintaing the global org.freedesktop.Hal.Device.Storage lock. This includes programs like fdisk, gparted, parted and operating system installers. See also the section called “org.freedesktop.Hal.Device.Volume interface” and the hal-lock(1) program and manual page.
Power Management
Typically, a desktop session includes a session-wide power management daemon that enforces the policy of the users choice, e.g. whether the system should suspend to ram on lid close, whether to hibernate the system after the user being idle for 30 minutes and so on. In a multi-user setup (both fast user switching and multi-seat), this can break in various interesting ways unless the power management daemons cooperate. Also, there may be software running at the system level who will want to inhibit a desktop session power management daemon from suspending / shutting down.
- System-level software that do not wish to be interrupted by the effect of someone calling into the org.freedesktop.Hal.Device.SystemPowerManagement interface MUST hold the org.freedesktop.Hal.Device.SystemPowerManagement lock non-exclusively on the root computer device object. For example, the YUM software updater should hold the lock when doing an RPM transaction.
In addition, any power management session daemon instance
- ... MUST hold the org.freedesktop.Hal.Device.SystemPowerManagement lock non-exclusively on the root computer device object unless it is prepared to call into this interface itself. This typically means that the PM daemon instance simply acquires the lock on start up and releases it just before it calls into the org.freedesktop.Hal.Device.SystemPowerManagement interface. In other words, the PM daemon instance needs to hold the lock exactly when it doesn't want other PM daemon instances to call into the org.freedesktop.Hal.Device.SystemPowerManagement interface. This means that if the user have configured the PM daemon instance to go to sleep after 30 minutes of inactivity, the lock should be released then.
- ... MUST not hold the lock when the session is inactive (fast user switching) UNLESS an application in the session have explicitly called Inhibit() on the org.freedesktop.PowerManagement D-Bus session bus interface of the PM daemon.
- ... MUST check that no other process is holding the lock (using the IsLockedByOthers method on the standard org.freedesktop.Hal.Device interface) before calling into the org.freedesktop.Hal.Device.SystemPowerManagement interface. If another process is holding the lock, it means that either 1) another session is not prepared to call into the org.freedesktop.Hal.Device.SystemPowerManagement interface; OR 2) some system-level software is holding the lock. The PM daemon instance MUST respect this by not calling into the org.freedesktop.Hal.Device.SystemPowerManagement interface itself.
However, any Power management daemon instance
- ... MAY prompt the user, if applicable, to ask if she still wants to perform the requested action (e.g. call into the org.freedesktop.Hal.Device.SystemPowerManagement interface) despite the fact that another process (possibly from another user) is indicating that it does not want the system to e.g. suspend. Only if the user agrees, the power management instance should call into the org.freedesktop.Hal.Device.SystemPowerManagement interface. Typically, it's only useful to prompt the user with such questions if the request to call into the org.freedesktop.Hal.Device.SystemPowerManagement interface originates from user input, e.g. either a hotkey, the user clicking a suspend button in the UI or an application invoking the Suspend() method on the org.freedesktop.PowerManagement D-Bus session interface of the PM daemon.
- ... MAY ignore that other processes are holding the lock and call into the org.freedesktop.Hal.Device.SystemPowerManagement interface anyway, but ONLY if if the request to call into the org.freedesktop.Hal.Device.SystemPowerManagement interface originated from e.g. lid close, critically low battery or other similar conditions.
- ... MAY still call SetPowerSave() on the org.freedesktop.Hal.Device.SystemPowerManagement interface even if other processes are holding the lock.

Chapter 5. Device Properties

Table of Contents

General Properties

info namespace
linux namespace
Callouts
Addons
Singleton Addons
Method calls

Subsystem-Specific Properties

pci namespace
serial namespace
pnp namespace
modem namespace
usb_device namespace
usb namespace
platform namespace
ide_host namespace
ide namespace
scsi_host namespace
scsi namespace
ieee1394_host namespace
ieee1394_node namespace
ieee1394 namespace
mmc_host namespace
mmc namespace
sdio namespace
ccw namespace
ccwgroup namespace
iucv namespace
block namespace
xen namespace
bluetooth_hci namespace
bluetooth_acl namespace
bluetooth_sco namespace
drm namespace
ps3_system_bus namespace
virtio namespace
virtio namespace
vmbus namespace

Functional Properties

system namespace
volume namespace
volume.disc namespace
storage namespace
storage.cdrom namespace
storage.linux_raid namespace
net namespace
net.80203 namespace
net.80211 namespace
net.bridge namespace
net.bluetooth namespace
net.irda namespace
net.80211control namespace
input namespace
input.keys namespace
input.keypad namespace
input.keyboard namespace
input.mouse namespace
input.switch namespace
input.joystick namespace
input.tablet namespace
input.keymap namespace
input.xkb namespace
pcmcia_socket namespace
printer namespace
portable_audio_player namespace
alsa namespace
oss namespace
camera namespace
scanner namespace
laptop_panel namespace
ac_adapter namespace
battery namespace
button namespace
processor namespace
light_sensor namespace
PDA namespace
power_management namespace
tape namespace
killswitch namespace
video4linux namespace
video4linux.video_capture namespace
video4linux.video_output namespace
video4linux.video_overlay namespace
video4linux.audio namespace
video4linux.tuner namespace
video4linux.radio namespace
of_platform namespace

Misc. Properties

access_control namespace

Deprecated Properties

Properties are arranged in a namespaces using ''.'' as a separator and are key/value pairs. The value may assume different types; currently int32, double, bool, UTF8 strings and UTF8 string lists are supported. The key of a property is always an ASCII string without any whitespace. When a property changes, HAL will emit a D-Bus signal that applications can catch.

General Properties

The section represents properties that aren't tied to either physical or functional characteristics of what the device object represents.

info namespace

The info namespace contain properties that can be considered metadata about device objects. These properties are always available.

Key (type)	Values	Mandatory	Description
`info.subsystem` (string)	pci, usb, ide_host, ide, block, usb, usbif, scsi_host, scsi	Yes	Describes what subsystem the device is connected to
`info.udi` (string)	example: /org/freedesktop/Hal/devices/pci_10ec_8139	Yes	The HAL unique device id
`info.capabilities` (strlist)	example: 'block, storage, storage.cdrom'	No	A string list of capabilities describing what the devices does
`info.category` (string)	example: storage.cdrom	No	The prominent capability describing what the device is
`info.product` (string)	examples: ''SleekKeyboard'', ''MouseMan 2003'', ''Volume'', ''LS-120 SLIM3 00 UHD Floppy''	No	The name of the device; should not be used in any UI; use subsystem / capability specific properties instead.
`info.vendor` (string)	examples: Logitch, Mustek	No	The name of the vendor of the device; should not be used in any UI; use subsystem / capability specific properties instead.
`info.parent` (string)	example: /org/freedesktop/Hal/devices/computer	Yes, for all non-root device objects	The UDI of the device object that this device object is connected to.
`info.locked` (bool)		No	If this property is available and set to `TRUE` it means that a process is using the device that the hal device object in question represents and no other process should attempt to use or configure the device. The lock is only advisory.
`info.locked.reason` (string)	example: ''The optical drive is currently being used to record a CD-RW disc.''	Only available if `info.locked` is set to `TRUE`.	A localized text suitable for UI display
`info.locked.dbus_service` (string)	example: :1.278	Only available if `info.locked` is set to `TRUE`.	The base D-BUS service of the process holding the lock.
`info.is_recalled` (bool)		No	This is set if the hardware may be recalled and should be checked for any potential problem.
`info.recall.vendor` (string)	Dell, Sony, HP, Panasonic, etc.	Yes, if `info.is_recalled` is TRUE	The vendor responsible for the hardware recall.
`info.recall.website_url` (string)		Yes, if `info.is_recalled` is TRUE	Users should check this website for more details and if their hardware may affected by any possible fault.

linux namespace

The linux namespace contain properties that can be considered metadata about device objects in Linux systems. These properties are available only on Linux systems.

Key (type)	Values	Mandatory	Description
`linux.subsystem` (string)	pci, usb, ide_host, ide, block, usb, usbif, scsi_host, scsi	Yes	Describes what Linux subsystem the device is connected to. This can differ from `info.subsystem`
`linux.sysfs_path` (string)	for example: /sys/class/sound/seq	No	Path to the devuce in the sysfs. Could also be `*.linux.sysfs_path` depending on the subsystem in some cases.
`linux.device_file` (string)	for example: /dev/snd/pcmC0D1c or /dev/input/event6	No	Path to the corresponding device file in /dev/ on linux system.
`info.linux.driver` (string)	for example: pcspkr, vesafb, serial8250	No	Name of the driver/module corresponding to the device and/or subsystem.
`linux.hotplug_type` (int)		Yes	The type of hotplug event in a linux system.
`linux.acpi_type` (int)		No (except for ACPI devices)	The type of ACPI device. Normaly only for HAL internal use.
`linux.apm_type` (int)		No (except for APM devices)	The type of APM device. Normaly only for HAL internal use.
`linux.pmu_type` (int)		No (except for PMU devices)	The type of PMU device. Normaly only for HAL internal use.

Callouts

Callouts are programs invoked when the device object are added and removed. As such, callouts can be used to maintain system-wide policy (that may be specific to the particular OS) such as changing permissions on device nodes, updating the systemwide /etc/fstab file or configuring the networking subsystem.

There are three different classes of callouts. A callout involves sequentially invoking all executable programs in the string list in listed order.

All callouts are searched for and execute in a minimal environment. In addition, the UDI of the device object is exported in the environment variable UDI. All properties of the device object are exported in the environment prefixed with HAL_PROP_. If a device is added or removed is exported in the environment variable HALD_ACTION. The search path for the callout includes the following paths:

$libexecdir (typically /usr/libexec (e.g. Red Hat) or /usr/lib/hal (e.g. Debian))
$libdir/hal/scripts (typically /usr/lib/hal/scripts or /usr/lib64/hal/scripts)
$bindir/ (typically /usr/bin)

including $PATH the HAL daemon was started with during system initialization. Depending on the distribution, this typically includes /sbin, /usr/sbin, /bin, /usr/sbin. If the program to run is not found in any of these paths, the it will not run even if the given path is absolute. To be portable across operating systems, third party packages providing callouts must therefore only use $libdir/hal/scripts.

If ConsoleKit support is enabled, the variables CK_NUM_SEATS (number of seats), CK_NUM_SESSIONS (number of sessions), CK_SEATS (tab sep. list of seat-id's), CK_SEAT_seat-id (tab sep. list of session-id's for a seat), CK_SEAT_NUM_SESSIONS_seat-id (number of sessions on a seat), CK_SESSION_SEAT_session-id (the seat that a session belongs to) and CK_SESSION_IS_ACTIVE_session-id (whether a given session is active) and CK_SESSION_UID_session-id (the user of the session) and CK_SESSION_IS_LOCAL_session-id (whether a session is local), CK_SESSION_HOSTNAME_session-id (host name of session's display if it's not local), will be exported as well. Example:

CK_NUM_SEATS=1
CK_NUM_SESSIONS=2
CK_SEATS=Seat1
CK_SEAT_Seat1=Session1  Session3
CK_SEAT_NUM_SESSIONS_Seat1=2
CK_SESSION_IS_ACTIVE_Session1=true
CK_SESSION_IS_ACTIVE_Session3=false
CK_SESSION_IS_LOCAL_Session1=true
CK_SESSION_IS_LOCAL_Session3=true
CK_SESSION_SEAT_Session1=Seat1
CK_SESSION_SEAT_Session3=Seat1
CK_SESSION_UID_Session1=500
CK_SESSION_UID_Session3=501

Note that all ConsoleKit object paths given are just base names; the real D-Bus object path can be reconstructed by appending /org/freedesktop/ConsoleKit/ prepended to the given identifer.

The HAL daemon is not suspended while callouts are executing. Thus, callouts can communicate with the HAL daemon using the D-BUS network API. Hence, one application of callouts is to merge or modify properties on a device object.

To reduce round trips and increase privacy, callouts can (and should) communicate with the HAL daemon using a peer to peer D-Bus connection specified by the HALD_DIRECT_ADDR environment variable. There is convience API in libhal to do this.

Key (type)	Mandatory	Description
`info.callouts.add` (string list)	No	A string list with the programs which should be executed (with `HALD_ACTION=add`) when the device is added to the GDL (global device list) but just before it is announced through the D-BUS network API.
`info.callouts.remove` (string list)	No	A string list with the programs that should be executed (with `HALD_ACTION=remove`) when the device is removed from the GDL (global device list). The device isn't removed before the last callout has finished.
`info.callouts.preprobe` (string list)	No	A string list with the programs that should be executed (with `HALD_ACTION=preprobe`) before the device is probed (e.g. investigated) and can be used to avoid causing unnecessary I/O.
`info.callouts.session_add` (string list)	No	A string list with all programs that should be executed (with `HALD_ACTION=session_add`) when a session is added. Can only be set on the root computer device object. The environment also contains the variables `HALD_SESSION_ADD_SESSION_ID`, `HALD_SESSION_ADD_SESSION_UID` and `HALD_SESSION_ADD_SESSION_IS_ACTIVE` to identify the session. This is only used when HAL is built with ConsoleKit support.
`info.callouts.session_remove` (string list)	No	A string list with all programs which should be executed (with `HALD_ACTION=session_remove`) when a session is removed. Can only be set on the root computer device object. The environment also contains the variables `HALD_SESSION_REMOVE_SESSION_ID`, `HALD_SESSION_REMOVE_SESSION_UID` and `HALD_SESSION_REMOVE_SESSION_IS_ACTIVE` to identify the session. This is only used when HAL is built with ConsoleKit support.

Addons

Addons are programs that run for the life time of the device object. They are searched for and execute in the same environment as callouts (e.g. with HAL_PROP_* set in the environment to represent the device properties) and are launched just before the device is announced on D-Bus (but just after the last add callouts have finished). When the device object goes away, HAL will send a SIGTERM to the process.

Key (type)	Values	Mandatory	Description
`info.addons` (strlist)		No	List of programs to run when device is added. Each program will need to call the `AddonIsReady()` method in order for the device to show up on D-Bus.

Singleton Addons

Singleton Addons are programs that are started by HAL to handle a set of devices. They are identified by the command line used to start them. They MUST implement the org.freedesktop.Hal.SingletonAddon interface. on the path /org/freedesktop/Hal/Singleton path on the direct connection to the HAL daemon.

When a device is added with an info.addons.singleton string list key, the elements of that key are used as the command line to start the singleton if the singleton is not already running. Once the singleton has called SingletonAddonIsReady on org.freedesktop.Hal.Manager interface, it will receive DeviceAdded calls on its org.freedesktop.Hal.SingletonAddon interface for all devices that have its commandline in info.addons.singletona.

If a device is added and the singleton specified in info.addons.singleton is already running, the singleton will recieve DeviceAdded on its org.freedesktop.Hal.SingletonAddon interface for that new device.

When a device is removed that is being handled by a singleton, the singleton will recieve DeviceRemoved on org.freedesktop.Hal.SingletonAddon . When it is no longer handling any more devices it should exit cleanly.

Key (type)	Values	Mandatory	Description
`info.addons.singleton` (strlist)		No	A list of commandlines for singleton addons which should service this device.

Method calls

Method calls on a specific interface on a device object can be implemented by the HAL daemon running a program. Note that this is not the only way to implement support for method calls; if you expect a lot of method calls it is preferable to implement an addon and use the ClaimInterface() API since it reduces the overhead of spawning a process and it can handle both complex incoming and return types as well. See the section called “org.freedesktop.Hal.Device interface” for details on claiming interfaces via an addon..

Note that method calls implemented via running a program are limited to the return type being an a signed 32-bit integer (this will change in a future release). The incoming parameters are limited to only basic types and arrays of strings. The parameters are passed via stdin using a textual representation. As such, there is a lot of overhead with handling method calls by spawning programs and as such it should only be used for situtations where the nature of the method call is that it will not be frequently used.

As with addons, method calls are searched for and execute in the same minimal environment as callouts (e.g. with HAL_PROP_* set in the environment to represent the device properties) and in addition the environment variables HAL_METHOD_INVOKED_BY_UID (the uid of the caller) and HAL_METHOD_INVOKED_BY_SYSTEMBUS_CONNECTION_NAME (the unique system bus connection name of the caller) are set. Additionally, if HAL is built with ConsoleKit support, HAL_METHOD_INVOKED_BY_PID and HAL_METHOD_INVOKED_BY_SELINUX_CONTEXT (but only if the running system have SELinux enabled) will be set. If HAL itself, or a HAL addon, is invoking a method, then these variables will not be present. Here's an example

HAL_METHOD_INVOKED_BY_UID=500
HAL_METHOD_INVOKED_BY_PID=22553
HAL_METHOD_INVOKED_BY_SELINUX_CONTEXT=user_u:system_r:unconfined_t
HAL_METHOD_INVOKED_BY_SYSTEMBUS_CONNECTION_NAME=:1.138

In addition, with ConsoleKit support, HAL_METHOD_INVOKED_BY_SESSION will be set to (the basename) of the ConsoleKit session object path but only if the caller is in a session. The method handler can then use the previously mentioned CK_SESSION_* to learn everything about the context of the caller.

Key (type)	Values	Mandatory	Description
`info.interfaces` (strlist)		No	A list of D-Bus interfaces that the device object supports apart from the standard `org.freedesktop.Hal.Device` interface.
`<iface>.method_names` (strlist)	example: `'Foo', 'Bar', 'Baz'`	No	If a D-Bus interface is implemented by executing a program for every method, this property contains an ordered list of the method names.
`<iface>.method_argnames` (strlist)	example: `'foo_arg1 foo_arg2', '', 'baz_arg1'`	No	This property contains the names of the arguments for each method. Each entry is a white-space separated list for that particular method.
`<iface>.method_signatures` (strlist)	example: `'si', '', 'as'`	No	This property contains the D-Bus signature for each method. The signature should only cover incoming arguments; each method is defined as returning an integer.
`<iface>.method_execpaths` (strlist)	example: `'foo-binary', 'bar-binary', 'baz-binary'`	No	This property contains the name of the program to execute when this method is called. The return code of the program will be passed as the integer result to the D-Bus caller. If a program wants to return an error, it just needs to write two lines to stderr; the first line is the exception name to throw and the second line is the exception detail.

Items in the <iface>.* clearly must correspond with each other. The whole mechanism is best explained by an example:

info.interfaces = {'org.freedesktop.Hal.Device.Volume'}
org.freedesktop.Hal.Device.Volume.method_argnames = {'mount_point fstype extra_options', 'extra_options', 'extra_options'}
org.freedesktop.Hal.Device.Volume.method_execpaths = {'hal-storage-mount', 'hal-storage-unmount', 'hal-storage-eject'}
org.freedesktop.Hal.Device.Volume.method_names = {'Mount', 'Unmount', 'Eject'}
org.freedesktop.Hal.Device.Volume.method_signatures = {'ssas', 'as', 'as'}

which, for example, shows that the Mount() method on the interface org.freedesktop.Hal.Device.Volume takes three arguments: mount_point (a string), fstype (a string) and extra_options (an array of strings).

Subsystem-Specific Properties

In this section properties for device objects that represent addressable hardware is described. Availability of these depends on the value of the info.subsystem property. These properties are not of particular interest to application developers, instead they are useful for libraries and userspace drivers that needs to interact with the device given a UDI. Knowledge of various subsystem-specific technologies is assumed for this section to be useful.

pci namespace

This namespace contains properties for device objects representing functions on devices on a PCI bus. These properties are available exactly when info.subsystem equals pci.

Key (type)	Values	Mandatory	Description
`pci.device_class` (int)	example: 3	Yes	Device Class
`pci.device_subclass` (int)	example: 0	Yes	PCI Device Sub Class
`pci.device_protocol` (int)	example: 0	Yes	Device Protocol
`pci.product_id` (int)	example: 0x4c4d	Yes	Product ID
`pci.vendor_id` (int)	example: 0x1002	Yes	Vendor ID
`pci.subsys_product_id` (int)	example: 0x009e	Yes	Subsystem product id
`pci.subsys_vendor_id` (int)	example: 0x1028	Yes	Subsystem vendor id
`pci.linux.sysfs_path` (string)	example: /sys/devices/pci0000:00/0000:00:01/0000:01:00.0	Yes (only on Linux)	Equals `linux.sysfs_path`
`pci.product` (string)	Rage Mobility P/M AGP 2x	No	Name of the product per the PCI database
`pci.vendor` (string)	ATI Technologies Inc	No	Name of the vendor per the PCI database
`pci.subsys_product` (string)	Inspiron 7500	No	Name of the subsystem product per the PCI database
`pci.subsys_vendor` (string)	Dell Computer Corporation	No	Name of the subsystem vendor per the PCI database

(FIXME: Some key PCI information (bus, slot, port, function etc.) is missing here)

serial namespace

Device objects that represent serial devices (e.g. /dev/ttyS* or /dev/ttyUSB*).

Key (type)	Values	Mandatory	Description
`serial.originating_device` (string)	example: `/org/freedesktop/Hal/devices/pnp_PNP0501`	Yes	UDI of the device the serial device is bound to.
`serial.device` (string)	example: /dev/ttyS0	Yes	The device node to access the OSS device.
`serial.port` (int)	example: 0	Yes	The port number of the device, based on the number in `serial.device`
`serial.type` (string)	example: platform, usb, unknown	Yes	This property defines the type of the serial device.

pnp namespace

Device objects that represent Plug and Play (PnP) devices (e.g. System Board or PS/2 Port for PS/2-style Mice). For these devices info.subsystem is set to 'pnp'.

Key (type)	Values	Mandatory	Description
`pnp.id` (string)	example: PNP0a03 or SMCf010	Yes	This property contains the PnP ID of the device.
`pnp.description` (string)	example: 'ECP printer port'	No	Description from the pnp.ids file. Only available if: HAL was compiled with support for pnp.ids, if the file is available and if the ID was part of the file.
`pnp.serial.irq` (int)	example: 5	No	Only available if the PnP device is a serial device (as e.g. serial Wacom Tablet devices). Contains the prefered irq of the device.
`pnp.serial.port` (string)	example: 0x200	No	Only available if the PnP device is a serial device (as e.g. serial Wacom Tablet devices). contains info about the prefered serial port of the device.
`pnp.serial.baud_base` (int)	example: 38400	No	Only available if the PnP device is a serial device (as e.g. serial Wacom Tablet devices). Contains info about the needed baud_base to setup the device correctly.

modem namespace

Serial device objectes that are known to be modems should also gain the modem capability in their info.capabilities list. Modem device objects must also be serial device objects.

Key (type)	Values	Mandatory	Description
`modem.command_sets` (string)	example: GSM-07.07, GSM-07.05	Yes	This property defines the command sets the modem device supports.
	IS-707-A	Yes	This modem supports the IS-707-A standard AT commands (commonly used by CDMA cellular devices). Implies V.250 support.
	GSM-07.07	Yes	This modem supports the GSM-07.07 standard AT commands (commonly used by GSM-based cellular devices). Implies V.250 support.
	GSM-07.05	Yes	This modem supports the GSM-07.05 standard AT commands (commonly used by GSM-based cellular devices). Implies V.250 support.
	ITU-V.250	Yes	This modem supports the ITU V.250 standard AT commands (also known as Hayes-compatible).

usb_device namespace

For device objects representing USB devices the property info.subsystem will be usb_device, and the following properties will be available. Note that the corresponding USB interfaces are represented by separate device objects as children.

Key (type)	Values	Mandatory	Description
`usb_device.bus_number` (int)	example: 1	Yes	The USB bus the device is attached to
`usb_device.configuration_value` (int)	example: 1	Yes	The current configuration the USB device is in; starting from 1
`usb_device.configuration` (int)	example: Bulk transfer configuration	No	Human-readable description of the current configuration the USB device is in
`usb_device.num_configurations` (int)	example: 1	Yes	Number of configurations this USB device can assume
`usb_device.device_class` (int)	example: 0	Yes	USB Device Class
`usb_device.device_subclass` (int)	example: 0	Yes	USB Device Sub Class
`usb_device.device_protocol` (int)	example: 0	Yes	USB Device Protocol
`usb_device.is_self_powered` (bool)	example: false	Yes	The device, in the current configuration, is self powered
`usb_device.can_wake_up` (bool)	example: true	Yes	The device, in the current configuration, can wake up
`usb_device.max_power` (int)	example: 98	Yes	Max power drain of device, in mA
`usb_device.num_interfaces` (int)	example: 1	Yes	Number of USB Interfaces in the current configuration
`usb_device.num_ports` (int)	example: 0	Yes	Number of ports on a hub. Zero for non-hubs
`usb_device.port_number` (int)	example: 1	Yes	The port number on the parent hub that the device is attached to, starting from 1
`usb_device.speed` (double)	examples: 1.5, 12.0, 480.0	Yes	Speed of device, in Mbit/s
`usb_device.version` (double)	examples: 1.0, 1.1, 2.0	Yes	USB version of device
`usb_device.level_number` (int)	example: 2	Yes	Depth in USB tree, where the virtual root hub is at depth 0
`usb_device.linux.device_number` (string)	example: 19	Yes (only on Linux)	USB Device Number as assigned by the Linux kernel
`usb_device.linux.parent_number` (string)	example: 19	Yes (only on Linux)	Device number of parent device as assigned by the Linux kernel
`usb_device.linux.sysfs_path` (string)	example: /sys/devices/pci0000:00/0000:00:07.2/usb1/1-1/1-1.1	Yes (only on Linux)	Equals `linux.sysfs_path`
`usb_device.product_id` (int)	example: 0x3005	Yes	USB Product ID
`usb_device.vendor_id` (int)	example: 0x04b3	Yes	USB Vendor ID
`usb_device.device_revision_bcd` (int)	example: 0x0100	Yes	Device Revision Number encoded in BCD with two decimals
`usb_device.serial` (string)		No	A string uniquely identifying the instance of the device; ie. it will be different for two devices of the same type. Note that the serial number is broken on some USB devices.
`usb_device.product` (string)	example: IBM USB HUB KEYBOARD	No	Name of the product per the USB ID Database
`usb_device.vendor` (string)	example: IBM Corp.	No	Name of the vendor per the USB ID Database

usb namespace

Device objects that represent USB interfaces, ie. when info.subsystem assumes usb, are represented by the properties below. In addition all the usb_device.* properties from the parent USB device is available in this namespace but only with the usb prefix instead of usb_device.

Key (type)	Values	Mandatory	Description
`usb.interface.class` (int)	example: 0x03	Yes	USB Class for the interface
`usb.interface.subclass` (int)	example: 0x01	Yes	USB Sub Class for this interface
`usb.interface.protocol` (int)	example: 0x01	Yes	USB Protocol for the interface
`usb.interface.description` (int)	example: SyncML interface	No	Human-readable description for the interface provided by the device
`usb.interface.number` (int)	example: 1	Yes	Number of this interface, starting from zero
`usb.linux.sysfs_path` (string)	example: /sys/devices/pci0000:00/0000:00:07.2/usb1/1-1/1-1.1/1-1.1:1.0	Yes (only on Linux)	Equals `linux.sysfs_path`

platform namespace

Devices that are built into the platform or present on busses that cannot be properly enumerated (e.g. ISA) are represented by device objects where info.subsystem equals platform. These kind of devices are commonly, somewhat incorrectly, called legacy devices.

Key (type)	Values	Mandatory	Description
`platform.id` (string)	example: serial	Yes	Device identification

ide_host namespace

The ide_host namespace is present for device objects where info.subsystem is set to ide_host. Such device objects represent IDE and ATA host adaptors for harddisks and optical drives as found in the majority of computer systems.

Key (type)	Values	Mandatory	Description
`ide_host.number` (int)		Yes	A unique number identifying the IDE host adaptor
`ide_host.linux.sysfs_path` (string)	example: /sys/devices/pci0000:00/0000:00:07.1/ide0	Yes (only on Linux)	Equals `linux.sysfs_path`

ide namespace

ATA and IDE drives are represented by device objects where info.subsystem equals ide. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`ide.host` (int)		Yes	Corresponds to `ide_host.host_number` of the `ide_host` device that is the parent of this device object
`ide.channel` (int)		Yes	Identifies the IDE channel of the host interface

scsi_host namespace

The scsi_host namespace is present for device objects where info.subsystem is set to scsi_host. Such device objects represent SCSI host adaptors for SCSI devices as found in some computer systems.

Key (type)	Values	Mandatory	Description
`scsi_host.host` (int)		Yes	A unique number identifying the SCSI host adaptor

scsi namespace

SCSI devices are represented by device objects where info.subsystem equals scsi. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`scsi.host` (int)		Yes	Corresponds to `scsi_host.host` of the `scsi_host` device that is the parent of this device object
`scsi.bus` (int)		Yes	SCSI channel number
`scsi.target` (int)		Yes	SCSI identifier number
`scsi.lun` (int)		Yes	SCSI Logical Unit Number
`scsi.type` (string)	Example: disk	Yes	SCSI device type
	cdrom		This is a SCSI cdrom device.
	comm		This is a SCSI communication device.
	disk		This is a SCSI disk device.
	medium_changer		This is a SCSI media changer (e.g. for CD/Tape).
	printer		This is a SCSI printer.
	processor		This is a SCSI processor device.
	raid		This is a SCSI raid device.
	scanner		This is a SCSI scanner.
	tape		This is a SCSI tape device.
	unknown		The type of this SCSI device is unknwon.

ieee1394_host namespace

Device objects with info.subsystem set to ieee1394_host represent IEEE 1394 host adaptors. The following properties are available for such device objects.

Key (type)	Mandatory	Description
`ieee1394_host.is_busmgr` (bool)	Yes	TODO
`ieee1394_host.is_irn` (bool)	Yes	TODO
`ieee1394_host.is_root` (bool)	Yes	TODO
`ieee1394_host.node_count` (int)	Yes	TODO
`ieee1394_host.nodes_active` (int)	Yes	TODO

ieee1394_node namespace

Device objects with info.subsystem set to ieee1394_node represent IEEE 1394 nodes on a IEEE 1394 bus. The following properties are available for such device objects.

Key (type)	Mandatory	Description
`ieee1394_node.capabilities` (int)	Yes	TODO
`ieee1394_node.guid` (int)	Yes	TODO
`ieee1394_node.nodeid` (int)	Yes	TODO
`ieee1394_node.vendor` (int)	Yes	TODO
`ieee1394_node.vendor_id` (int)	Yes	TODO

ieee1394 namespace

Device objects with info.subsystem set to ieee1394 represent IEEE 1394 devices. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`ieee1394.specifier_id` (int)		Yes	TODO

mmc_host namespace

Device objects with info.subsystem set to mmc_host represent MultiMediaCard or Secure Digital host adaptors. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`mmc_host.host` (int)		Yes	A unique number identifying the MMC/SD host adaptor

mmc namespace

Device objects with info.subsystem set to mmc represent MultiMediaCard or Secure Digital cards. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`mmc.cid` (string)	example: 0150415330303842413a1a8083003a9d	Yes	Card Identification Data register (unique for every card in existence)
`mmc.csd` (string)	example: 005d013213598067b6d9cfff1640002d	Yes	Card Specific Data register
`mmc.scr` (string)	example: 00a5000000410000	Only for SD cards	SD Card Register
`mmc.rca` (int)	example: 8083	Yes	Card bus address
`mmc.oem` (string)		Yes	Card OEM distributor
`mmc.date` (string)	example: 10/2003	Yes	Manufacturing date
`mmc.serial` (int)	example: 0x3a1a8083	Yes	Card serial number
`mmc.hwrev` (int)	example: 4	Yes	Hardware revision
`mmc.fwrev` (int)	example: 1	Yes	Firmware revision
`mmc.type` (string)	example: SDIO	No	Card type

sdio namespace

Device objects with info.subsystem set to sdio represent MultiMediaCard or Secure Digital cards with SDIO interface. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`sdio.rca` (int)	example: 8083	Yes	Card bus address
`sdio.card_id` (int)	example: 1	Yes	SDIO Class for the interface
`sdio.class_id` (int)	example: 0x03	Yes	SDIO Class for the interface
`sdio.product_id` (int)	example: 0x046a	Yes	Product ID
`sdio.vendor_id` (int)	example: 0x039d	Yes	Vendor ID
`sdio.product` (string)	SQN1130 WiMAX Network Card	No	Name of the product per the SDIO database
`sdio.vendor` (string)	Sequans Communications	No	Name of the vendor per the SDIO database

ccw namespace

Device objects that represent s390 ccw devices (when info.subsystem is set to ccw) are represented by the properties below.

Key (type)	Values	Mandatory	Description
`ccw.devtype` (string)	example: 1732/01	Yes	Device type/model or n/a
`ccw.cutype` (string)	example: 1731/01	Yes	Control unit type/model
`ccw.cmb_enable` (int)	example: 1	Yes	If channel measurements are enabled
`ccw.availability` (string)	example: good	Yes	Can be one of 'good', 'boxed', 'no path', or 'no device'
`ccw.online` (int)	example: 1	Yes	Online status
`ccw.bus_id` (string)	example: 0.0.f588	Yes	The device's bus id in sysfs
`ccw.subchannel.pim` (int)	example: 0x80	No	path installed mask
`ccw.subchannel.pam` (int)	example: 0x80	No	path available mask
`ccw.subchannel.pom` (int)	example: 0xff	No	path operational mask
`ccw.subchannel.chpid0..7` (int)	example: 0x40	No	channel path ids

The following properties describe ccw devices where linux.driver is either dasd-eckd or dasd-fba.

Key (type)	Values	Mandatory	Description
`ccw.dasd.use_diag` (int)	example: 0	Yes	If the device driver shall use diagnose calls to access the device
`ccw.dasd.readonly` (int)	example: 0	Yes	If the device can only be accessed readonly
`ccw.dasd.discipline` (string)	example: ECKD	No	The dasd discipline used to access the device

The following properties describe ccw devices where linux.driver is zfcp. They are only present when ccw.online = 1.

Key (type)	Values	Mandatory	Description
`ccw.zfcp.in_recovery` (int)	example: 0	Yes	Shows whether the adapter is currently in recovery
`ccw.zfcp.failed` (int)	example: 0	Yes	Shows whether the adapter is in failed state

The following properties describe ccw devices where linux.driver is of the form tape_3xxx .

Key (type)	Values	Mandatory	Description
`ccw.tape.state` (string)	example: IN_USE	Yes	The current status of the tape
`ccw.tape.operation` (string)	example: REW	Yes	A three-letter mnemonic of the current tape operation
`ccw.tape.medium_state` (string)	example: no medium	No	If `ccw.online = 1`, shows whether a tape is loaded
`ccw.tape.blocksize` (int)	example: 512	No	If `ccw.online = 1`, shows the blocksize used for reads and writes to the tape

The following properties describe ccw devices where linux.driver is 3270.

Key (type)	Values	Mandatory	Description
`ccw.3270.model` (int)	example: 3	Yes	The model of the device, determining rows and columns
`ccw.3270.rows` (int)	example: 32	Yes	The number of rows
`ccw.3270.columns` (int)	example: 80	Yes	The number of columns

ccwgroup namespace

Device objects that represent groups of ccw devices (when info.subsystem is set to ccwgroup have the properties specified below.

Key (type)	Values	Mandatory	Description
`ccwgroup.online` (int)	example: 1	Yes	Online status
`ccwgroup.bus_id` (string)	example: 0.0.f588	Yes	The device's bus id in sysfs

The following properties describe ccwgroup devices where linux.driver is qeth.

Key (type)	Values	Mandatory	Description
`ccwgroup.qeth.large_send` (string)	example: TSO	No	Whether large send is provided. Can be "no", "EDDP" (software) or "TSO" (hardware).
`ccwgroup.qeth.card_type` (string)	example: OSD_1000	Yes	Type of the card
`ccwgroup.qeth.checksumming` (string)	example: sw checksumming	No	The method used to checksum incoming packets
`ccwgroup.qeth.canonical_macaddr` (int)	example: 0	No	Specifies the token ring macaddress format. Not valid in layer2 mode and for ethernet devices.
`ccwgroup.qeth.broadcast_mode` (string)	example: broadcast_allrings	No	The scope of token ring broadcasts. Not valid in layer2 mode and for ethernet devices.
`ccwgroup.qeth.fake_broadcast` (int)	example: 0	No	Whether to fake broadcast capability. Not valid in layer2 mode.
`ccwgroup.qeth.fake_ll` (int)	example: 0	No	Whether to add a faked link level header to packets. Not valid in layer2 mode.
`ccwgroup.qeth.layer2` (int)	example: 0	No	Whether the card operates in layer 2 mode
`ccwgroup.qeth.portname` (string)	example: OSAPORT	No	The port name which has been specified for the card
`ccwgroup.qeth.portno` (int)	example: 0	No	The relative port number on the card
`ccwgroup.qeth.buffer_count` (int)	example: 16	Yes	Number of inbound buffers used
`ccwgroup.qeth.add_hhlen` (int)	example: 0	No	How much additional space is provided in the hardware header in skbs in front of packets
`ccwgroup.qeth.priority_queueing` (string)	example: always queue 2	No	Which priority queueing algorithm is to be used
`ccwgroup.qeth.route4` (string)	example: no	No	Whether the card has a routing functionality for ipv4. Not valid in layer2 mode.
`ccwgroup.qeth.route6` (string)	example: no	No	Whether the card has a routing functionality for ipv6. Not valid in layer2 mode.
`ccwgroup.qeth.state` (string)	example: UP (LAN ONLINE)	Yes	The device's current state

The following properties describe ccwgroup devices where linux.driver is ctc.

Key (type)	Values	Mandatory	Description
`ccwgroup.ctc.protocol` (int)	example: 0	Yes	The protocol/method used by the connection
`ccwgroup.ctc.type` (string)	example: CTC/A	Yes	The device/connection type
`ccwgroup.ctc.buffer` (int)	example: 32768	No	The maximum buffer size of the connection

The following properties describe ccwgroup devices where linux.driver is lcs.

Key (type)	Values	Mandatory	Description
`ccwgroup.lcs.portnumber` (int)	example: 0	Yes	The port on the card that is used
`ccwgroup.lcs.type` (string)	example: OSA LCS card	Yes	The type of the card
`ccwgroup.lcs.lancmd_timeout` (int)	example: 5	Yes	The timeout value for LAN commands in seconds

The following properties describe ccwgroup devices where linux.driver is claw.

Key (type)	Values	Mandatory	Description
`ccwgroup.claw.api_type` (string)		Yes	Determines the packing algorithm for outgoing pakets (matching the remote peer)
	IP		Using the IP protocol
	PACKED		Using an enhanced packing algorithm
	TCPIP		Using the TCP/IP protocol
`ccwgroup.claw.adapter_name` (string)	example: RS1	Yes	The host name of the remote communication peer.
`ccwgroup.claw.host_name` (string)	example: LNX1	Yes	The host name of the local adapter.
`ccwgroup.claw.read_buffer` (int)	example: 4	Yes	The number of read buffers allocated
`ccwgroup.claw.write_buffer` (int)	example: 5	Yes	The number of write buffers allocated

iucv namespace

Device objects with info.subsystem set to iucv are using the "Intra-User Comminication Vehicle" and are described by the following properties.

Key (type)	Values	Mandatory	Description
`iucv.bus_id` (string)	example: netiucv0	Yes	The device's bus id in sysfs

The following properties describe iucv devices where linux.driver is netiucv.

Key (type)	Values	Mandatory	Description
`iucv.netiucv.user` (string)	example: linux12	Yes	The guest name of the connection's target
`iucv.netiucv.buffer` (int)	example: 32768	Yes	The maximum buffer size of the connection

block namespace

Device objects representing addressable block devices, such as drives and partitions, will have info.subsystem set to block and will export a number of properties in the block namespace.

Key (type)	Values	Mandatory	Description
`block.device` (string)	example: /dev/sda	Yes	Special device file to interact with the block device
`block.major` (int)	example: 8	Yes	Major number of special file to interact with the device
`block.minor` (int)	example: 1	Yes	Minor number of special file to interact with the device
`block.is_volume` (bool)		Yes	True only when the block device is a volume that can be mounted into the file system. In this case the `volume` capability will be set and thus, properties, in the `volume` namespace are available.
`block.no_partitions` (bool)		Yes	For toplevel block devices, this is TRUE only when no known partition tables have been found on the media (In this case, if the storage device contain a file system it will be accessible using the same special device file as the one for this device object and the device object representing the filesystem will appear as a separate device object as a child). For the child, that is when `block.is_volume` is true, this property is TRUE exactly when it was created for a storage device with the `storage.no_partitions_hint` set to TRUE.
`block.have_scanned` (bool)		Yes	An internal property used by HAL to specify whether a top level block device have already been scanned for filesystems.

xen namespace

Device objects representing virtual devices under the Xen Virtual Machine Monitor, such as frontend network or block devices, will have info.subsystem set to block and will export a number of properties in then xen namespace.

Key (type)	Values	Mandatory	Description
`xen.bus_id` (string)	example: vif-0	Yes	The XenBus ID of the device
`xen.path` (string)	example: device/vif/0	Yes	The XenBus path of the device
`xen.type` (string)	example: vif	Yes	The type of Xen device

bluetooth_hci namespace

Device objects representing a Bluetooth Host Controller Interface.

Key (type)	Values	Mandatory	Description
`bluetooth_hci.address` (uint64)		Yes	Address of the host controller interface.
`bluetooth_hci.originating_device` (string)		Yes	The UDI of the physical device (e.g. an USB interface) that provides the HCI hardware.

bluetooth_acl namespace

Device objects representing Asynchronous Connection-oriented Links.

Key (type)	Values	Mandatory	Description
`bluetooth_acl.address` (uint64)		Yes	Address of the device at the other end of the connection.
`bluetooth_acl.originating_device` (string)		Yes	The UDI of the Bluetooth HCI (of capability `bluetooth_hci`) that the connection is made through.

bluetooth_sco namespace

Device objects representing Synchronous Connection-Oriented links.

Key (type)	Values	Mandatory	Description
`bluetooth_sco.address` (uint64)		Yes	Address of the device at the other end of the connection.
`bluetooth_sco.originating_device` (string)		Yes	The UDI of the Bluetooth HCI (of capability `bluetooth_hci`) that the connection is made through.

drm namespace

The drm namespace is present for Direct Rendering Manager device objects. They represent a Direct Rendering Interface.

Key (type)	Values	Mandatory	Description
`drm.dri_library` (string)		Yes	Name of the dri (Direct Rendering Interface) library (e.g. i915).
`drm.version` (string)		Yes	The drm version (of the kernel module/diver).

ps3_system_bus namespace

Devices on the PlayStation 3 system bus are represented by device objects where info.subsystem equals ps3_system_bus. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`ps3_system_bus.id` (string)	example: serial	Yes	Device identification

virtio namespace

Devices on the VirtIO bus are represented by device objects where info.subsystem equals virtio. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`virtio.id` (string)	example: serial	Yes	Device identification

virtio namespace

Devices on the IBM pSeries/iSeries 'vio' bus are represented by device objects where info.subsystem equals vio. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`vio.id` (string)	example: 1,10,3d	Yes	Device identification
`vio.type` (string)	example: viodasd, v-scsi, l-lan	Yes	Device type.

vmbus namespace

Virtual devices of the VMBus, which is part of the Hyper-V technologies (which is a hypervisor based virtualization solution) included in the Windows Server 2008, are represented by device objects where info.subsystem equals vmbus. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`vmbus.bus_id` (string)		Yes	ID of the bus.
`vmbus.device_id` (string)		Yes	ID of the device.
`vmbus.class_id` (string)	example: {f8615163-df3e-46c5-913ff2d2f965ed0e}	Yes	Class identifier of the device.

Functional Properties

The section describe functional properties of device objects, that is, properties that are merged onto device objects representing addressable hardware. In most circumstances such properties stem from a kernel level driver attached to the device represented by the device object, however, as HAL can merge properties from anywhere, they may have been merged from device information files or callouts.

system namespace

This namespace is found on the toplevel "Computer" device, and represents information about the system and the currently running kernel.

Key (type)	Values	Mandatory	Description
`system.kernel.name` (string)	example: Linux	No	The name of the kernel, usually the equivalent of `uname -s`.
`system.kernel.version` (string)	example: 2.6.5-7.104-default	No	The version of the currently running kernel. Usually the equivalent of `uname -r`.
`system.kernel.machine` (string)	example: i686	No	The "machine hardware name" of the currently running kernel. Usually the equivalent of `uname -m`.
`system.formfactor` (string)	example: laptop, desktop, server, unknown	Yes	The formfactor of the system. Usually the equivalent of `system.chassis.type` or set from information about ACPI/APM/PMU properties.
`system.hardware.vendor` (string)		No	The name of the manufacturer of the machine.
`system.product` (string)		No	The product name of the machine.
`system.hardware.version` (string)		No	The version of the machine.
`system.hardware.serial` (string)		No	The serial number of the machine.
`system.hardware.uuid` (string)		No	The unique ID of the machine.
`system.hardware.primary_video.vendor` (int)		No	The PCI vendor ID of the primary graphics card in the system.
`system.hardware.primary_video.product` (int)		No	The PCI device ID of the primary graphics card in the system.
`system.firmware.vendor` (string)		No	The firmware vendor.
`system.firmware.version` (string)		No	The firmware version.
`system.firmware.release_date` (string)		No	The release date of the firmware.
`system.chassis.manufacturer` (string)		No	The manufacturer of the chassis.
`system.chassis.type` (string)		No	The chassis type of the machine.

volume namespace

This namespace is for device objects that represent storage devices with a filesystem that can be mounted. Such device objects will have the capability volume and they will export the properties below. Note that device objects can only have the volume capability if they already have the capability block and the property block.is_volume set to TRUE.

Key (type)	Values	Mandatory	Description
`volume.ignore` (bool)		Yes	This is a hint to software higher in the stack that this volume should be ignored. If TRUE, the volume should be invisible in the UI and mount wrappers should refuse to mount it on behalf on an unprivileged user. This is useful for hiding e.g. firmware partitions (e.g. bootstrap on Mac's) and OS reinstall partitions on e.g. OEM systems.
`volume.is_mounted` (bool)		Yes	This property is TRUE if and only if the volume is mounted
`volume.is_mounted_read_only` (bool)		Yes	This property is TRUE if and only if the volume is mounted and the volume's file-system is read-only.
`volume.mount_point` (string)	example: /media/compact_flash1	Yes (is blank only when volume.is_mounted is FALSE)	A fully qualified path to the mount point of the volume
`volume.fsusage` (string)	example: filesystem	Yes	This property specifies the expected usage of the volume
	filesystem		The volume is a mountable filesystem
	partitiontable		The volume contains a partitiontable.
	raid		The volume is a member of a raid set and not mountable
	other		The volume is not mountable like a swap partition
	unused		The volume is marked a unused or free
`volume.fstype` (string)	examples: ext3, vfat	Yes (is blank if the type is unknown)	The specific type of either the file system or what the volume is used for, cf. volume.fsusage
`volume.fsversion` (string)	example: FAT32		Version number or subtype of the filesystem
`volume.label` (string)	example: 'Fedora Core 1.90'	Yes (is blank if no label is found)	The label of the volume
`volume.uuid` (string)	example: 4060-6C11	Yes (is blank if no UUID is found)	The Universal Unique Identifer for the volume
`volume.is_disc` (bool)		Yes	If the volume stems from an optical disc, this property is true and the device object will also have the capability `volume.disc`
`volume.block_size` (string)		No	The block size of the volume
`volume.num_blocks` (string)		No	Number of blocks on the volume
`volume.size` (uint64)		No	Size of the volume in bytes
`volume.is_partition` (bool)		Yes	If the volume stems from a partition on e.g. a hard disk, this property is set to `TRUE`.
`volume.linux.is_device_mapper` (bool)		Yes, but only on Linux	If the volume stems from the Linux Device Mapper this property is set to `TRUE`.
`volume.partition.number` (int)		If, and only if, `volume.is_partition` is set to `TRUE`.	The number of the partition.
`volume.partition.label` (string)		If, and only if, `volume.is_partition` is set to `TRUE`.	Label of partition. Only available for "apm" and "gpt" partition tables. Note that this is not the same as the file system label defined in `volume.label`.
`volume.partition.uuid` (string)		If, and only if, `volume.is_partition` is set to `TRUE`.	The UUID or GUID of the partition table entry. Only available for "gpt" partition tables.
`volume.partition.scheme` (string)		If, and only if, `volume.is_partition` is set to `TRUE`.	The scheme of the partition table this entry is part of. Note that this is not necessarily the same as `storage.partitioning_scheme` as some partition tables can embed other partition tables.
	mbr		Master Boot Record
	embr		Extended Master Boot Record
	gpt		GUID Partition Table as defined by EFI
	apm		Apple Partition Map
`volume.partition.type` (string)		If, and only if, `volume.is_partition` is set to `TRUE`.	The type of the partition table entry. Depends on `volume.partition.scheme`.
	`mbr` and `embr` entries		The hexadecimal encoding of the 8-bit partition type, see http://www.win.tue.nl/~aeb/partitions/partition_types-1.html for a list. For example the Linux partition type is represented as the string "0x83".
	`gpt` entries		The GUID encoded as a string. See http://en.wikipedia.org/wiki/GUID_Partition_Table for a list of well-known GUID's.
	`apm` entries		Defined in http://developer.apple.com/documentation/mac/Devices/Devices-126.html. Also note that for FAT file systems, it appears that "DOS_FAT_32", "DOS_FAT_16" and "DOS_FAT_12" are also recognized under Mac OS X (I've tested this too) cf. http://lists.apple.com/archives/Darwin-drivers/2003/May/msg00021.html
`volume.partition.flags` (strlist)		If, and only if, `volume.is_partition` is set to `TRUE`.	Flags conveying specific information about the partition entry. Dependent on the partitioning scheme.
	`mbr` and `embr` entries		Only one flag, "boot", is defined. This is used by some BIOS'es and boot loaders to populate a boot menu. It means that a partition is bootable.
	`gpt` entries		Only the flag "required" is recognized. This corresponds to bit 0 of the attibutes (at offset 48), meaning "Required for the platform to function. The system cannot function normally if this partition is removed. This partition should be considered as part of the hardware of the system, and if it is removed the system may not boot. It may contain diagnostics, recovery tools, or other code or data that is critical to the functioning of a system independent of any OS."
	`apm` entries		The following flags are recognized: "allocated" if the partition is already allocated; and "in_use" if the partition is in use; may be cleared after a system reset; and "boot" if partition contains valid boot information; and "allow_read" if partition allows reading; and "allow_write"; if partition allows writing; and "boot_code_is_pic"; if boot code is position independent
`volume.partition.media_size` (uint64)	example: 500107862016	If, and only if, `volume.is_partition` is set to `TRUE`.	If available, size of the current media or the fixed disk in the storage device.
`volume.partition.start` (uint64)	example: 32256	If, and only if, `volume.is_partition` is set to `TRUE`.	If available, the offset where the partition starts on the media or the fixed disk in the storage device.

Device objects with this capability may emit the following device conditions

Condition Name	Parameters	Example	Description
`VolumeMount`	`block.device` (string), `volume.mount_point` (string)	`/dev/sda1`, `/media/compact_flash`	Emitted when a volume is mounted
`VolumeUnmount`	`block.device` (string), `volume.mount_point` (string)	`/dev/sda1`, `/media/compact_flash`	Emitted when a volume is unmounted
`VolumeUnmountForced`	`block.device` (string), `volume.mount_point` (string)	`/dev/sda1`, `/media/compact_flash`	Emitted when a volume is forcibly unmounted because the media backing the volume was removed.

volume.disc namespace

This namespace is for device objects that represent optical discs, e.g. device objects with the capability volume.disc. Such device objects will also have the capability volume.

Key (type)	Values	Mandatory	Description
`volume.disc.has_audio` (bool)		Yes	Is true only if the disc contains audio
`volume.disc.has_data` (bool)		Yes	Is true only if the disc contains data
`volume.disc.is_vcd` (bool)		Yes	Is true only if the disc is a Video CD
`volume.disc.is_svcd` (bool)		Yes	Is true only if the disc is a Super Video CD
`volume.disc.is_videodvd` (bool)		Yes	Is true only if the disc is a Video DVD
`volume.disc.is_appendable` (bool)		Yes	Is true only if it's possible to write additional data
`volume.disc.is_blank` (bool)		Yes	Is true only if the disc is blank
`volume.disc.is_rewritable` (bool)		Yes	Is true only if the disc is rewritable
`volume.disc.capacity` (uint64)		No	Capacity of disc, in bytes
`volume.disc.type` (string)		Yes	This property specifies the physical type of the disc
	cd_rom		CD-ROM disc
	cd_r		CD-R disc
	cd_rw		CD-RW disc
	dvd_rom		DVD-ROM disc
	dvd_ram		DVD-RAM disc
	dvd_r		DVD-R disc
	dvd_rw		DVD-RW disc
	dvd_plus_r		DVD+R disc
	dvd_plus_rw		DVD+RW disc
	bd_rom		BD-ROM disc
	bd_r		BD-R disc
	bd_re		BD-RE disc
	hddvd_rom		HD DVD-ROM disc
	hddvd_r		HD DVD-R disc
	hddvd_rw		HD DVD-Rewritable disc
	unknown		Unknown type or lack of support from drive to determine the type

storage namespace

This namespace is used to describe storage devices and their capabilities. Such device objects will have the capability storage and they will export the properties below. Note that device objects can only have the storage capability if they already got capability block and the property block.is_volume set to FALSE. One significant between the storage and block namespace is that the properties exported in the storage represents constant vital product information, whereas the properties in the block namespace represent variable system-dependent information.

Key (type)	Values	Mandatory	Description
`storage.bus` (string)		Yes	Interface the storage device is attached to
	ide		IDE or ATA interface
	usb		USB interface
	ieee1394		IEEE 1394 interface
	scsi		SCSI interface
	sata		SATA interface
	pcmcia		PCMCIA interface
	mmc		MultiMediaCard (MMC) interface
	ccw		IBM s390/s390x ccw interface
	vio		IBM pSeries/iSeries Vio interface
	platform		Legacy device that is part of the platform
	linux_raid		Linux MD (multi disk) RAID device

`storage.drive_type` (string)		Yes	The type of the drive. Note that it may not be possible to probe for some of these properties so in some cases memory card readers may appear as harddisks. Device information files can be used to override this value.
	disk		The device is a harddisk
	cdrom		The device is an optical drive. The device object will also have the capability `storage.cdrom` in this case.
	floppy		The device is a floppy disk drive
	tape		The device is a tape drive
	compact_flash		The device is a card reader for Compact Flash memory cards
	memory_stick		The device is a card reader for MemoryStick memory cards
	smart_media		The device is a card reader for SmartMedia memory cards
	sd_mmc		The device is a card reader for SecureDigital/MultiMediaCard memory cards

`storage.removable` (bool)		Yes	Media can be removed from the storage device
`storage.removable.media_available` (bool)		Yes	true, if and only if, media have been detected in storage device
`storage.removable.media_size` (uint64)		Yes	Size of media in storage device. Available only if media have been detected in storage device.
`storage.removable.support_async_notification` (bool)		Yes	Whether the drive reports asynchronous notification for media change.
`storage.partitioning_scheme` (string)		Only when media is inserted and is partitioned	The partitioning scheme of the media.
	mbr		Master Boot Record partitioning scheme used in most PC's
	gpt		GUID Partitioning Table as defined by UEFI
	apm		Apple Partition Map, used in non-Intel Apple computers
`storage.size` (uint64)		No	size in bytes of the storage device - only meaningful if storage.removable is FALSE
`storage.requires_eject` (bool)		Yes	The eject ioctl is required to properly eject the media
`storage.hotpluggable` (bool)		Yes	The storage device can be removed while the system is running
`storage.media_check_enabled` (bool)		Yes	If this property is set to FALSE then HAL will not continuosly poll for media changes.
`storage.automount_enabled_hint` (bool)		Yes	This property is a hint to desktop file managers that they shouldn't automount volumes of the storage device when they appear.
`storage.no_partitions_hint` (bool)		Yes	This property is a hint to programs that maintain the `/etc/fstab` file to signal, when TRUE, that the storage drive (such as floppy or optical drives) is used for media with no partition table so an entry can be added ahead of media insertion time. Note that this is only a hint; media may be inserted that has partition tables that the kernel may respect. Conversely, when this is FALSE media without partition tables may be inserted (an example is a Compact Flash card; this media is normally formatted with a PC style partition table and a single FAT partition. However, it may be formatted with just a single FAT partition and no partition table).
`storage.originating_device` (string)		Yes	This contains the UDI of the device object representing the device or blank if there is no such device.
`storage.model` (string)		Yes	The name of the drive
`storage.vendor` (string)		Yes	The vendor of the drive
`storage.serial` (string)		No	The serial number of the drive
`storage.firmware_revision` (string)		No	The revision of the firmware of the drive
`storage.icon.drive` (string)		No	Name of icon to use for displaying the drive. The name must comply with freedesktop.org icon-theme specification and must not be an absolute path. This property exists such that e.g. OEM's can install icons in `/usr/share/icons/hicolor` a device information file matching their device.
`storage.icon.volume` (string)		No	Name of icon to use for displaying volumes from the drive. The name must comply with freedesktop.org icon-theme specification and must not be an absolute path. This property exists such that e.g. OEM's can install icons in `/usr/share/icons/hicolor` a device information file matching their device.

storage.cdrom namespace

This namespace is used to describe optical storage drives and their capabilities.Such device objects will have the capability storage.cdrom and they will export the properties below. Note that device objects can only have the storage.cdrom capability if they already got the capability storage.

Key (type)	Mandatory	Description
`storage.cdrom.cdr` (bool)	Yes	TRUE when the optical drive can write CD-R discs
`storage.cdrom.cdrw` (bool)	Yes	TRUE when the optical drive can blank and write to CD-RW discs
`storage.cdrom.dvd` (bool)	Yes	TRUE when the optical drive can read DVD-ROM discs
`storage.cdrom.dvdr` (bool)	Yes	TRUE when the optical drive can write to DVD-R discs
`storage.cdrom.dvdrw` (bool)	Yes	TRUE when the optical drive can blank and write to DVD-RW discs
`storage.cdrom.dvdram` (bool)	Yes	TRUE when the optical drive can write to DVD-RAM discs
`storage.cdrom.dvdplusr` (bool)	Yes	TRUE when the optical drive can write to DVD+R discs
`storage.cdrom.dvdplusrw` (bool)	Yes	TRUE when the optical drive can blank and write to DVD+RW discs
`storage.cdrom.dvdplusrwdl` (bool)	Yes	TRUE when the optical drive can blank and write to DVD+RW Dual-Layer discs
`storage.cdrom.dvdplusrdl` (bool)	Yes	TRUE when the optical drive can write to DVD+R Dual-Layer discs
`storage.cdrom.bd` (bool)	Yes	TRUE when the optical drive can read Blu-ray ROM discs
`storage.cdrom.bdr` (bool)	Yes	TRUE when the optical drive can write to Blu-ray Recordable discs
`storage.cdrom.bdre` (bool)	Yes	TRUE when the optical drive can write to Blu-ray Rewritable discs
`storage.cdrom.hddvd` (bool)	Yes	TRUE when the optical drive can read Read-only HD DVD discs
`storage.cdrom.hddvdr` (bool)	Yes	TRUE when the optical drive can write to Write-once HD DVD discs
`storage.cdrom.hddvdrw` (bool)	Yes	TRUE when the optical drive can write to Rewritable HD DVD discs
`storage.cdrom.mrw` (bool)	Yes	TRUE when the optical drive can read MRW (Mount Rainier Rewrite) discs
`storage.cdrom.mrw_w` (bool)	Yes	TRUE when the optical drive can write MRW (Mount Rainier Rewrite) discs
`storage.cdrom.mo` (bool)	No	TRUE when the optical drive is a MO (Magneto Optical) device.
`storage.cdrom.support_multisession` (bool)	Yes	TRUE if the drive can read multisession discs
`storage.cdrom.support_media_changed` (bool)	Yes	TRUE if the drive can generate media changed events
`storage.cdrom.read_speed` (int)	Yes	The maximum reading speed, in kb/s
`storage.cdrom.write_speed` (int)	Yes	The maximum writing speed, in kb/s
`storage.cdrom.write_speeds` (strlist)	No	By the device supported write speeds in kb/s

storage.linux_raid namespace

This namespace is used to describe logical Software RAID devices under Linux using the md driver. By and large, all the same properties under the storage name space applies except that storage.serial is set to the UUID of the RAID set, storage.firmware_version is set to the version of the md driver and the value of storage.hotpluggable is taken from the enclosing drive of the first RAID component encountered. In addition, the following properties are available.

Key (type)	Mandatory	Description
`storage.linux_raid.level` (string)	Yes	the RAID level of the device as reported by the kernel (linear, raid0, raid1, raid4, raid5, raid6, raid10)
`storage.linux_raid.sysfs_path` (string)	Yes	sysfs path of device, e.g. /sys/block/md0
`storage.linux_raid.num_components` (int)	Yes	Number of components in the RAID array
`storage.linux_raid.num_components_active` (int)	Yes	Number of active components in the RAID array. If less than `storage.linux_raid.num_components` it means that the RAID array is running in degraded mode.
`storage.linux_raid.components` (strlist)	Yes	UDI's of the volumes constituting the array.
`storage.linux_raid.is_syncing` (bool)	Yes	TRUE if, and only if, the array is currently syncing
`storage.linux_raid.sync.action` (string)	only if `.is_syncing` is TRUE	The syncing mechanism as reported by the kernel (idle, resync, check, repair, recover)
`storage.linux_raid.sync.progress` (double)	only if `.is_syncing` is TRUE	Number between 0 and 1 representing progress of the sync operation. This is updated regulary when syncing is happening.
`storage.linux_raid.sync.speed` (uint64)	only if `.is_syncing` is TRUE	Speed of the sync operation, in kB/s. This is updated regulary when syncing is happening.

net namespace

This namespace is used to describe networking devices and their capabilities.Such device objects will have the capability net and they will export the properties below. This namespace only describe the generic aspect of networking devices; specific networking technologies such as IEEE 802.3, IEEE 802.11 and Bluetooth have separate namespaces.

Key (type)	Values	Mandatory	Description
`net.address` (string)		Yes	Hardware address as a string. Is hardware dependant
`net.arp_proto_hw_id` (string)		Yes	ARP protocol hardware identifier
`net.interface` (string)		Yes	Name of the interface; may change if an interface is renamed
`net.interface_up` (bool)		No	Whether the interface is up
`net.linux.ifindex` (string)		Yes (only on Linux)	Index of the interface
`net.originating_device` (string)		Yes	UDI of the device the network device is bound to.
`net.media` (string)	example: Ethernet	Yes	Textual description of the networking media

net.80203 namespace

Ethernet networking devices is described in this namespace for device objects with the capability net.80203. Note that device objects can only have the net.80203 capability if they already have the capability net.

Key (type)	Values	Mandatory	Description
`net.80203.link` (bool)		Only if the `net.80203` capability is set and `net.interface_up` is `TRUE`.	True if the ethernet adaptor is connected to a another transceiver. NOTE: property not implemented yet.
`net.80203.rate` (uint64)	example: 100000000	Only if the `net.80203` capability is set and `net.80203.link` is `TRUE`.	Bandwidth of connection, in bits/s. NOTE: property not implemented yet.
`net.80203.mac_address` (uint64)	example: 0x0010605d8ef4	Only if the `net.80203` is set	48-bit address

net.80211 namespace

Wireless ethernet networking devices is described in this namespace for device objects with the capability net.80211. Note that device objects can only have the net.80211 capability if they already have the capability net.

Key (type)	Values	Mandatory	Description
`net.80211.mac_address` (uint64)	example: 0x0010605d8ef4	Only if the `net.80211` capability is set	48-bit address

net.bridge namespace

Bridge ethernet networking devices is described in this namespace for device objects with the capability net.bridge. Note that device objects can only have the net.bridge capability if they already have the capability net.

Key (type)	Values	Mandatory	Description
`net.bridge.mac_address` (uint64)	example: 0x0010605d8ef4	Only if the `net.bridge` capability is set	48-bit address

net.bluetooth namespace

Bluetooth ethernet networking devices is described in this namespace for device objects with the capability net.bluetooth. Note that device objects can only have the net.bluetooth capability if they already have the capability net.

Key (type)	Values	Mandatory	Description
`net.bluetooth.mac_address` (uint64)	example: 0x0010605d8ef4	Only if the `net.bluetooth` capability is set	48-bit address
`net.bluetooth.name` (string)	example: Network Access Point Service	Only if the `net.bluetooth` capability is set and Bluez is being used.	Displayable Name for network connection
`net.bluetooth.uuid` (string)	example: 00001116-0000-1000-8000-00805f9b34fb	Only if the `net.bluetooth` capability is set and Bluez is being used.	Universal Unique Identifier for network connection

net.irda namespace

IrDA (Infrared Data Association) Networking devices are described in this namespace for device objects with the capability net.irda. Note that device objects can only have the net.irda capability if they already have the capability net.

net.80211control namespace

Control devices for Wireless ethernet networking devices are described in this namespace for device objects with the capability net.80211control. Note that device objects can only have the net.80211control capability if they already have the capability net. Warning: You should know what you do if you touch this devices. They are not always stable and can cause (kernel) crashes (on linux).

input namespace

This namespace is concerned with human input devices such as keyboards, mice, pointing devices and game controllers. If a device object has the capability input then the following properties are available

Key (type)	Values	Mandatory	Description
`input.device` (string)		Yes	Special device file for recieving input events
`input.x11_driver` (string)	e.g. "evdev"	No	X11 input driver to use

input.keys namespace

The input device have keys that can be pressed. No namespace specific properties.

input.keypad namespace

The input device have keypad keys. No namespace specific properties.

input.keyboard namespace

The input device is a normal keyboard. No namespace specific properties.

input.mouse namespace

The input device is a mouse. No namespace specific properties.

input.switch namespace

The input device is a switch, e.g. it has buttons with state. No namespace specific properties.

input.joystick namespace

The input device is a joystick. No namespace specific properties.

input.tablet namespace

The input device is a tablet. No namespace specific properties.

input.keymap namespace

Device objects with the capability input.keymap provide facilities to remap keyboard buttons.

Key (type)	Values	Mandatory	Description
`input.keymap.data` (strlist)	e.g. "e017:brightnessup"	No	The scancode is represented in hex and the keycode name as as string. The keycode name is not case sensitive. On Linux, the keycode name should be the same constant as present in /usr/include/linux/input.h with the 'KEY_' prefix removed, e.g. 'KEY_SLEEP' -> 'sleep'. You can append as many `input.keymap.data` values as there are keys to remap.

input.xkb namespace

Device objects with the capability input.keys can provide information about their physical layout.

Key (type)	Values	Mandatory	Description
`input.xkb.rules` (string)	e.g. "base"	Yes	XKB rules file to use; 'base' is standard, but 'xorg' or 'xfree86' may be needed for backwards compatibility with very old versions of XKB data.
`input.xkb.model` (string)	e.g. "logicdp"	Yes	Physical keyboard model (e.g. Logitech Cordless Freedom Pro), as given to XKB.
`input.xkb.layout` (string)	e.g. "us"	Yes	Keyboard layout (as engraved on the keys).
`input.xkb.variant` (string)	e.g. "nodeadkeys"	No	Variant of the XKB layout (if any) to use.
`input.xkb.options` (strlist)	e.g. "ctrl:nocaps"	No	Options to be provided to XKB.

pcmcia_socket namespace

Device objects with the capability pcmcia_socket represent bridge devices (the actual bus of the device may differ) that PCMCIA cards can be attached to. The following properties are available.

Key (type)	Values	Mandatory	Description
`pcmcia_socket.number` (int)		Yes	PCMCIA socket number, starting from zero

printer namespace

Device objects with the capability printer represent printers. The following properties are available.

Key (type)	Mandatory	Description
`printer.device` (string)	Yes	TODO
`printer.vendor` (string)	Yes	TODO
`printer.product` (string)	Yes	TODO
`printer.serial` (string)	Yes	TODO
`printer.description` (string)	Yes	TODO
`printer.commandset` (strlist)	No	List of supported commands / printer languages.

portable_audio_player namespace

Device objects with the capability portable_audio_player represent portable audio players that can be attached to a computer to exchange files. They can also playback audio. Sometimes they can also record audio. This capability can't, in general, be reliably probed from the hardware so the information needs to be merged from either device information files or callouts. Therefore this capability should be merged on the appropriate device object that represents the addressable piece of hardware that is the portable music player; for USB devices this would be the device object representing the appropriate USB interface. The following properties are available:

Key (type)	Values	Mandatory	Description
`portable_audio_player.access_method.protocols` (strlist)	example: storage ipod mtp pde iriver karma	Yes	Indicates transfer protocols that this device can speak. `storage` indicates USB Mass Storage (UMS) is an access protocol. `ipod` indicates UMS plus an iTunes-style database. `mtp` indicates a device using Microsoft's Media Transfer Protocol. Arbitrary values for newer or obscure protocols are allowed but entities providing this information should try to ensure that they are not duplicating protocols under a different name.
`portable_audio_player.access_method.drivers` (strlist)	example: libgpod, libmtp, libnjb, libifp, libkarma	No	Indicates installed device driver libraries that can handle this device. These drivers can export information in `portable_audio_player.[drivername]` sub-namespaces. Can also be used by libraries or programs providing extra device information to indicate the presence of this information in the appropriate sub-namespace.
`portable_audio_player.[drivername].protocol` (strlist)	example: mtp	If portable_audio_player.drivers is set	This entry is required for drivers listed in `portable_audio_player.access_method.drivers`. Indicates which protocol in `portable_audio_player.access_method.protocols` a particular driver will use. If the driver is providing information only, this should be set to `information`.
`portable_audio_player.output_formats` (strlist)	example: audio/mpeg audio/x-ms-wma	Yes	A string list of MIME-types representing the kind of audio formats that the device can play back.
`portable_audio_player.input_formats` (strlist)	example: audio/x-wav	Yes	A string list of MIME-types representing the kind of audio formats that the device can record. If empty, it means that the device is not capable of recording.
`portable_audio_player.folder_depth` (int)	example: 1 (If the device only supports one sub-folder)	No	If portable_audio_player.access_method.protocols contains "storage", this tells applications exactly how deep of directory hierarchies files should be placed in. If all files are put in a sub-folder (with the audio_folders property), only the depth within that sub-folder should be entered here. If the device does not have a limit, do not set this property.
`portable_audio_player.audio_folders` (strlist)	example: music/ voice/ linein/	No	If portable_audio_player.access_method.protocols contains "storage", this may contain a string list of folders in which music can be found. Paths are relative to the mount point of the device. If there is one or more entry in this property, the first one is where files will be written to by applications. Do not enter a folder and a parent of that folder. If the device places files in its root directory, then do not set this property.
`portable_audio_player.playlist_format` (strlist)	example: audio/x-mpegurl audio/x-somethingelse	No	A string list of the MIME-type of the playlist formats accepted by this device. Leave blank if none.
`portable_audio_player.playlist_path` (string)	examples: playlists/%File or Playlist.m3u	No	Set to the path to which playlists should be written. Leave blank if playlist files are not supported. If the device supports a single playlist with a specific name/path, set this to the path relative to the mount point that it should be saved to. If it supports multiple playlists, use the %File variable as needed. Applications are responsible for substituting %File with the desired playlist file name, noting that it's use in this string is optional.
`portable_audio_player.storage_device` (string)	examples: a udi	No	Set to the udi of the portable_audio_player device if portable_audio_player.access_method.protocols contains storage for a USB Mass Storage (UMS) music player. Mandatory for storage.

alsa namespace

Device objects with the capability alsa represent all the streams available through ALSA on a soundcard.

Key (type)	Values	Mandatory	Description
`alsa.card` (int)		Yes	Card number in system as registered by ALSA.
`alsa.card_id` (string)	Examples: `I82801DBICH4`, `MP3`	No	Textual description of the card.
`alsa.device` (int)		Yes	Device number assigned by ALSA for a current card.
`alsa.device_file` (string)		Yes	The device node to access the ALSA device.
`alsa.device_id` (string)	Examples: `Intel 82801DB-ICH4 MIC2 ADC`	No	Textual description of the specific device for a card
`alsa.pcm_class` (string)		No	The PCM class of the device.
	generic		A standard PCM sound device (SND_PCM_CLASS_GENERIC).
	multi		A multichannel device PCM sound device (SND_PCM_CLASS_MULTI) which e.g. contains a generic and a modem device.
	digitizer		A PCM digitizer device (SND_PCM_CLASS_DIGITIZER).
	modem		A PCM modem device (SND_PCM_CLASS_MODEM).
	unknown		The value is 'unknown' if the kernel provide no information about the PCM device class of the device (e.g. the file pcm_class is missing).
	none		The value is 'none' if this there is no PCM class for this device.
`alsa.originating_device` (string)		Yes	UDI of the device the ALSA device is bound to.
`alsa.type` (string)		Yes	The type of the stream.
	`control`		Stream is control device.
	`capture`		Stream is capture device.
	`midi`		Stream is MIDI device.
	`playback`		Stream is playback device.
	`unknown`		The type of the device is unknown.
	`hw_specific`		This is a hardware specific device (as e.g. from snd_fm801 for Fortemedia FM801 PCI Audio). The driver can use it freely for purposes that are not covered by standard ALSA API.
	`timer`		Stream is the global ALSA timer device. This means, the device is for all ALSA devices/cards.
	`sequencer`		Stream is the global ALSA sequencer device. This means, the device is for all ALSA devices/cards.
	`unknown`		Stream is unknown device.

oss namespace

Device objects with the capability oss represent all the streams available through OSS on a soundcard. OSS devices could be emulated by ALSA.

Key (type)	Values	Mandatory	Description
`oss.card` (int)		Yes	Card number in system as registered by OSS (and/or ALSA).
`oss.card_id` (string)	Examples: `I82801DBICH4`, `MP3`	No	Textual description of the card.
`oss.device` (int)		Yes	Device number assigned by OSS/ALSA for a current card.
`oss.device_file` (string)		Yes	The device node to access the OSS device.
`oss.device_id` (string)	Examples: `Intel 82801DB-ICH4 MIC2 ADC`	No	Textual description of the specific device for a card
`oss.originating_device` (string)		Yes	UDI of the device the OSS device is bound to.
`oss.type` (string)		Yes	The type of the stream.
	`mixer`		Stream is control/mixer device.
	`pcm`		Stream is PCM device.
	`midi`		Stream is MIDI device.
	`sequencer`		Stream is a global OSS sequencer device. This means, the device is for all OSS devices/cards.
	`unknown`		Stream is unknown device.

camera namespace

Device objects with the capability camera represent digital still cameras that can be attached to a computer to exchange files. This does not include card readers for memory cards used for cameras. This capability can't, in general, be reliably probed from the hardware so the information needs to be merged from either device information files or callouts. Therefore this capability should be merged on the appropriate device object that represents the addressable piece of hardware that is the digital still camera; for USB devices this would be the device object representing the appropriate USB interface. The following properties are available:

Key (type)	Values	Mandatory	Description
`camera.access_method` (string)		Yes	This property defines how the device is accessed
	storage		The device is accessed as a Mass Storage device through a kernel driver. Application Developers should descent down the device object tree to find the device object of capability `storage` in order to access the device.
	user		The device is accessed from userspace through a userspace driver.

`camera.libgphoto2.support` (bool)		No	If true, the device is supported by a userspace driver from the libgphoto2 project.

scanner namespace

Device objects with the capability scanner represent image scanners. This capability should be merged on the appropriate device object that represents the addressable piece of hardware that is the digital still camera; for USB devices this would be the device object representing the appropriate USB interface. The following properties are available:

Key (type)	Values	Mandatory	Description
`scanner.access_method` (string)		Yes	This property defines how the device is accessed
	proprietary		The device is accessed from userspace through a userspace driver such as SANE.

laptop_panel namespace

Device objects with the capability laptop_panel represent devices capable of changing the brightness of the display.

Key (type)	Mandatory	Description
`laptop_panel.num_levels` (int)	Yes	The brightness levels supported by the adaptor.
`laptop_panel.access_method` (string)	Yes	The access method to use in scripts, e.g. pmu, toshiba, ibm, sony.
`laptop_panel.brightness_in_hardware` (bool)	No	On some laptops, the brightness control is all done in hardware but the hardware also synthesizes keypresses when the brightness is changed. If this key is set true, then any power manager software should not attempt to set any new values on brightness keypress, as it may cause the panel to flash uncontrollably.

The following methods exist on the interface org.freedesktop.Hal.Device.LaptopPanel.

Method (parameter types)	Parameters	Mandatory	Description
`SetBrightness` (integer)	The hardware brightness state, which should be between 0 and `laptop_panel.num_levels` - 1.	No	This method adjusts the brightness on an laptop screen. The values are returned as hardware values rather than percentages as we cannot easily to floating point rounding in shell code and therefore use the raw values to prevent integer rounding errors.
integer `GetBrightness` (void)	Returns the hardware brightness state, which should be between 0 and `laptop_panel.num_levels` - 1.	No	This method gets the hardware brightness of the laptop screen, which we may need to do fairly regually on hardware that changes the values in hardware without a software event.

ac_adapter namespace

Device objects with the capability ac_adapter represent all the devices capable of powering the system from AC power

Key (type)	Values	Mandatory	Description
`ac_adapter.present` (bool)		Yes	The state of the adapter, i.e. whether it is providing power to the unit from mains power.

battery namespace

Device objects with the capability battery represent all the devices having some battery (in many cases - rechargeable) inside.

Key (type)	Values	Mandatory	Description
`battery.present` (bool)		Yes	This is present as some smart batteries can have acpi/pmu entries, and be physically missing.
`battery.type` (string)		Yes	This property defines the type of the device holding the battery. This property is defined for the development simplicity - battery indicators can use it to find the proper iconic representation.
	`pda`		The device containing the battery is a personal digital assistant, e.g. a device that looks like a handheld computer to do specific tasks such as keeping notes or containing a personal database
	`ups`		A battery powered power supply that is guaranteed to provide power to a computer in the event of interruptions in the incoming electrical power. Most of the time this is an external device.
	`primary`		The battery is a primary power source for the system - an example are laptop batteries.
	`mouse`		The device containing the battery is a mouse.
	`keyboard`		The device containing the battery is a keyboard.
	`keyboard_mouse`		The device containing the battery is a combined mouse and keyboard.
	`camera`		The device containing the battery is a camera.
	`usb`		The device containing the battery is a generic usb device.
	`unknown`		The device containing the battery is not covered by other types.
`battery.charge_level.unit` (string)	Examples: `mWh`, `percent`	No	The physical unit used by the charge level properties (maximum and current). In many cases, this property is omitted - which indicates that the charge properties are measured in some unknown units. The units should never be mAh as this is not a measurement of charge.
`battery.charge_level.design` (int)		Yes	The maximum level of charge the device was designed for. Measured in `"battery.charge_level.unit"` units.
`battery.charge_level.last_full` (int)		Yes	The maximum level of charge the device could hold the last time it was full. Measured in `"battery.charge_level.unit"` units.
`battery.charge_level.current` (int)		Yes	The current level of charge which the device can is holding. Measured in `"battery.charge_level.unit"` units.
`battery.charge_level.rate` (int)		No	The discharge/charge rate measured in `"battery.charge_level.unit"` units per second.
`battery.charge_level.warning` (int)		No	Once the charge level of the battery drops below this value its state changes to 'warning'. Measured in `"battery.charge_level.unit"` units.
`battery.charge_level.low` (int)		No	Once the charge level of the battery drops below this value its state changes to 'low'. Measured in `"battery.charge_level.unit"` units.
`battery.charge_level.granularity_1` (int)		No	Granularity value one of the battery measured in `"battery.charge_level.unit"` units .
`battery.charge_level.granularity_2` (int)		No	Granularity value two of the battery measured in `"battery.charge_level.unit"` units.
`battery.reporting.unit` (string)	Examples: `mWh`, `mAh`, `percent`	No	The physical unit used by the charge level properties (maximum and current) as reported by the hardware. In many cases, this property is omitted - which indicates that the charge properties are measured in some unknown units.
`battery.reporting.design` (int)		Yes	The maximum level of charge the device was designed for, as reported by the hardware. Measured in `"battery.reporting.unit"` units.
`battery.reporting.last_full` (int)		No	The maximum level of charge the device could hold the last time it was full, as reported by the hardware. Measured in `"battery.reporting.unit"` units.
`battery.reporting.current` (int)		No	The current level of charge which the device is holding, as reported by the hardware. Measured in `"battery.reporting.unit"` units.
`battery.reporting.rate` (int)		No	The discharge/charge rate as reported by the hardware measured in `"battery.reporting.unit"` units per second.
`battery.reporting.warning` (int)		No	Once the hardware charge level of the battery drops below this value its state changes to 'warning'. Measured in `"battery.reporting.unit"` units.
`battery.reporting.low` (int)		No	Once the hardware charge level of the battery drops below this value its state changes to 'low'. Measured in `"battery.reporting.unit"` units.
`battery.reporting.granularity_1` (int)		No	Hardware granularity value one of the battery measured in `"battery.reporting.unit"` units .
`battery.reporting.granularity_2` (int)		No	Hardware granularity value two of the battery measured in `"battery.reporting.unit"` units.
`battery.charge_level.capacity_state` (string)	Examples: `ok`, `critical`	No	The capacity state of the battery.
`battery.voltage.unit` (string)	Examples: `mV`	No	The physical measurement unit used by the voltage properties (design and current).
`battery.voltage.design` (int)		Yes	The voltage level for which the battery is designed for. Measured in `"battery.voltage.unit"` units.
`battery.voltage.current` (int)		Yes	The voltage level currently emitted by the battery. Measured in `"battery.voltage.unit"` units.
`battery.alarm.unit` (string)	Examples: `mWh`, `mAh`	No	The physical measurement unit used by the alarm property.
`battery.alarm.design` (int)		No	Once the charge level of the battery drops below this value its state changes to 'alarm'. Measured in `"battery.alarm.unit"` units.
`battery.remaining_time` (int)		No	Remaining time, in seconds, that the battery can provide power (if discharging) or the time until charged (if charging). This is an estimate and may be imprecise. This key is not present for invalid data.
`battery.remaining_time.calculate_per_time` (bool)		No	If this property is `true` the `battery.remaining_time` becomes guessed from `battery.charge_level.current` and time.
`battery.charge_level.percentage` (int)		No	Charge, normalised to percent. This is useful if an application does not want to process the raw values and do all the extra checks on the result. This key is not present for invalid data.
`battery.is_rechargeable` (bool)		No	True if the battery unit is rechargeable, false if its is one-time (disposable after one usage).
`battery.rechargeable.is_charging` (bool)		Only if `battery.is_rechargeable` is TRUE	TRUE if, and only if, the battery is charging.
`battery.rechargeable.is_discharging` (bool)		Only if `battery.is_rechargeable` is TRUE	TRUE if, and only if, the battery is discharging.
`battery.command_interface` (string)		No	The abstract name allowing daemons and/or user-level apps to distinguish some groups of devices having similar programming interface. Introduced mostly for the daemons' coding simplicity.
`battery.vendor` (string)		No	Vendor of the battery.
`battery.model` (string)		No	Make of the battery.
`battery.reporting.technology` (string)	example: LION	No	The technology of the battery as reported by the hardware.
`battery.technology` (string)	lead-acid, lithium-ion, lithium-polymer, nickel-metal-hydride, unknown	No	The technology of the battery processed to a few standard types. This key is needed as the hardware often does not specify the description text for a battery, and so we have to calculate it from the output of `battery.reporting.technology`.
`battery.serial` (string)		No	A string uniquely identifying the instance of the battery; it will be different for two (otherwise) identical batteries.

button namespace

Device objects with the capability button represent the devices capable of providing a state to the system.

Key (type)	Values	Mandatory	Description
`button.type` (string)		No	The type of button
	lid		The switch on a laptop that senses whether the lid is open or closed
	power		The main power button on the computer.
	sleep		The sleep button on a computer capable of putting the computer into a suspend state
`button.has_state` (bool)		no	True if the button maintains state, e.g. can toggled on/off
`button.state.value` (bool)		Only when `button.has_state` is TRUE	State of the button, TRUE if it is enabled

Device objects with this capability may emit the following events.

Condition Name	Parameters	Example	Description
`ButtonPressed`	`button.type (string)`	sleep	Emitted when a button is pressed

processor namespace

Device objects with the capability processor represent CPU's in the system.

Key (type)	Values	Mandatory	Description
`processor.number` (int)		Yes	The internal processor number in the system, starting from zero
`processor.can_throttle` (bool)		No	Whether the processor supports throttling to decrease it's own clock speed
`processor.maximum_speed` (long)	example: 2200	No	The maximum speed of the processor in units of MHz

light_sensor namespace

Device objects with the capability sensor represent light sensors in the system.

Key (type)	Mandatory	Description
`light_sensor.sensor_locations` (strlist)	Yes	The locations of the sensors
`light_sensor.num_sensors` (int)	Yes	Number of physical sensors
`light_sensor.num_levels` (int)	Yes	The number of levels of the sensors

PDA namespace

Device objects with the capability pda represent Personal Digital Assistant (PDA) devices.

Key (type)	Values	Mandatory	Description
`pda.platform` (string)	e.g. palm or pocketpc	Yes	The type of the PDA platform
`pda.palm.hotsync_interface` (string)		Yes	Path to the Palm hotsync interface e.g. a linux device file (e.g. USB) or a serial device.
`pda.pocketpc.hotsync_interface` (string)		Yes	Path to the Pocket PC (e.g. HP iPAQ) hotsync interface e.g. a linux device file (e.g. USB) or a serial device.

power_management namespace

Keys with the prefix power_management provide information about power management supported by the system.

Key (type)	Values	Mandatory	Description
`power_management.type` (string)	Examples: `apm`, `acpi`, `pmu`	Yes	The power management subsystem used on the computer.
`power_management.can_suspend` (bool)		Yes	If suspend support is compiled into the kernel. NB. This may not mean the machine is able to suspend successfully.
`power_management.can_suspend_hybrid` (bool)		Yes	If the system is capable of hybrid suspend.
`power_management.can_hibernate` (bool)		Yes	If hibernation support is compiled into the kernel. NB. This may not mean the machine is able to hibernate successfully.
`power_management.is_powersave_set` (bool)		Yes	Is the last value passed to the SetPowerSave method.
`power_management.quirk.s3_bios` (bool)		No	Use the S3_BIOS kernel command for suspend.
`power_management.quirk.s3_mode` (bool)		No	Use the S3_MODE kernel command for suspend.
`power_management.quirk.dpms_suspend` (bool)		No	Suspend the video card via DPMS on suspend.
`power_management.quirk.vga_mode_3` (bool)		No	Reset the VGA text mode to mode 3 on resume.
`power_management.quirk.dpms_on` (bool)		No	Reactivate the screen with DPMS on resume.
`power_management.quirk.vbe_post` (bool)		No	Run the VGA BIOS Power On Self Test (POST) on resume.
`power_management.quirk.vbestate_restore` (bool)		No	Save the VGA BIOS state before suspend, and restore it on resume.
`power_management.quirk.vbemode_restore` (bool)		No	Save the VGA BIOS mode before suspend, and restore it on resume.
`power_management.quirk.radeon_off` (bool)		No	Turn off the Radeon DAC off before suspend.
`power_management.quirk.reset_brightness` (bool)		No	Reset the brightness state after resume.
`power_management.quirk.no_fb` (bool)		No	True if the machine can only suspend when not using framebuffer.
`power_management.quirk.none` (bool)		No	No quirks are necessary for suspend or resume.

tape namespace

Device objects with the capability tape represent tape devices.

Key (type)	Values	Mandatory	Description
`tape.major` (int)	example: 254	Yes	The device's major number
`tape.minor` (int)	example: 0	Yes	The device's minor number

killswitch namespace

Device objects with the capability killswitch represent switches to turn a radio on and off. See also the section called “org.freedesktop.Hal.Device.KillSwitch interface”.

Key (type)	Values	Mandatory	Description
`killswitch.type` (string)		Yes	Type of the kill switch
	wlan		Kill switch is for turning Wireless LAN (WLAN) networking on/off
	bluetooth		Kill switch is for turning Bluetooth on/off
	wwan		Kill switch is for turning Wireless WAN (WWAN) networking on/off
`killswitch.access_method` (string)		Yes	How HAL should program the switch

video4linux namespace

Device objects with the capability video4linux represent Video4Linux devices.

Key (type)	Values	Mandatory	Description
`video4linux.device` (string)	Example: /dev/video0	Yes	The device node to access the Video4Linux device.
`video4linux.version` (string)	Example: 2	Yes	The highest Video4Linux API version supported by the device.

video4linux.video_capture namespace

The video4linux device can capture video. No namespace specific properties.

video4linux.video_output namespace

The video4linux device can output video. No namespace specific properties.

video4linux.video_overlay namespace

The video4linux device can overlay video. No namespace specific properties.

video4linux.audio namespace

The video4linux device has audio inputs or outputs. No namespace specific properties.

video4linux.tuner namespace

The video4linux device has some sort of tuner or modulator to receive or emit RF-modulated video signals. No namespace specific properties.

video4linux.radio namespace

The video4linux device is a radio device. No namespace specific properties.

of_platform namespace

Devices on the virtual 'of_platform' bus are represented by device objects where info.subsystem equals of_platform. The following properties are available for such device objects.

Key (type)	Values	Mandatory	Description
`of_platform.id` (string)	example: f0003000.ethernet	Yes	Device identification

Misc. Properties

access_control namespace

Device objects with the capability access_control represent devices where access to a special device file can be granted/revoked to unprivileged users.

Key (type)	Values	Mandatory	Description
`access_control.file` (string)	Example: /dev/snd/pcmC0D1p	Yes	Name of the special device file that access can be granted to.
`access_control.type` (string)	Example: cdrom	Yes	Type of access - only makes sense when PolicyKit support is enabled; it's used by PolicyKit to compute what privilege to check for by prepending `hal-device-file-` to the value.
`access_control.grant_user` (strlist)	Example: "gdm, flumotion"	No	List of UNIX user names to always grant access to the device. This is useful for 3rd party system-wide packages that need access to a device to function properly.
`access_control.grant_group` (strlist)	Example: "pvr_software, staff"	No	List of UNIX group names to always grant access to the device. This is useful for 3rd party system-wide packages that need access to a device to function properly.

Deprecated Properties

The section represents properties that are deprecated and should be no longer used. The properties/keys will be removed, but not before the date in the following table:

Key (type)	Replacement	Remove (date)	Notes
`portable_audio_player.access_method` (string)	`portable_audio_player.access_method.[drivers, protocols]` (strlist)	2008-05-03	Original entry can only indicate UMS or userspace driver devices, while some devices can be both. New structure doesn't have this limitation.
`portable_audio_player.type` (string)	`portable_audio_player.access_method.[drivers, protocols]` (strlist)	2008-05-03	New structure allows for better definition of access protocols and handlers.
`power_management.can_suspend_to_ram` (bool)	`power_management.can_suspend`	2007-05-01
`power_management.can_suspend_to_disk` (bool)	`power_management.can_hibernate`	2007-05-01

Chapter 6. D-Bus interfaces

Table of Contents

org.freedesktop.Hal.Manager interface
org.freedesktop.Hal.Device interface
org.freedesktop.Hal.Device.SystemPowerManagement interface
org.freedesktop.Hal.Device.CPUFreq interface
org.freedesktop.Hal.Device.WakeOnLan interface
org.freedesktop.Hal.Device.DockStation interface
org.freedesktop.Hal.Device.LaptopPanel interface
org.freedesktop.Hal.Device.KeyboardBacklight interface
org.freedesktop.Hal.Device.LightSensor interface
org.freedesktop.Hal.Device.Storage interface
org.freedesktop.Hal.Device.Storage.Removable interface
org.freedesktop.Hal.Device.Volume interface
org.freedesktop.Hal.Device.Volume.Crypto interface
org.freedesktop.Hal.Device.KillSwitch interface
org.freedesktop.Hal.Device.AccessControl interface
org.freedesktop.Hal.SingletonAddon interface

All of the HAL D-Bus interfaces are introspectable using the standard D-Bus introspection methods (e.g. they all implement the org.freedesktop.DBus.Introspectable interface). For example, a command like

$ dbus-send --system --print-reply --dest=org.freedesktop.Hal \
            /org/freedesktop/Hal/devices/computer             \
            org.freedesktop.DBus.Introspectable.Introspect

will print out the introspection XML for what interfaces (ie. methods and signals) the given hal device object supports. For brevity, the org.freedesktop.Hal prefix have been stripped from the exceptions listed in the following sections.

Also note that other exceptions than the ones listed may be thrown; for example the org.freedesktop.Hal.Device.InterfaceLocked exception may be thrown regardless of how the interface is implemented (depending on if some other process is holding a lock on the device cf. Chapter 4, Locking); if PolicyKit support is enabled, the org.freedesktop.Hal.Device.PermissionDeniedByPolicy exception may be thrown (the two first words in the exception detail is resp. a) the privilege the caller didn't have; b) the textual result code from PolicyKit specifying if the caller can obtain the privilege) if the caller is not privileged and so on.

org.freedesktop.Hal.Manager interface

Only the /org/freedesktop/Hal/Manager object implements this interface. It's primarily used to discover devices. The following methods are available:

Method	Returns	Parameters	Throws	Description
GetAllDevices	Objref[]			Get all UDI's in the database.
DeviceExists	Bool			Determines if a given object exists.
FindDeviceStringMatch	Objref[]	String key, String value		Find devices for which the given string property assumes the given value.
FindDeviceByCapability	Objref[]	String capability		Finds devices of the given capability.
NewDevice	Objref		PermissionDenied	Creates a new device object in the temporary device list (TDL) and return the UDI. Caller must be uid 0.
Remove		Objref tmp_udi	NoSuchDevice, PermissionDenied	Removes a device object that was created in the TDL. Caller must be uid 0.
CommitToGdl		Objref tmp_udi, Objref udi	NoSuchDevice, PermissionDenied	Moves a device from the temporary device list (TDL) to the global device list (GDL). Caller must be uid 0.
AcquireGlobalInterfaceLock		String interface_name, Bool exclusive	Device.InterfaceAlreadyLocked	Acquires a global lock on an interface. See Chapter 4, Locking for details.
ReleaseGlobalInterfaceLock		String interface_name	Device.InterfaceNotLocked	Releases a global lock on an interface. See Chapter 4, Locking for details.
SingletonAddonIsReady		String command_line	PermissionDenied, SyntaxError	Called by singleton addons to signal that they are ready to handle devices. A singleton addon should implement the org.freedesktop.Hal.Singleton interface.

The following signals are emitted:

Signal	Parameters	Description
DeviceAdded	Objref obj	A device was added to the global device list (GDL).
DeviceRemoved	Objref obj	A device was removed from the global device list (GDL).
NewCapability	Objref obj, String cap	A device gained a new capability.
GlobalInterfaceLockAcquired	String lock_name, String lock_owner, Int num_holders	Sent when a process acquires a global interface lock.
GlobalInterfaceLockReleased	String lock_name, String lock_owner, Int num_holders	Sent when a process releases a global interface lock.

org.freedesktop.Hal.Device interface

Every hal device object (e.g. objects where the object path is prefixed with /org/freedesktop/Hal/devices/) implements this interface. It provides generic functionality. The following methods are available:

Method	Returns	Parameters	Throws	Description
GetProperty	Variant	String key	NoSuchProperty	Get property.
GetPropertyString	String	String key	NoSuchProperty, TypeMismatch	Get property.
GetPropertyStringList	String[]	String key	NoSuchProperty, TypeMismatch	Get property.
GetPropertyInteger	Int	String key	NoSuchProperty, TypeMismatch	Get property.
GetPropertyUInt64	UInt64	String key	NoSuchProperty, TypeMismatch	Get property.
GetPropertyBoolean	Bool	String key	NoSuchProperty, TypeMismatch	Get property.
GetPropertyDouble	Double	String key	NoSuchProperty, TypeMismatch	Get property.
SetProperty	Variant	String key	PermissionDenied	Set property.
SetPropertyString	String	String key	PermissionDenied, TypeMismatch	Set property.
SetPropertyStringList	String[]	String key	PermissionDenied, TypeMismatch	Set property.
SetPropertyInteger	Int	String key	PermissionDenied, TypeMismatch	Set property.
SetPropertyUInt64	UInt64	String key	PermissionDenied, TypeMismatch	Set property.
SetPropertyBoolean	Bool	String key	PermissionDenied, TypeMismatch	Set property.
SetPropertyDouble	Double	String key	PermissionDenied, TypeMismatch	Set property.
RemoveProperty		String key	NoSuchProperty, PermissionDenied	Remove a property.
GetPropertyType	Int	String key	NoSuchProperty	Get the type of a property. Returns the D-Bus type as an integer.
PropertyExists	Bool	String key		Determine if a property exists.
AddCapability		String capability	PermissionDenied	Adds a capability to a device.
QueryCapability	Bool	String capability		Determine if a device have a capability.
Lock	Bool	String reason	DeviceAlreadyLocked	Acquires an advisory lock on the device. Returns TRUE if the lock was acquired.
Unlock	Bool		DeviceNotLocked	Releases an advisory lock on the device. Returns TRUE if the lock was released.
AcquireInterfaceLock		String interface_name, Bool exclusive	PermissionDenied, Device.InterfaceAlreadyLocked	Acquires a lock on an interface for a specific device. See Chapter 4, Locking for details.
ReleaseInterfaceLock		String interface_name	PermissionDenied, Device.InterfaceNotLocked	Releases a lock on an interface for a specific device. See Chapter 4, Locking for details.
IsCallerLockedOut	Bool	String interface_name, String caller_unique_name	PermissionDenied	Determines whether a given process on the system message bus is locked out from an interface on a specific device. Only HAL helpers are privileged to use this method. See Chapter 4, Locking for details.
IsCallerPrivileged	String	String privilege, String caller_unique_name	PermissionDenied, Error	Determines whether a given process on the system message bus is authorized according to PolicyKit on a specific device for a specific PolicyKit privilege. Unprivileged callers (e.g. with a non-zero uid) can only ask about `caller_unique_name` that matches their own uid; if this is violated `PermissionDenied` will be thrown. This can be used ahead of time to see if a given call will succeed or if it requires privilege elevation (TODO: clarify this once PolicyKit can auth over D-Bus). Returns the textual representation of a PolKitResult value on success. If HAL is not built with PolicyKit support, this method always throws the `org.freedesktop.Hal.Device.Error` exception.
IsLockedByOthers	Bool	String interface_name		Determines whether a determines other processes than the caller holds a lock on the given device. See Chapter 4, Locking for details.
StringListAppend		String key, String value	PermissionDenied, TypeMismatch	Appends an item to a string list.
StringListPrepend		String key, String value	PermissionDenied, TypeMismatch	Prepends an item to a string list.
StringListRemove		String key, String value	PermissionDenied, TypeMismatch	Removes an item from a string list.
EmitCondition	Bool	String name, String details	PermissionDenied	Emit a condition on a device object.
Rescan	Bool		PermissionDenied	Force an updates of the properties of a device object by rereading data that is not monitored for changes.
Reprobe	Bool		PermissionDenied	Cause a synthetic remove and subsequent add of the given device object including all children beneath it. Will generate at least one pair of DeviceRemoved() and DeviceAdded() signals on the Manager interface.
ClaimInterface	Bool	String name, String introspection_xml	PermissionDenied	An addon can use this method for making the HAL daemon route all D-Bus calls on the given interface to the addon via the peer to peer D-Bus connection between the addon and the HAL daemon.
AddonIsReady	Bool		PermissionDenied	An addon needs to call this method when it's ready for the device to be announced on D-Bus. The rationale for this method is to allow an addon to modify the device object and claim interfaces before the device is announced on D-Bus.

The following signals are emitted:

Signal	Parameters	Description
PropertyModified	Int num_changes, Array of struct {String property_name, Bool added, Bool removed}	One or more properties on the device object have changed.
Condition	String name, String details	A generic mechanism used to specify a device condition that cannot be expressed in device properties. (NOTE: newly written code should use dedicated signals on a dedicated interface.).
InterfaceLockAcquired	String lock_name, String lock_owner, Int num_holders	Sent when a process acquires an interface lock on the device.
InterfaceLockReleased	String lock_name, String lock_owner, Int num_holders	Sent when a process releases an interface lock on the device.

org.freedesktop.Hal.Device.SystemPowerManagement interface

This interface provides a mechanism to affect system-wide power management. Normally only the root computer device object (/org/freedesktop/Hal/devices/computer) implements this interface. The following methods are available:

Method	Returns	Parameters	Throws	Description
Suspend	Int	Int num_secs_to_wakeup	SystemPowerManagement.NotSupported, SystemPowerManagement.AlarmNotSupported	Puts the system in a suspended state (typically ACPI S3) for `num_secs_to_wakeup` seconds. If the given time is zero, the system is put in the suspended state indefinitely. If wake-up isn't supported the the AlarmNotSupported exception is thrown. Latency for the system to return to an operational state is in the order of magnitude of 5 seconds.
Hibernate	Int		SystemPowerManagement.NotSupported	Save system state to persistent storage and power off the system (typically ACPI S4). Latency for the system to return to an operational state is in the order of magnitude of one minute.
SuspendHybrid	Int	Int num_secs_to_wakeup	SystemPowerManagement.NotSupported, SystemPowerManagement.AlarmNotSupported	Puts the system in a suspended state (typically ACPI S3) for `num_secs_to_wakeup` seconds but also write the system state to persistent storage so the system can resume even if power is removed. Like with Suspend(), if the given time is zero, the system is put in the suspended state indefinitely. If wake-up isn't supported the the AlarmNotSupported exception is thrown.
Shutdown	Int		SystemPowerManagement.NotSupported	Shut down the system.
Reboot	Int		SystemPowerManagement.NotSupported	Reboot the system.
SetPowerSave	Int	Bool should_save_power	SystemPowerManagement.NotSupported	If the boolean passed is TRUE, the system will be configured to save as much power as possible by e.g. enabling `laptop mode` to avoid spinning up disks. Typically, power management daemons will call this method when it determines that the system is running on battery power.