4.5. ioctl MEDIA_IOC_G_TOPOLOGY

4.5.1. Name

MEDIA_IOC_G_TOPOLOGY - Enumerate the graph topology and graph element properties

4.5.2. Synopsis

int ioctl(int fd, MEDIA_IOC_G_TOPOLOGY, struct media_v2_topology *argp)

4.5.3. Arguments

fd

File descriptor returned by open().

argp

4.5.4. Description

The typical usage of this ioctl is to call it twice. On the first call, the structure defined at struct media_v2_topology should be zeroed. At return, if no errors happen, this ioctl will return the topology_version and the total number of entities, interfaces, pads and links.

Before the second call, the userspace should allocate arrays to store the graph elements that are desired, putting the pointers to them at the ptr_entities, ptr_interfaces, ptr_links and/or ptr_pads, keeping the other values untouched.

If the topology_version remains the same, the ioctl should fill the desired arrays with the media graph elements.

media_v2_topology

struct media_v2_topology

__u64	topology_version	Version of the media graph topology. When the graph is created, this field starts with zero. Every time a graph element is added or removed, this field is incremented.
__u64	num_entities	Number of entities in the graph
__u64	ptr_entities	A pointer to a memory area where the entities array will be stored, converted to a 64-bits integer. It can be zero. if zero, the ioctl won’t store the entities. It will just update num_entities
__u64	num_interfaces	Number of interfaces in the graph
__u64	ptr_interfaces	A pointer to a memory area where the interfaces array will be stored, converted to a 64-bits integer. It can be zero. if zero, the ioctl won’t store the interfaces. It will just update num_interfaces
__u64	num_pads	Total number of pads in the graph
__u64	ptr_pads	A pointer to a memory area where the pads array will be stored, converted to a 64-bits integer. It can be zero. if zero, the ioctl won’t store the pads. It will just update num_pads
__u64	num_links	Total number of data and interface links in the graph
__u64	ptr_links	A pointer to a memory area where the links array will be stored, converted to a 64-bits integer. It can be zero. if zero, the ioctl won’t store the links. It will just update num_links

media_v2_entity

struct media_v2_entity

__u32	id	Unique ID for the entity.
char	name[64]	Entity name as an UTF-8 NULL-terminated string.
__u32	function	Entity main function, see Media entity types for details.
__u32	reserved[12]	Reserved for future extensions. Drivers and applications must set this array to zero.

media_v2_interface

struct media_v2_interface

__u32	id	Unique ID for the interface.
__u32	intf_type	Interface type, see Media interface types for details.
__u32	flags	Interface flags. Currently unused.
__u32	reserved[9]	Reserved for future extensions. Drivers and applications must set this array to zero.
struct media_v2_intf_devnode	devnode	Used only for device node interfaces. See media_v2_intf_devnode for details..

media_v2_intf_devnode

struct media_v2_interface

__u32	major	Device node major number.
__u32	minor	Device node minor number.

media_v2_pad

struct media_v2_pad

__u32	id	Unique ID for the pad.
__u32	entity_id	Unique ID for the entity where this pad belongs.
__u32	flags	Pad flags, see Media pad flags for more details.
__u32	reserved[9]	Reserved for future extensions. Drivers and applications must set this array to zero.

media_v2_link

struct media_v2_pad

__u32	id	Unique ID for the pad.
__u32	source_id	On pad to pad links: unique ID for the source pad. On interface to entity links: unique ID for the interface.
__u32	sink_id	On pad to pad links: unique ID for the sink pad. On interface to entity links: unique ID for the entity.
__u32	flags	Link flags, see Media link flags for more details.
__u32	reserved[5]	Reserved for future extensions. Drivers and applications must set this array to zero.

4.5.5. Return Value

On success 0 is returned, on error -1 and the errno variable is set appropriately. The generic error codes are described at the Generic Error Codes chapter.

ENOSPC

This is returned when either one or more of the num_entities, num_interfaces, num_links or num_pads are non-zero and are smaller than the actual number of elements inside the graph. This may happen if the topology_version changed when compared to the last time this ioctl was called. Userspace should usually free the area for the pointers, zero the struct elements and call this ioctl again.