4.7. ioctl MEDIA_IOC_ENUM_LINKS

4.7.1. Name

MEDIA_IOC_ENUM_LINKS - Enumerate all pads and links for a given entity

4.7.2. Synopsis

int ioctl(int fd, MEDIA_IOC_ENUM_LINKS, struct media_links_enum *argp)

4.7.3. Arguments

fd

File descriptor returned by open().

argp

4.7.4. Description

To enumerate pads and/or links for a given entity, applications set the entity field of a struct media_links_enum structure and initialize the struct media_pad_desc and struct media_link_desc structure arrays pointed by the pads and links fields. They then call the MEDIA_IOC_ENUM_LINKS ioctl with a pointer to this structure.

If the pads field is not NULL, the driver fills the pads array with information about the entity’s pads. The array must have enough room to store all the entity’s pads. The number of pads can be retrieved with ioctl MEDIA_IOC_ENUM_ENTITIES.

If the links field is not NULL, the driver fills the links array with information about the entity’s outbound links. The array must have enough room to store all the entity’s outbound links. The number of outbound links can be retrieved with ioctl MEDIA_IOC_ENUM_ENTITIES.

Only forward links that originate at one of the entity’s source pads are returned during the enumeration process.

media_links_enum

struct media_links_enum

__u32	entity	Entity id, set by the application.
struct media_pad_desc	*pads	Pointer to a pads array allocated by the application. Ignored if NULL.
struct media_link_desc	*links	Pointer to a links array allocated by the application. Ignored if NULL.

media_pad_desc

struct media_pad_desc

__u32	entity	ID of the entity this pad belongs to.
__u16	index	0-based pad index.
__u32	flags	Pad flags, see Media pad flags for more details.

media_link_desc

struct media_link_desc

struct media_pad_desc	source	Pad at the origin of this link.
struct media_pad_desc	sink	Pad at the target of this link.
__u32	flags	Link flags, see Media link flags for more details.

4.7.5. 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.

EINVAL

The struct media_links_enum id references a non-existing entity.