6.7. ioctl MEDIA_IOC_ENUM_LINKS¶
6.7.1. Name¶
MEDIA_IOC_ENUM_LINKS - Enumerate all pads and links for a given entity
6.7.2. Synopsis¶
-
int
ioctl
(int fd, MEDIA_IOC_ENUM_LINKS, struct media_links_enum *argp)¶
6.7.3. Arguments¶
fd
- File descriptor returned by open().
argp
- Pointer to struct
media_links_enum
.
6.7.4. 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
¶
__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
¶
__u32 | entity |
ID of the entity this pad belongs to. |
__u16 | index |
Pad index, starts at 0. |
__u32 | flags |
Pad flags, see Media pad flags for more details. |
__u32 | reserved[2] |
Reserved for future extensions. Drivers and applications must set the array to zero. |
-
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. |
__u32 | reserved[4] |
Reserved for future extensions. Drivers and applications must set the array to zero. |
6.7.5. 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.