Name

MEDIA_IOC_ENUM_LINKS — Enumerate all pads and links for a given entity

Synopsis

int ioctl(int fd,
 int request,
 struct media_links_enum *argp);
 

Arguments

fd

File descriptor returned by open().

request

MEDIA_IOC_ENUM_LINKS

argp

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 the MEDIA_IOC_ENUM_ENTITIES ioctl.

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 the MEDIA_IOC_ENUM_ENTITIES ioctl.

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

Table L.5. struct media_links_enum

__u32entityEntity id, set by the application.
struct struct media_pad_desc*padsPointer to a pads array allocated by the application. Ignored if NULL.
struct struct media_link_desc*linksPointer to a links array allocated by the application. Ignored if NULL.

Table L.6. struct media_pad_desc

__u32entityID of the entity this pad belongs to.
__u16index0-based pad index.
__u32flagsPad flags, see Table L.7, “Media pad flags” for more details.

Table L.7. Media pad flags

MEDIA_PAD_FL_SINKInput pad, relative to the entity. Input pads sink data and are targets of links.
MEDIA_PAD_FL_SOURCEOutput pad, relative to the entity. Output pads source data and are origins of links.
MEDIA_PAD_FL_MUST_CONNECTIf this flag is set and the pad is linked to any other pad, then at least one of those links must be enabled for the entity to be able to stream. There could be temporary reasons (e.g. device configuration dependent) for the pad to need enabled links even when this flag isn't set; the absence of the flag doesn't imply there is none.

Table L.8. struct media_link_desc

struct struct media_pad_descsourcePad at the origin of this link.
struct struct media_pad_descsinkPad at the target of this link.
__u32flagsLink flags, see Table L.9, “Media link flags” for more details.

Table L.9. Media link flags

MEDIA_LNK_FL_ENABLEDThe link is enabled and can be used to transfer media data. When two or more links target a sink pad, only one of them can be enabled at a time.
MEDIA_LNK_FL_IMMUTABLEThe link enabled state can't be modified at runtime. An immutable link is always enabled.
MEDIA_LNK_FL_DYNAMICThe link enabled state can be modified during streaming. This flag is set by drivers and is read-only for applications.

One and only one of MEDIA_PAD_FL_SINK and MEDIA_PAD_FL_SOURCE must be set for every pad.

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.