MEDIA_IOC_G_TOPOLOGY — Enumerate the graph topology and graph element properties
int ioctl( | int fd, |
| int request, | |
struct media_v2_topology *argp); |
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.
Table L.2. 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 |
Table L.3. 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 Table 16.1, “Media entity types” for details. | ||
| __u32 | reserved[12] | Reserved for future extensions. Drivers and applications must set this array to zero. |
Table L.4. struct media_v2_interface
| __u32 | id | Unique ID for the interface. | ||
| __u32 | intf_type | Interface type, see Table 16.3, “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 Table L.5, “struct media_v2_interface” for details.. |
Table L.5. struct media_v2_interface
| __u32 | major | Device node major number. | ||
| __u32 | minor | Device node minor number. |
Table L.6. 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 Table 16.4, “Media pad flags” for more details. | ||
| __u32 | reserved[9] | Reserved for future extensions. Drivers and applications must set this array to zero. |
Table L.7. 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 Table 16.5, “Media link flags” for more details. | ||
| __u32 | reserved[5] | Reserved for future extensions. Drivers and applications must set this array to zero. |
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.
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.