ioctl MEDIA_IOC_G_TOPOLOGY
&manvol;

# MEDIA_IOC_G_TOPOLOGY

Enumerate the graph topology and graph element properties

    	int ioctl
    	int fd
    	int request
    	struct media_v2_topology *argp

## Arguments

`fd`

  File descriptor returned by `open()`.

`request`

  MEDIA_IOC_G_TOPOLOGY

`argp`

## Description

The typical usage of this ioctl is to call it twice. On the first call, the structure defined at &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.

### 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`

### 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 for details.
__u32 | reserved[12] | Reserved for future extensions. Drivers and applications must set this array to zero.

### struct media_v2_interface

__u32 | id |  |  | Unique ID for the interface.
__u32 | intf_type |  |  | Interface type, see 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 for details..

### struct media_v2_interface

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

### 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 for more details.
__u32 | reserved[9] |  |  | Reserved for future extensions. Drivers and applications must set this array to zero.

### 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 for more details.
__u32 | reserved[5] |  |  | Reserved for future extensions. Drivers and applications must set this array to zero.

&return-value;

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.