1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_SUBDEV_G_CLIENT_CAP:
5
6************************************************************
7ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP
8************************************************************
9
10Name
11====
12
13VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client
14capabilities.
15
16Synopsis
17========
18
19.. c:macro:: VIDIOC_SUBDEV_G_CLIENT_CAP
20
21``int ioctl(int fd, VIDIOC_SUBDEV_G_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
22
23.. c:macro:: VIDIOC_SUBDEV_S_CLIENT_CAP
24
25``int ioctl(int fd, VIDIOC_SUBDEV_S_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
26
27Arguments
28=========
29
30``fd``
31    File descriptor returned by :ref:`open() <func-open>`.
32
33``argp``
34    Pointer to struct :c:type:`v4l2_subdev_client_capability`.
35
36Description
37===========
38
39These ioctls are used to get and set the client (the application using the
40subdevice ioctls) capabilities. The client capabilities are stored in the file
41handle of the opened subdev device node, and the client must set the
42capabilities for each opened subdev separately.
43
44By default no client capabilities are set when a subdev device node is opened.
45
46The purpose of the client capabilities are to inform the kernel of the behavior
47of the client, mainly related to maintaining compatibility with different
48kernel and userspace versions.
49
50The ``VIDIOC_SUBDEV_G_CLIENT_CAP`` ioctl returns the current client capabilities
51associated with the file handle ``fd``.
52
53The ``VIDIOC_SUBDEV_S_CLIENT_CAP`` ioctl sets client capabilities for the file
54handle ``fd``. The new capabilities fully replace the current capabilities, the
55ioctl can therefore also be used to remove capabilities that have previously
56been set.
57
58``VIDIOC_SUBDEV_S_CLIENT_CAP`` modifies the struct
59:c:type:`v4l2_subdev_client_capability` to reflect the capabilities that have
60been accepted. A common case for the kernel not accepting a capability is that
61the kernel is older than the headers the userspace uses, and thus the capability
62is unknown to the kernel.
63
64.. flat-table:: Client Capabilities
65    :header-rows:  1
66
67    * - Capability
68      - Description
69    * - ``V4L2_SUBDEV_CLIENT_CAP_STREAMS``
70      - The client is aware of streams. Setting this flag enables the use
71        of 'stream' fields (referring to the stream number) with various
72        ioctls. If this is not set (which is the default), the 'stream' fields
73        will be forced to 0 by the kernel.
74
75Return Value
76============
77
78On success 0 is returned, on error -1 and the ``errno`` variable is set
79appropriately. The generic error codes are described at the
80:ref:`Generic Error Codes <gen-errors>` chapter.
81
82ENOIOCTLCMD
83   The kernel does not support this ioctl.
84