1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L
3
4 .. _VIDIOC_SUBDEV_G_CLIENT_CAP:
5
6 ************************************************************
7 ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP
8 ************************************************************
9
10 Name
11 ====
12
13 VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client
14 capabilities.
15
16 Synopsis
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
27 Arguments
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
36 Description
37 ===========
38
39 These ioctls are used to get and set the client (the application using the
40 subdevice ioctls) capabilities. The client capabilities are stored in the file
41 handle of the opened subdev device node, and the client must set the
42 capabilities for each opened subdev separately.
43
44 By default no client capabilities are set when a subdev device node is opened.
45
46 The purpose of the client capabilities are to inform the kernel of the behavior
47 of the client, mainly related to maintaining compatibility with different
48 kernel and userspace versions.
49
50 The ``VIDIOC_SUBDEV_G_CLIENT_CAP`` ioctl returns the current client capabilities
51 associated with the file handle ``fd``.
52
53 The ``VIDIOC_SUBDEV_S_CLIENT_CAP`` ioctl sets client capabilities for the file
54 handle ``fd``. The new capabilities fully replace the current capabilities, the
55 ioctl can therefore also be used to remove capabilities that have previously
56 been set.
57
58 ``VIDIOC_SUBDEV_S_CLIENT_CAP`` modifies the struct
59 :c:type:`v4l2_subdev_client_capability` to reflect the capabilities that have
60 been accepted. A common case for the kernel not accepting a capability is that
61 the kernel is older than the headers the userspace uses, and thus the capability
62 is unknown to the kernel.
63
64 .. tabularcolumns:: |p{1.5cm}|p{2.9cm}|p{12.9cm}|
65
66 .. c:type:: v4l2_subdev_client_capability
67
68 .. flat-table:: struct v4l2_subdev_client_capability
69 :header-rows: 0
70 :stub-columns: 0
71 :widths: 3 4 20
72
73 * - __u64
74 - ``capabilities``
75 - Sub-device client capabilities of the opened device.
76
77 .. tabularcolumns:: |p{6.8cm}|p{2.4cm}|p{8.1cm}|
78
79 .. flat-table:: Client Capabilities
80 :header-rows: 1
81
82 * - Capability
83 - Description
84 * - ``V4L2_SUBDEV_CLIENT_CAP_STREAMS``
85 - The client is aware of streams. Setting this flag enables the use
86 of 'stream' fields (referring to the stream number) with various
87 ioctls. If this is not set (which is the default), the 'stream' fields
88 will be forced to 0 by the kernel.
89 * - ``V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH``
90 - The client is aware of the :c:type:`v4l2_subdev_frame_interval`
91 ``which`` field. If this is not set (which is the default), the
92 ``which`` field is forced to ``V4L2_SUBDEV_FORMAT_ACTIVE`` by the
93 kernel.
94
95 Return Value
96 ============
97
98 On success 0 is returned, on error -1 and the ``errno`` variable is set
99 appropriately. The generic error codes are described at the
100 :ref:`Generic Error Codes <gen-errors>` chapter.
101
102 ENOIOCTLCMD
103 The kernel does not support this ioctl.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.