Documentation/linux_tv/media/v4l/func-ioctl.rst

   1 .. -*- coding: utf-8; mode: rst -*-
   2
   3 .. _func-ioctl:
   4
   5 ************
   6 V4L2 ioctl()
   7 ************
   8
   9 *man v4l2-ioctl(2)*
  10
  11 Program a V4L2 device
  12
  13
  14 Synopsis
  15 ========
  16
  17 .. code-block:: c
  18
  19     #include <sys/ioctl.h>
  20
  21
  22 .. cpp:function:: int ioctl( int fd, int request, void *argp )
  23
  24 Arguments
  25 =========
  26
  27 ``fd``
  28     File descriptor returned by :ref:`open() <func-open>`.
  29
  30 ``request``
  31     V4L2 ioctl request code as defined in the ``videodev2.h`` header
  32     file, for example VIDIOC_QUERYCAP.
  33
  34 ``argp``
  35     Pointer to a function parameter, usually a structure.
  36
  37
  38 Description
  39 ===========
  40
  41 The :c:func:`ioctl()` function is used to program V4L2 devices. The
  42 argument ``fd`` must be an open file descriptor. An ioctl ``request``
  43 has encoded in it whether the argument is an input, output or read/write
  44 parameter, and the size of the argument ``argp`` in bytes. Macros and
  45 defines specifying V4L2 ioctl requests are located in the
  46 ``videodev2.h`` header file. Applications should use their own copy, not
  47 include the version in the kernel sources on the system they compile on.
  48 All V4L2 ioctl requests, their respective function and parameters are
  49 specified in :ref:`user-func`.
  50
  51
  52 Return Value
  53 ============
  54
  55 On success 0 is returned, on error -1 and the ``errno`` variable is set
  56 appropriately. The generic error codes are described at the
  57 :ref:`Generic Error Codes <gen-errors>` chapter.
  58
  59 When an ioctl that takes an output or read/write parameter fails, the
  60 parameter remains unmodified.
  61
  62
  63 .. ------------------------------------------------------------------------------
  64 .. This file was automatically converted from DocBook-XML with the dbxml
  65 .. library (https://github.com/return42/sphkerneldoc). The origin XML comes
  66 .. from the linux kernel, refer to:
  67 ..
  68 .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook
  69 .. ------------------------------------------------------------------------------