1 .. Permission is granted to copy, distribute and/or modify this
2 .. document under the terms of the GNU Free Documentation License,
3 .. Version 1.1 or any later version published by the Free Software
4 .. Foundation, with no Invariant Sections, no Front-Cover Texts
5 .. and no Back-Cover Texts. A copy of the license is included at
6 .. Documentation/media/uapi/fdl-appendix.rst.
8 .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
10 .. _VIDIOC_PREPARE_BUF:
12 ************************
13 ioctl VIDIOC_PREPARE_BUF
14 ************************
19 VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
25 .. c:function:: int ioctl( int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp )
26 :name: VIDIOC_PREPARE_BUF
33 File descriptor returned by :ref:`open() <func-open>`.
36 Pointer to struct :c:type:`v4l2_buffer`.
42 Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
43 pass ownership of the buffer to the driver before actually enqueuing it,
44 using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such
45 preparations may include cache invalidation or cleaning. Performing them
46 in advance saves time during the actual I/O. In case such cache
47 operations are not required, the application can use one of
48 ``V4L2_BUF_FLAG_NO_CACHE_INVALIDATE`` and
49 ``V4L2_BUF_FLAG_NO_CACHE_CLEAN`` flags to skip the respective step.
51 The struct :c:type:`v4l2_buffer` structure is specified in
58 On success 0 is returned, on error -1 and the ``errno`` variable is set
59 appropriately. The generic error codes are described at the
60 :ref:`Generic Error Codes <gen-errors>` chapter.
63 File I/O is in progress.
66 The buffer ``type`` is not supported, or the ``index`` is out of
67 bounds, or no buffers have been allocated yet, or the ``userptr`` or
68 ``length`` are invalid.