1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: V4L 3 4 .. _VIDIOC_PREPARE_BUF: 5 6 ************************ 7 ioctl VIDIOC_PREPARE_BUF 8 ************************ 9 10 Name 11 ==== 12 13 VIDIOC_PREPARE_BUF - Prepare a buffer for I/O 14 15 Synopsis 16 ======== 17 18 .. c:macro:: VIDIOC_PREPARE_BUF 19 20 ``int ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)`` 21 22 Arguments 23 ========= 24 25 ``fd`` 26 File descriptor returned by :c:func:`open()`. 27 28 ``argp`` 29 Pointer to struct :c:type:`v4l2_buffer`. 30 31 Description 32 =========== 33 34 Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to 35 pass ownership of the buffer to the driver before actually enqueuing it, 36 using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such 37 preparations may include cache invalidation or cleaning. Performing them 38 in advance saves time during the actual I/O. 39 40 The struct :c:type:`v4l2_buffer` structure is specified in 41 :ref:`buffer`. 42 43 Return Value 44 ============ 45 46 On success 0 is returned, on error -1 and the ``errno`` variable is set 47 appropriately. The generic error codes are described at the 48 :ref:`Generic Error Codes <gen-errors>` chapter. 49 50 EBUSY 51 File I/O is in progress. 52 53 EINVAL 54 The buffer ``type`` is not supported, or the ``index`` is out of 55 bounds, or no buffers have been allocated yet, or the ``userptr`` or 56 ``length`` are invalid.
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