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- .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
- .. c:namespace:: V4L
- .. _VIDIOC_PREPARE_BUF:
- ************************
- ioctl VIDIOC_PREPARE_BUF
- ************************
- Name
- ====
- VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
- Synopsis
- ========
- .. c:macro:: VIDIOC_PREPARE_BUF
- ``int ioctl(int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp)``
- Arguments
- =========
- ``fd``
- File descriptor returned by :c:func:`open()`.
- ``argp``
- Pointer to struct :c:type:`v4l2_buffer`.
- Description
- ===========
- Applications can optionally call the :ref:`VIDIOC_PREPARE_BUF` ioctl to
- pass ownership of the buffer to the driver before actually enqueuing it,
- using the :ref:`VIDIOC_QBUF <VIDIOC_QBUF>` ioctl, and to prepare it for future I/O. Such
- preparations may include cache invalidation or cleaning. Performing them
- in advance saves time during the actual I/O.
- The struct :c:type:`v4l2_buffer` structure is specified in
- :ref:`buffer`.
- Return Value
- ============
- On success 0 is returned, on error -1 and the ``errno`` variable is set
- appropriately. The generic error codes are described at the
- :ref:`Generic Error Codes <gen-errors>` chapter.
- EBUSY
- File I/O is in progress.
- EINVAL
- The buffer ``type`` is not supported, or the ``index`` is out of
- bounds, or no buffers have been allocated yet, or the ``userptr`` or
- ``length`` are invalid.
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