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