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Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-prepare-buf.rst')
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diff --git a/Documentation/media/uapi/v4l/vidioc-prepare-buf.rst b/Documentation/media/uapi/v4l/vidioc-prepare-buf.rst new file mode 100644 index 0000000..79076df --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-prepare-buf.rst @@ -0,0 +1,62 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_PREPARE_BUF: + +************************ +ioctl VIDIOC_PREPARE_BUF +************************ + +Name +==== + +VIDIOC_PREPARE_BUF - Prepare a buffer for I/O + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_buffer *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_PREPARE_BUF + +``argp`` + + +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` 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. In case such cache +operations are not required, the application can use one of +``V4L2_BUF_FLAG_NO_CACHE_INVALIDATE`` and +``V4L2_BUF_FLAG_NO_CACHE_CLEAN`` flags to skip the respective step. + +The :ref:`struct v4l2_buffer <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. |