Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 61 insertions, 0 deletions

diff --git a/Documentation/media/uapi/v4l/vidioc-prepare-buf.rst b/Documentation/media/uapi/v4l/vidioc-prepare-buf.rst
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+.. -*- coding: utf-8; mode: rst -*-
+
+.. _VIDIOC_PREPARE_BUF:
+
+************************
+ioctl VIDIOC_PREPARE_BUF
+************************
+
+Name
+====
+
+VIDIOC_PREPARE_BUF - Prepare a buffer for I/O
+
+
+Synopsis
+========
+
+.. c:function:: int ioctl( int fd, VIDIOC_PREPARE_BUF, struct v4l2_buffer *argp )
+    :name: VIDIOC_PREPARE_BUF
+
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <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. 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 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.