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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/userspace-api/media/v4l/vidioc-querybuf.rst | |
parent | Initial commit. (diff) | |
download | linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.tar.xz linux-5d1646d90e1f2cceb9f0828f4b28318cd0ec7744.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/userspace-api/media/v4l/vidioc-querybuf.rst')
-rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-querybuf.rst | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-querybuf.rst b/Documentation/userspace-api/media/v4l/vidioc-querybuf.rst new file mode 100644 index 000000000..6c615e893 --- /dev/null +++ b/Documentation/userspace-api/media/v4l/vidioc-querybuf.rst @@ -0,0 +1,78 @@ +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L + +.. _VIDIOC_QUERYBUF: + +********************* +ioctl VIDIOC_QUERYBUF +********************* + +Name +==== + +VIDIOC_QUERYBUF - Query the status of a buffer + +Synopsis +======== + +.. c:macro:: VIDIOC_QUERYBUF + +``int ioctl(int fd, VIDIOC_QUERYBUF, struct v4l2_buffer *argp)`` + +Arguments +========= + +``fd`` + File descriptor returned by :c:func:`open()`. + +``argp`` + Pointer to struct :c:type:`v4l2_buffer`. + +Description +=========== + +This ioctl is part of the :ref:`streaming <mmap>` I/O method. It can +be used to query the status of a buffer at any time after buffers have +been allocated with the :ref:`VIDIOC_REQBUFS` ioctl. + +Applications set the ``type`` field of a struct +:c:type:`v4l2_buffer` to the same buffer type as was +previously used with struct :c:type:`v4l2_format` ``type`` +and struct :c:type:`v4l2_requestbuffers` ``type``, +and the ``index`` field. Valid index numbers range from zero to the +number of buffers allocated with +:ref:`VIDIOC_REQBUFS` (struct +:c:type:`v4l2_requestbuffers` ``count``) minus +one. The ``reserved`` and ``reserved2`` fields must be set to 0. When +using the :ref:`multi-planar API <planar-apis>`, the ``m.planes`` +field must contain a userspace pointer to an array of struct +:c:type:`v4l2_plane` and the ``length`` field has to be set +to the number of elements in that array. After calling +:ref:`VIDIOC_QUERYBUF` with a pointer to this structure drivers return an +error code or fill the rest of the structure. + +In the ``flags`` field the ``V4L2_BUF_FLAG_MAPPED``, +``V4L2_BUF_FLAG_PREPARED``, ``V4L2_BUF_FLAG_QUEUED`` and +``V4L2_BUF_FLAG_DONE`` flags will be valid. The ``memory`` field will be +set to the current I/O method. For the single-planar API, the +``m.offset`` contains the offset of the buffer from the start of the +device memory, the ``length`` field its size. For the multi-planar API, +fields ``m.mem_offset`` and ``length`` in the ``m.planes`` array +elements will be used instead and the ``length`` field of struct +:c:type:`v4l2_buffer` is set to the number of filled-in +array elements. The driver may or may not set the remaining fields and +flags, they are meaningless in this context. + +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. + +EINVAL + The buffer ``type`` is not supported, or the ``index`` is out of + bounds. |