From 60c2820d0f6d3497975b6488e2599f8f611d8b95 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab Date: Fri, 8 Jul 2016 11:40:06 -0300 Subject: doc_rst: rename the media Sphinx suff to Documentation/media The name of the subsystem is "media", and not "linux_tv". Also, as we plan to add other stuff there in the future, let's rename also the media uAPI book to media_uapi, to make it clearer. No functional changes. Signed-off-by: Mauro Carvalho Chehab --- Documentation/media/uapi/v4l/vidioc-querybuf.rst | 81 ++++++++++++++++++++++++ 1 file changed, 81 insertions(+) create mode 100644 Documentation/media/uapi/v4l/vidioc-querybuf.rst (limited to 'Documentation/media/uapi/v4l/vidioc-querybuf.rst') diff --git a/Documentation/media/uapi/v4l/vidioc-querybuf.rst b/Documentation/media/uapi/v4l/vidioc-querybuf.rst new file mode 100644 index 0000000000000..32af6f7b50605 --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-querybuf.rst @@ -0,0 +1,81 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _VIDIOC_QUERYBUF: + +********************* +ioctl VIDIOC_QUERYBUF +********************* + +Name +==== + +VIDIOC_QUERYBUF - Query the status of a buffer + + +Synopsis +======== + +.. cpp:function:: int ioctl( int fd, int request, struct v4l2_buffer *argp ) + + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() `. + +``request`` + VIDIOC_QUERYBUF + +``argp`` + + +Description +=========== + +This ioctl is part of the :ref:`streaming ` 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 +:ref:`v4l2_buffer ` to the same buffer type as was +previously used with struct :ref:`v4l2_format ` ``type`` +and struct :ref:`v4l2_requestbuffers ` ``type``, +and the ``index`` field. Valid index numbers range from zero to the +number of buffers allocated with +:ref:`VIDIOC_REQBUFS` (struct +:ref:`v4l2_requestbuffers ` ``count``) minus +one. The ``reserved`` and ``reserved2`` fields must be set to 0. When +using the :ref:`multi-planar API `, the ``m.planes`` +field must contain a userspace pointer to an array of struct +:ref:`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 +:ref:`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 :ref:`struct 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 ` chapter. + +EINVAL + The buffer ``type`` is not supported, or the ``index`` is out of + bounds. -- cgit v1.2.3