diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/buffer.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/buffer.rst | 53 |
1 files changed, 16 insertions, 37 deletions
diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst index 9149b57728e5..3112300c2fa0 100644 --- a/Documentation/media/uapi/v4l/buffer.rst +++ b/Documentation/media/uapi/v4l/buffer.rst @@ -172,11 +172,10 @@ struct v4l2_buffer .. flat-table:: struct v4l2_buffer :header-rows: 0 :stub-columns: 0 - :widths: 1 2 1 10 + :widths: 1 2 10 * - __u32 - ``index`` - - - Number of the buffer, set by the application except when calling :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, then it is set by the driver. This field can range from zero to the number of buffers @@ -186,14 +185,12 @@ struct v4l2_buffer :ref:`VIDIOC_CREATE_BUFS` minus one. * - __u32 - ``type`` - - - Type of the buffer, same as struct :c:type:`v4l2_format` ``type`` or struct :c:type:`v4l2_requestbuffers` ``type``, set by the application. See :c:type:`v4l2_buf_type` * - __u32 - ``bytesused`` - - - The number of bytes occupied by the data in the buffer. It depends on the negotiated data format and may change with each buffer for compressed variable size data like JPEG images. Drivers must set @@ -205,18 +202,15 @@ struct v4l2_buffer ``planes`` pointer is used instead. * - __u32 - ``flags`` - - - Flags set by the application or driver, see :ref:`buffer-flags`. * - __u32 - ``field`` - - - Indicates the field order of the image in the buffer, see :c:type:`v4l2_field`. This field is not used when the buffer contains VBI data. Drivers must set it when ``type`` refers to a capture stream, applications when it refers to an output stream. * - struct timeval - ``timestamp`` - - - For capture streams this is time when the first data byte was captured, as returned by the :c:func:`clock_gettime()` function for the relevant clock id; see ``V4L2_BUF_FLAG_TIMESTAMP_*`` in @@ -229,7 +223,6 @@ struct v4l2_buffer stream. * - struct :c:type:`v4l2_timecode` - ``timecode`` - - - When the ``V4L2_BUF_FLAG_TIMECODE`` flag is set in ``flags``, this structure contains a frame timecode. In :c:type:`V4L2_FIELD_ALTERNATE <v4l2_field>` mode the top and @@ -239,10 +232,9 @@ struct v4l2_buffer independent of the ``timestamp`` and ``sequence`` fields. * - __u32 - ``sequence`` - - - Set by the driver, counting the frames (not fields!) in sequence. This field is set for both input and output devices. - * - :cspan:`3` + * - :cspan:`2` In :c:type:`V4L2_FIELD_ALTERNATE <v4l2_field>` mode the top and bottom field have the same sequence number. The count starts at @@ -262,13 +254,11 @@ struct v4l2_buffer * - __u32 - ``memory`` - - - This field must be set by applications and/or drivers in accordance with the selected I/O method. See :c:type:`v4l2_memory` - * - union + * - union { - ``m`` - * - - - __u32 + * - __u32 - ``offset`` - For the single-planar API and when ``memory`` is ``V4L2_MEMORY_MMAP`` this is the offset of the buffer from the @@ -276,29 +266,27 @@ struct v4l2_buffer and apart of serving as parameter to the :ref:`mmap() <func-mmap>` function not useful for applications. See :ref:`mmap` for details - * - - - unsigned long + * - unsigned long - ``userptr`` - For the single-planar API and when ``memory`` is ``V4L2_MEMORY_USERPTR`` this is a pointer to the buffer (casted to unsigned long type) in virtual memory, set by the application. See :ref:`userp` for details. - * - - - struct v4l2_plane + * - struct v4l2_plane - ``*planes`` - When using the multi-planar API, contains a userspace pointer to an array of struct :c:type:`v4l2_plane`. The size of the array should be put in the ``length`` field of this struct :c:type:`v4l2_buffer` structure. - * - - - int + * - int - ``fd`` - For the single-plane API and when ``memory`` is ``V4L2_MEMORY_DMABUF`` this is the file descriptor associated with a DMABUF buffer. + * - } + - * - __u32 - ``length`` - - - Size of the buffer (not the payload) in bytes for the single-planar API. This is set by the driver based on the calls to :ref:`VIDIOC_REQBUFS` and/or @@ -308,12 +296,10 @@ struct v4l2_buffer actual number of valid elements in that array. * - __u32 - ``reserved2`` - - - A place holder for future extensions. Drivers and applications must set this to 0. * - __u32 - ``request_fd`` - - - The file descriptor of the request to queue the buffer to. If the flag ``V4L2_BUF_FLAG_REQUEST_FD`` is set, then the buffer will be queued to this request. If the flag is not set, then this field will @@ -344,11 +330,10 @@ struct v4l2_plane .. flat-table:: :header-rows: 0 :stub-columns: 0 - :widths: 1 1 1 2 + :widths: 1 1 2 * - __u32 - ``bytesused`` - - - The number of bytes occupied by data in the plane (its payload). Drivers must set this field when ``type`` refers to a capture stream, applications when it refers to an output stream. If the @@ -362,40 +347,35 @@ struct v4l2_plane which may not be 0. * - __u32 - ``length`` - - - Size in bytes of the plane (not its payload). This is set by the driver based on the calls to :ref:`VIDIOC_REQBUFS` and/or :ref:`VIDIOC_CREATE_BUFS`. - * - union + * - union { - ``m`` - - - - - * - - - __u32 + * - __u32 - ``mem_offset`` - When the memory type in the containing struct :c:type:`v4l2_buffer` is ``V4L2_MEMORY_MMAP``, this is the value that should be passed to :ref:`mmap() <func-mmap>`, similar to the ``offset`` field in struct :c:type:`v4l2_buffer`. - * - - - unsigned long + * - unsigned long - ``userptr`` - When the memory type in the containing struct :c:type:`v4l2_buffer` is ``V4L2_MEMORY_USERPTR``, this is a userspace pointer to the memory allocated for this plane by an application. - * - - - int + * - int - ``fd`` - When the memory type in the containing struct :c:type:`v4l2_buffer` is ``V4L2_MEMORY_DMABUF``, this is a file descriptor associated with a DMABUF buffer, similar to the ``fd`` field in struct :c:type:`v4l2_buffer`. + * - } + - * - __u32 - ``data_offset`` - - - Offset in bytes to video data in the plane. Drivers must set this field when ``type`` refers to a capture stream, applications when it refers to an output stream. @@ -407,7 +387,6 @@ struct v4l2_plane at offset ``data_offset`` from the start of the plane. * - __u32 - ``reserved[11]`` - - - Reserved for future use. Should be zeroed by drivers and applications. |