diff options
Diffstat (limited to 'Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst | 58 |
1 files changed, 44 insertions, 14 deletions
diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst index 50ea72043bb0..daf9a6621b50 100644 --- a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst +++ b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst @@ -73,6 +73,8 @@ aborting or finishing any DMA in progress, an implicit .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| +.. cssclass:: longtable + .. flat-table:: struct v4l2_requestbuffers :header-rows: 0 :stub-columns: 0 @@ -104,10 +106,13 @@ aborting or finishing any DMA in progress, an implicit ``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will free any previously allocated buffers, so this is typically something that will be done at the start of the application. - * - __u32 - - ``reserved``\ [1] - - A place holder for future extensions. Drivers and applications - must set the array to zero. + * - __u8 + - ``flags`` + - Specifies additional buffer management attributes. + See :ref:`memory-flags`. + * - __u8 + - ``reserved``\ [3] + - Reserved for future extensions. .. _v4l2-buf-capabilities: .. _V4L2-BUF-CAP-SUPPORTS-MMAP: @@ -117,14 +122,8 @@ aborting or finishing any DMA in progress, an implicit .. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS: .. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF: .. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS: - -.. raw:: latex - - \footnotesize - -.. tabularcolumns:: |p{8.1cm}|p{2.2cm}|p{7.0cm}| - -.. cssclass:: longtable +.. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS: +.. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS: .. flat-table:: V4L2 Buffer Capabilities Flags :header-rows: 0 @@ -158,8 +157,39 @@ aborting or finishing any DMA in progress, an implicit - This capability is set by the driver to indicate that the queue supports cache and memory management hints. However, it's only valid when the queue is used for :ref:`memory mapping <mmap>` streaming I/O. See - :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>` and - :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>`. + :ref:`V4L2_BUF_FLAG_NO_CACHE_INVALIDATE <V4L2-BUF-FLAG-NO-CACHE-INVALIDATE>`, + :ref:`V4L2_BUF_FLAG_NO_CACHE_CLEAN <V4L2-BUF-FLAG-NO-CACHE-CLEAN>` and + :ref:`V4L2_MEMORY_FLAG_NON_COHERENT <V4L2-MEMORY-FLAG-NON-COHERENT>`. + * - ``V4L2_BUF_CAP_SUPPORTS_MAX_NUM_BUFFERS`` + - 0x00000080 + - If set, then the ``max_num_buffers`` field in ``struct v4l2_create_buffers`` + is valid. If not set, then the maximum is ``VIDEO_MAX_FRAME`` buffers. + * - ``V4L2_BUF_CAP_SUPPORTS_REMOVE_BUFS`` + - 0x00000100 + - If set, then ``VIDIOC_REMOVE_BUFS`` is supported. + +.. _memory-flags: +.. _V4L2-MEMORY-FLAG-NON-COHERENT: + +.. flat-table:: Memory Consistency Flags + :header-rows: 0 + :stub-columns: 0 + :widths: 3 1 4 + + * - ``V4L2_MEMORY_FLAG_NON_COHERENT`` + - 0x00000001 + - A buffer is allocated either in coherent (it will be automatically + coherent between the CPU and the bus) or non-coherent memory. The + latter can provide performance gains, for instance the CPU cache + sync/flush operations can be avoided if the buffer is accessed by the + corresponding device only and the CPU does not read/write to/from that + buffer. However, this requires extra care from the driver -- it must + guarantee memory consistency by issuing a cache flush/sync when + consistency is needed. If this flag is set V4L2 will attempt to + allocate the buffer in non-coherent memory. The flag takes effect + only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the + queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS + <V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability. .. raw:: latex |