Commit 965c1e0b authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Mauro Carvalho Chehab
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media: videobuf2: add V4L2_MEMORY_FLAG_NON_COHERENT flag 



By setting or clearing the V4L2_MEMORY_FLAG_NON_COHERENT flag
user-space should be able to hint vb2 that either non-coherent
(if supported) or coherent memory should be used for the buffer
allocation.

Signed-off-by: default avatarSergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
parent cde513fd

Documentation/userspace-api/media/v4l/buffer.rst

+38 −2
Original line number Diff line number Diff line
@@ -676,8 +676,6 @@ Buffer Flags 


    \normalsize



.. _memory-flags:



enum v4l2_memory

================
@@ -701,6 +699,44 @@ enum v4l2_memory 
      - 4

      - The buffer is used for :ref:`DMA shared buffer <dmabuf>` I/O.



.. _memory-flags:



Memory Consistency Flags

------------------------



.. raw:: latex



    \small



.. tabularcolumns:: |p{7.0cm}|p{2.1cm}|p{8.4cm}|



.. cssclass:: longtable



.. flat-table::

    :header-rows:  0

    :stub-columns: 0

    :widths:       3 1 4



    * .. _`V4L2-MEMORY-FLAG-NON-COHERENT`:



      - ``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



    \normalsize



Timecodes

=========

Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst

+3 −2
Original line number Diff line number Diff line
@@ -158,8 +158,9 @@ 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>`.



.. raw:: latex

include/uapi/linux/videodev2.h

+2 −0
Original line number Diff line number Diff line
@@ -962,6 +962,8 @@ struct v4l2_requestbuffers { 
	__u32			reserved[1];

};



#define V4L2_MEMORY_FLAG_NON_COHERENT			(1 << 0)



/* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */

#define V4L2_BUF_CAP_SUPPORTS_MMAP			(1 << 0)

#define V4L2_BUF_CAP_SUPPORTS_USERPTR			(1 << 1)