Commit ac53503e authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Mauro Carvalho Chehab
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media: videobuf2: add V4L2_FLAG_MEMORY_NON_CONSISTENT flag 



By setting or clearing V4L2_FLAG_MEMORY_NON_CONSISTENT flag
user-space should be able to set or clear queue's NON_CONSISTENT
->dma_attrs. Queue's ->dma_attrs are passed to the underlying
allocator in __vb2_buf_mem_alloc(), so thus user-space is able
to request vb2 buffer's memory to be either consistent (coherent)
or non-consistent.

The patch set also adds a corresponding capability flag:
fill_buf_caps() reports V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
when queue supports user-space cache management hints. Note,
however, that MMAP_CACHE_HINTS capability only valid when the
queue is used for memory MMAP-ed streaming I/O.

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 f5f5fa73

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

+38 −2
Original line number Diff line number Diff line
@@ -577,7 +577,10 @@ Buffer Flags 
	applications shall use this flag if the data captured in the

	buffer is not going to be touched by the CPU, instead the buffer

	will, probably, be passed on to a DMA-capable hardware unit for

	further processing or output.

	further processing or output. This flag is ignored unless the

	queue is used for :ref:`memory mapping <mmap>` streaming I/O and

	reports :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS

	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.

    * .. _`V4L2-BUF-FLAG-NO-CACHE-CLEAN`:



      - ``V4L2_BUF_FLAG_NO_CACHE_CLEAN``
@@ -585,7 +588,10 @@ Buffer Flags 
      - Caches do not have to be cleaned for this buffer. Typically

	applications shall use this flag for output buffers if the data in

	this buffer has not been created by the CPU but by some

	DMA-capable unit, in which case caches have not been used.

	DMA-capable unit, in which case caches have not been used. This flag

	is ignored unless the queue is used for :ref:`memory mapping <mmap>`

	streaming I/O and reports :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS

	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.

    * .. _`V4L2-BUF-FLAG-M2M-HOLD-CAPTURE-BUF`:



      - ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF``
@@ -681,6 +687,36 @@ Buffer Flags 


    \normalsize



.. _memory-flags:



Memory Consistency Flags

========================



.. tabularcolumns:: |p{7.0cm}|p{2.2cm}|p{8.3cm}|



.. cssclass:: longtable



.. flat-table::

    :header-rows:  0

    :stub-columns: 0

    :widths:       3 1 4



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



      - ``V4L2_FLAG_MEMORY_NON_CONSISTENT``

      - 0x00000001

      - A buffer is allocated either in consistent (it will be automatically

	coherent between the CPU and the bus) or non-consistent 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-consistent 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.



.. c:type:: v4l2_memory

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

+10 −0
Original line number Diff line number Diff line
@@ -126,6 +126,7 @@ aborting or finishing any DMA in progress, an implicit 
.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:

.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:

.. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:

.. _V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS:



.. cssclass:: longtable
@@ -156,6 +157,15 @@ aborting or finishing any DMA in progress, an implicit 
      - Only valid for stateless decoders. If set, then userspace can set the

        ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the

	capture buffer until the OUTPUT timestamp changes.

    * - ``V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS``

      - 0x00000040

      - 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_FLAG_MEMORY_NON_CONSISTENT <V4L2-FLAG-MEMORY-NON-CONSISTENT>`,

        :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>`.





Return Value

============

drivers/media/common/videobuf2/videobuf2-v4l2.c

+2 −0
Original line number Diff line number Diff line
@@ -710,6 +710,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps) 
		*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;

	if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)

		*caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;

	if (q->allow_cache_hints && q->io_modes & VB2_MMAP)

		*caps |= V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS;

#ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API

	if (q->supports_requests)

		*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;

include/uapi/linux/videodev2.h

+3 −0
Original line number Diff line number Diff line
@@ -189,6 +189,8 @@ enum v4l2_memory { 
	V4L2_MEMORY_DMABUF           = 4,

};



#define V4L2_FLAG_MEMORY_NON_CONSISTENT		(1 << 0)



/* see also http://vektor.theorem.ca/graphics/ycbcr/ */

enum v4l2_colorspace {

	/*
@@ -954,6 +956,7 @@ struct v4l2_requestbuffers { 
#define V4L2_BUF_CAP_SUPPORTS_REQUESTS			(1 << 3)

#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS		(1 << 4)

#define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF	(1 << 5)

#define V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS		(1 << 6)



/**

 * struct v4l2_plane - plane info for multi-planar buffers