From 670cb8f8a797b5365eafe4bc4676b4a0aaf22995 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Sat, 20 Jul 2024 12:46:51 +0200 Subject: Documentation: media: move Memory Consistency Flags The documentation of the Memory Consistency Flags was part of the struct v4l2_buffer documentation, but that struct doesn't use those flags. Instead it is used by VIDIOC_CREATE_BUFS and VIDIOC_REQBUFS. Move the documentation from buffer.rst to vidioc-reqbufs.rst which is where it belongs. Signed-off-by: Hans Verkuil --- Documentation/userspace-api/media/v4l/buffer.rst | 35 ---------------------- .../userspace-api/media/v4l/vidioc-reqbufs.rst | 33 +++++++++++++++----- 2 files changed, 25 insertions(+), 43 deletions(-) (limited to 'Documentation/userspace-api') diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst index 52bbee81c080..856874341882 100644 --- a/Documentation/userspace-api/media/v4l/buffer.rst +++ b/Documentation/userspace-api/media/v4l/buffer.rst @@ -694,41 +694,6 @@ enum v4l2_memory - 4 - The buffer is used for :ref:`DMA shared buffer ` 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 ` I/O and the - queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS - ` capability. - .. raw:: latex \normalsize diff --git a/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst b/Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst index 489e7748f98c..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 @@ -123,14 +125,6 @@ aborting or finishing any DMA in progress, an implicit .. _V4L2-BUF-CAP-SUPPORTS-MAX-NUM-BUFFERS: .. _V4L2-BUF-CAP-SUPPORTS-REMOVE-BUFS: -.. raw:: latex - - \footnotesize - -.. tabularcolumns:: |p{8.1cm}|p{2.2cm}|p{7.0cm}| - -.. cssclass:: longtable - .. flat-table:: V4L2 Buffer Capabilities Flags :header-rows: 0 :stub-columns: 0 @@ -174,6 +168,29 @@ aborting or finishing any DMA in progress, an implicit - 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 ` I/O and the + queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS + ` capability. + .. raw:: latex \normalsize -- cgit v1.2.3