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Documentation: media: move Memory Consistency Flags

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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 <hverkuil-cisco@xs4all.nl>
This commit is contained in:
Hans Verkuil 2024-07-20 12:46:51 +02:00
parent 2b9e67861b
commit 670cb8f8a7
2 changed files with 25 additions and 43 deletions
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35
Documentation/userspace-api/media/v4l/buffer.rst
View File

@ -694,41 +694,6 @@ 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

33
Documentation/userspace-api/media/v4l/vidioc-reqbufs.rst
View File

@ -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 <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