Hi Hans,
On Tue, Jan 22, 2019 at 8:27 PM <hverkuil-cisco@xxxxxxxxx> wrote:
>
> From: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
>
> The "Codec Interface" chapter is poorly named since codecs are just one
> use-case of the Memory-to-Memory Interface. Rename it and clean up the
> text a bit.
>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> ---
> .../media/uapi/mediactl/request-api.rst | 4 ++--
> .../v4l/{dev-codec.rst => dev-mem2mem.rst} | 21 +++++++------------
> Documentation/media/uapi/v4l/devices.rst | 2 +-
> .../media/uapi/v4l/pixfmt-compressed.rst | 2 +-
> Documentation/media/uapi/v4l/vidioc-qbuf.rst | 2 +-
> 5 files changed, 13 insertions(+), 18 deletions(-)
> rename Documentation/media/uapi/v4l/{dev-codec.rst => dev-mem2mem.rst} (79%)
>
Thanks for this cleanup! Indeed it makes much more sense with your
changes. Some comments inline.
> diff --git a/Documentation/media/uapi/mediactl/request-api.rst b/Documentation/media/uapi/mediactl/request-api.rst
> index 4b25ad03f45a..1ad631e549fe 100644
> --- a/Documentation/media/uapi/mediactl/request-api.rst
> +++ b/Documentation/media/uapi/mediactl/request-api.rst
> @@ -91,7 +91,7 @@ A request must contain at least one buffer, otherwise ``ENOENT`` is returned.
> A queued request cannot be modified anymore.
>
> .. caution::
> - For :ref:`memory-to-memory devices <codec>` you can use requests only for
> + For :ref:`memory-to-memory devices <mem2mem>` you can use requests only for
> output buffers, not for capture buffers. Attempting to add a capture buffer
> to a request will result in an ``EACCES`` error.
>
> @@ -152,7 +152,7 @@ if it had just been allocated.
> Example for a Codec Device
> --------------------------
>
> -For use-cases such as :ref:`codecs <codec>`, the request API can be used
> +For use-cases such as :ref:`codecs <mem2mem>`, the request API can be used
I guess this should eventually be made to point to the codec sections.
Alex, perhaps it would make sense to do it in your documentation
patch.
> to associate specific controls to
> be applied by the driver for the OUTPUT buffer, allowing user-space
> to queue many such buffers in advance. It can also take advantage of requests'
> diff --git a/Documentation/media/uapi/v4l/dev-codec.rst b/Documentation/media/uapi/v4l/dev-mem2mem.rst
> similarity index 79%
> rename from Documentation/media/uapi/v4l/dev-codec.rst
> rename to Documentation/media/uapi/v4l/dev-mem2mem.rst
> index b5e017c17834..69efcc747588 100644
> --- a/Documentation/media/uapi/v4l/dev-codec.rst
> +++ b/Documentation/media/uapi/v4l/dev-mem2mem.rst
> @@ -7,11 +7,11 @@
> ..
> .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
>
> -.. _codec:
> +.. _mem2mem:
>
> -***************
> -Codec Interface
> -***************
> +********************************
> +Video Memory To Memory Interface
> +********************************
>
> A V4L2 codec can compress, decompress, transform, or otherwise convert
Codec still left here.
> video data from one format into another format, in memory. Typically
> @@ -25,19 +25,14 @@ memory) stream I/O. An application will have to setup the stream I/O for
> both sides and finally call :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
> for both capture and output to start the codec.
Ditto.
>
> -Video compression codecs use the MPEG controls to setup their codec
> -parameters
> -
> -.. note::
> -
> - The MPEG controls actually support many more codecs than
> - just MPEG. See :ref:`mpeg-controls`.
> +Video compression codecs use codec controls to setup their codec parameters.
> +See :ref:`mpeg-controls`.
>
> Memory-to-memory devices function as a shared resource: you can
> open the video node multiple times, each application setting up their
> -own codec properties that are local to the file handle, and each can use
> +own properties that are local to the file handle, and each can use
> it independently from the others. The driver will arbitrate access to
> -the codec and reprogram it whenever another file handler gets access.
> +the hardware and reprogram it whenever another file handler gets access.
> This is different from the usual video node behavior where the video
> properties are global to the device (i.e. changing something through one
> file handle is visible through another file handle).
> diff --git a/Documentation/media/uapi/v4l/devices.rst b/Documentation/media/uapi/v4l/devices.rst
> index d6fcf3db5909..07f8d047662b 100644
> --- a/Documentation/media/uapi/v4l/devices.rst
> +++ b/Documentation/media/uapi/v4l/devices.rst
> @@ -21,7 +21,7 @@ Interfaces
> dev-overlay
> dev-output
> dev-osd
> - dev-codec
> + dev-mem2mem
> dev-raw-vbi
> dev-sliced-vbi
> dev-radio
> diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> index e4c5e456df59..2675bef3eefe 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> @@ -73,7 +73,7 @@ Compressed Formats
> - 'MG2S'
> - MPEG-2 parsed slice data, as extracted from the MPEG-2 bitstream.
> This format is adapted for stateless video decoders that implement a
> - MPEG-2 pipeline (using the :ref:`codec` and :ref:`media-request-api`).
> + MPEG-2 pipeline (using the :ref:`mem2mem` and :ref:`media-request-api`).
Reference to be updated later too.
Best regards,
Tomasz
