linux-kernel - Re: [PATCH v3 09/14] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT

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Message-ID: <4378293.LvFx2qVVIh@kista>
Date:   Fri, 25 Feb 2022 20:30:20 +0100
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     mchehab@...nel.org, ezequiel@...guardiasur.com.ar,
        p.zabel@...gutronix.de, gregkh@...uxfoundation.org,
        mripard@...nel.org, paul.kocialkowski@...tlin.com, wens@...e.org,
        jonas@...boo.se, nicolas@...fresne.ca,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        kernel@...labora.com, knaerzche@...il.com, jc@...esim.co.uk,
        Benjamin Gaignard <benjamin.gaignard@...labora.com>
Subject: Re: [PATCH v3 09/14] media: uapi: Add V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSET control

Hi!

Dne petek, 25. februar 2022 ob 17:45:55 CET je Benjamin Gaignard napisal(a):
> The number of 'entry point offset' could be very variable.
> Rather than use a large static array define a v4l2 dynamic array
> of integer control.

I suggest we should be more specific and say U32 (V4L2_CTRL_TYPE_U32).

> The number of entry point offsets is reported by the elems field.
> 
> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst          | 9 +++++++++
>  include/media/hevc-ctrls.h                               | 1 +
>  2 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/
Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 44a268a948c0..71f7dc1c1ccd 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -3128,6 +3128,15 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>  
>      \normalsize
>  
> +``V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS (integer)``

Here you have OFFSETS (plural) ...

> +    Specifies the i-th entry point offset in bytes and is represented by
> +    offset_len_minus1 plus 1 bits.

You probably mean entry_point_offset_minus1? offset_len_minus1 just tells how 
much bits need to be read for each element and it's not important for actual 
decoding.

> +    This control is a dynamically sized array. The number of entry point
> +    offsets is reported by the ``elems`` field.
> +    This bitstream parameter is defined according to :ref:`hevc`.
> +    They are described in section 7.4.7.1 "General slice segment header
> +    semantics" of the specification.
> +
>  ``V4L2_CID_STATELESS_HEVC_SCALING_MATRIX (struct)``
>      Specifies the HEVC scaling matrix parameters used for the scaling 
process
>      for transform coefficients.
> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
> index 3016c1abb1d0..3f8a67924df3 100644
> --- a/include/media/hevc-ctrls.h
> +++ b/include/media/hevc-ctrls.h
> @@ -20,6 +20,7 @@
>  #define V4L2_CID_STATELESS_HEVC_DECODE_PARAMS	(V4L2_CID_CODEC_BASE + 
1012)
>  #define V4L2_CID_STATELESS_HEVC_DECODE_MODE	(V4L2_CID_CODEC_BASE + 
1015)
>  #define V4L2_CID_STATELESS_HEVC_START_CODE	(V4L2_CID_CODEC_BASE + 1016)
> +#define V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSET (V4L2_CID_CODEC_BASE + 
1017)

... and here you have OFFSET (singlular). I suggest plural form to be used in 
all places, including subject line of this commit.

Additionally, it would be nice if control is initialized, like so:
https://github.com/jernejsk/linux-1/commit/
f938e162cd8dd77c9f6f1b248d80144840a37bce

Best regards,
Jernej

>  
>  /* enum v4l2_ctrl_type type values */
>  #define V4L2_CTRL_TYPE_HEVC_SPS 0x0120
> -- 
> 2.32.0
> 
>