linux-kernel - Re: [PATCH v5 09/17] media: uapi: HEVC: Define V4L2_CID_STATELESS_HEVC_SLICE

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Message-ID: <8c13a489-323b-79cf-2bb0-920e5a4e99e0@collabora.com>
Date:   Thu, 14 Apr 2022 11:06:39 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        mchehab@...nel.org, hverkuil@...all.nl,
        ezequiel@...guardiasur.com.ar, p.zabel@...gutronix.de,
        gregkh@...uxfoundation.org, mripard@...nel.org,
        paul.kocialkowski@...tlin.com, wens@...e.org,
        jernej.skrabec@...il.com, samuel@...lland.org
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        sebastian.fricke@...labora.com
Subject: Re: [PATCH v5 09/17] media: uapi: HEVC: Define
 V4L2_CID_STATELESS_HEVC_SLICE_PARAMS as a dynamic array


Le 08/04/2022 à 20:53, Nicolas Dufresne a écrit :
> Le jeudi 07 avril 2022 à 17:29 +0200, Benjamin Gaignard a écrit :
>> Make explicit that V4L2_CID_STATELESS_HEVC_SLICE_PARAMS control is
>> a dynamic array control type.
>> Some drivers may be able to receive multiple slices in one control
>> to improve decoding performance.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>> ---
>>   Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 2 ++
>>   include/media/hevc-ctrls.h                                | 3 +++
>>   2 files changed, 5 insertions(+)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> index 7fcc6c2bac4c..1aaf3b84b584 100644
>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> @@ -2964,6 +2964,8 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>       These bitstream parameters are defined according to :ref:`hevc`.
>>       They are described in section 7.4.7 "General slice segment header
>>       semantics" of the specification.
>> +    This control is a dynamically sized 1-dimensional array,
>> +    V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
>>   
>>   .. c:type:: v4l2_ctrl_hevc_slice_params
>>   
>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>> index 96a9b71d1def..28049e1a8a07 100644
>> --- a/include/media/hevc-ctrls.h
>> +++ b/include/media/hevc-ctrls.h
>> @@ -314,6 +314,9 @@ struct v4l2_hevc_pred_weight_table {
>>   /**
>>    * v4l2_ctrl_hevc_slice_params - HEVC slice parameters
>>    *
>> + * This control is a dynamically sized 1-dimensional array,
>> + * V4L2_CTRL_FLAG_DYNAMIC_ARRAY flag must be set when using it.
>> + *
> I'm not sure about this comment, but I'm sure you forgot:
>
>
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -1505,6 +1505,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum
> v4l2_ctrl_type *type,
>                  break;
>          case V4L2_CID_STATELESS_HEVC_SLICE_PARAMS:
>                  *type = V4L2_CTRL_TYPE_HEVC_SLICE_PARAMS;
> +               *flags |= V4L2_CTRL_FLAG_DYNAMIC_ARRAY;
>                  break;
>          case V4L2_CID_STATELESS_HEVC_SCALING_MATRIX:
>                  *type = V4L2_CTRL_TYPE_HEVC_SCALING_MATRIX;
>
> Also, in AV1 we have V4L2_AV1_MAX_TILE_COUNT, which can be used in cfg.dims,
> something the driver will actually set. We could have
>
> #define V4L2_HEVC_MAX_TILE_COUNT 600
>
> And drives can set:
>
>     .dims = { V4L2_HEVC_MAX_TILE_COUNT },
>
> In the control config.

Ok that will be in v6

>
>>    * @bit_size: size (in bits) of the current slice data
>>    * @data_bit_offset: offset (in bits) to the video data in the current slice data
>>    * @nal_unit_type: specifies the coding type of the slice (B, P or I)