linux-kernel - Re: [RFC v2 6/8] media: uapi: Remove bit_size field from v4l2_ctrl_hevc_slice

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Message-ID: <99062279-a3c4-96f7-4c4b-f39e7f812e68@collabora.com>
Date:   Tue, 15 Feb 2022 15:35:12 +0100
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     John Cox <jc@...esim.co.uk>
Cc:     mchehab@...nel.org, 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, hverkuil-cisco@...all.nl,
        jonas@...boo.se, nicolas@...fresne.ca, 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
Subject: Re: [RFC v2 6/8] media: uapi: Remove bit_size field from
 v4l2_ctrl_hevc_slice_params


Le 15/02/2022 à 15:17, John Cox a écrit :
> Hi
>
>> The bit size of the slice could be deduced from the buffer payload
>> so remove bit_size field to avoid duplicated the information.
> I think this is a bad idea. In the future we are (I hope) going to want
> to have an array (variable) of slice headers all referring to the same
> bit buffer.  When we do that we will need this field.

I wonder if that could be considering like another decode mode and so
use an other control ?

>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>> ---
>> .../userspace-api/media/v4l/ext-ctrls-codec.rst       |  3 ---
>> drivers/staging/media/sunxi/cedrus/cedrus_h265.c      | 11 ++++-------
>> include/uapi/linux/v4l2-controls.h                    |  3 +--
>> 3 files changed, 5 insertions(+), 12 deletions(-)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> index 3296ac3b9fca..c3ae97657fa7 100644
>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> @@ -2965,9 +2965,6 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>>      :stub-columns: 0
>>      :widths:       1 1 2
>>
>> -    * - __u32
>> -      - ``bit_size``
>> -      - Size (in bits) of the current slice data.
>>      * - __u32
>>        - ``data_bit_offset``
>>        - Offset (in bits) to the video data in the current slice data.
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> index 8ab2d9c6f048..db8c7475eeb8 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> @@ -312,8 +312,8 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>> 	const struct v4l2_hevc_pred_weight_table *pred_weight_table;
>> 	unsigned int width_in_ctb_luma, ctb_size_luma;
>> 	unsigned int log2_max_luma_coding_block_size;
>> +	size_t slice_bytes;
>> 	dma_addr_t src_buf_addr;
>> -	dma_addr_t src_buf_end_addr;
>> 	u32 chroma_log2_weight_denom;
>> 	u32 output_pic_list_index;
>> 	u32 pic_order_cnt[2];
>> @@ -370,8 +370,8 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>>
>> 	cedrus_write(dev, VE_DEC_H265_BITS_OFFSET, 0);
>>
>> -	reg = slice_params->bit_size;
>> -	cedrus_write(dev, VE_DEC_H265_BITS_LEN, reg);
>> +	slice_bytes = vb2_get_plane_payload(&run->src->vb2_buf, 0);
>> +	cedrus_write(dev, VE_DEC_H265_BITS_LEN, slice_bytes);
> I think one of these must be wrong. bit_size is in bits,
> vb2_get_plane_payload is in bytes?

You are right it should be vb2_get_plane_payload() * 8 to get the size in bits.

I will change that in v3.

>
> Regards
>
> John Cox
>   
>> 	/* Source beginning and end addresses. */
>>
>> @@ -384,10 +384,7 @@ static void cedrus_h265_setup(struct cedrus_ctx *ctx,
>>
>> 	cedrus_write(dev, VE_DEC_H265_BITS_ADDR, reg);
>>
>> -	src_buf_end_addr = src_buf_addr +
>> -			   DIV_ROUND_UP(slice_params->bit_size, 8);
>> -
>> -	reg = VE_DEC_H265_BITS_END_ADDR_BASE(src_buf_end_addr);
>> +	reg = VE_DEC_H265_BITS_END_ADDR_BASE(src_buf_addr + slice_bytes);
>> 	cedrus_write(dev, VE_DEC_H265_BITS_END_ADDR, reg);
>>
>> 	/* Coding tree block address */
>> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
>> index b1a3dc05f02f..27f5d272dc43 100644
>> --- a/include/uapi/linux/v4l2-controls.h
>> +++ b/include/uapi/linux/v4l2-controls.h
>> @@ -2457,7 +2457,6 @@ struct v4l2_hevc_pred_weight_table {
>> #define V4L2_HEVC_SLICE_PARAMS_FLAG_DEPENDENT_SLICE_SEGMENT	(1ULL << 9)
>>
>> struct v4l2_ctrl_hevc_slice_params {
>> -	__u32	bit_size;
>> 	__u32	data_bit_offset;
>>
>> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: NAL unit header */
>> @@ -2484,7 +2483,7 @@ struct v4l2_ctrl_hevc_slice_params {
>> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: Picture timing SEI message */
>> 	__u8	pic_struct;
>>
>> -	__u8	reserved;
>> +	__u8	reserved[5];
>>
>> 	/* ISO/IEC 23008-2, ITU-T Rec. H.265: General slice segment header */
>> 	__u32	slice_segment_addr;