linux-kernel - Re: [PATCH 1/2] media: hevc: Remove RPS named flags

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Message-ID: <fdf6417e-09cd-f0a0-a351-fccd64bfc8c7@collabora.com>
Date:   Tue, 31 Aug 2021 13:56:36 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...labora.com>
To:     John Cox <jc@...esim.co.uk>
Cc:     mchehab@...nel.org, 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,
        ezequiel@...guardiasur.com.ar, 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
Subject: Re: [PATCH 1/2] media: hevc: Remove RPS named flags


Le 31/08/2021 à 13:08, John Cox a écrit :
>> Marking a picture as long-term reference is valid for DPB but not for RPS.
>> Change flag name to match with it description in HEVC spec chapiter
>> "8.3.2 Decoding process for reference picture set".
>> Remove the other unused RPS flags.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
>> ---
>> Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 6 ++----
>> drivers/staging/media/hantro/hantro_g2_hevc_dec.c         | 2 +-
>> drivers/staging/media/sunxi/cedrus/cedrus_h265.c          | 2 +-
>> include/media/hevc-ctrls.h                                | 4 +---
>> 4 files changed, 5 insertions(+), 9 deletions(-)
>>
>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> index 3865acb9e0fd..eff33c511090 100644
>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>> @@ -3138,10 +3138,8 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>> 	:c:type:`timeval` in struct :c:type:`v4l2_buffer` to a __u64.
>>      * - __u8
>>        - ``rps``
>> -      - The reference set for the reference frame
>> -        (V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_BEFORE,
>> -        V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_AFTER or
>> -        V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>> +      - Long term flag for the reference frame
>> +        (V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>>      * - __u8
>>        - ``field_pic``
>>        - Whether the reference is a field picture or a frame.
> If you are going to remove all the RPS values except for Long Term
> wouldn't it be better to rename the field too, either to "flags" or a
> bool "is_long_term"?  If we have a field called RPS it really should be
> able to have a value for any of the 5 valid Reference Picture Sets that
> a DPB entry can belong to.

I will send a v2 and rename rps into flags.

>
> As a side note, it is important to my code that the DPB array contains
> all the DPB entries not just the ones that are in use in this frame.  I
> need them so I can track which frames have left the DPB so I can
> reuse/free the MV tables associated with them (yes I could keep one for
> every entry in the capture Q but that is generally wasteful on memory
> and the Pi is often memory constrained). So maybe update the docn on DPB
> to make this explicit please? (I suspect that current code does this
> anyway as it is generally easier to do than to not.)

That should be in another patch :-)

Benjamin

>
> John Cox
>
>> diff --git a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>> index 9ea864ca5625..be46b3c28b17 100644
>> --- a/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>> +++ b/drivers/staging/media/hantro/hantro_g2_hevc_dec.c
>> @@ -503,7 +503,7 @@ static int set_ref(struct hantro_ctx *ctx)
>> 		compress_luma_addr = luma_addr + compress_luma_offset;
>> 		compress_chroma_addr = luma_addr + compress_chroma_offset;
>>
>> -		if (dpb[i].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>> +		if (dpb[i].rps == V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>> 			dpb_longterm_e |= BIT(V4L2_HEVC_DPB_ENTRIES_NUM_MAX - 1 - i);
>>
>> 		/*
>> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> index ef0311a16d01..6086cc35e8cc 100644
>> --- a/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> +++ b/drivers/staging/media/sunxi/cedrus/cedrus_h265.c
>> @@ -169,7 +169,7 @@ static void cedrus_h265_ref_pic_list_write(struct cedrus_dev *dev,
>> 		unsigned int index = list[i];
>> 		u8 value = list[i];
>>
>> -		if (dpb[index].rps == V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR)
>> +		if (dpb[index].rps == V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE)
>> 			value |= VE_DEC_H265_SRAM_REF_PIC_LIST_LT_REF;
>>
>> 		/* Each SRAM word gathers up to 4 references. */
>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>> index ef63bc205756..f587448ef495 100644
>> --- a/include/media/hevc-ctrls.h
>> +++ b/include/media/hevc-ctrls.h
>> @@ -127,9 +127,7 @@ struct v4l2_ctrl_hevc_pps {
>> 	__u64	flags;
>> };
>>
>> -#define V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_BEFORE	0x01
>> -#define V4L2_HEVC_DPB_ENTRY_RPS_ST_CURR_AFTER	0x02
>> -#define V4L2_HEVC_DPB_ENTRY_RPS_LT_CURR		0x03
>> +#define V4L2_HEVC_DPB_ENTRY_LONG_TERM_REFERENCE	0x01
>>
>> #define V4L2_HEVC_DPB_ENTRIES_NUM_MAX		16
>>