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Date: Tue, 15 Feb 2022 15:57:41 +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 15:50, John Cox a écrit :
> On Tue, 15 Feb 2022 15:35:12 +0100, you wrote:
>
>> 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 ?
> I, personally, would be in favour of making the slice header control a
> variable array just as it is. If userland can't cope with multiple
> entries then just send them one at a time and the code looks exactly
> like it does at the moment and if the driver can't then set max array
> entries to 1.
>
> Having implemented this in rpi port of ffmpeg and the RPi V4L2 driver I
> can say with experience that the code and effort overhead is very low.
>
> Either way having a multiple slice header control in the UAPI is
> important for efficiency.
Removing this field was one the Jernej's remarks.
If he agree with you it won't be a big effort for me to remove this patch
from v3.
Regards,
Benjamin
>
> Regards
>
> John Cox
>
>>>> 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;
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