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From: Benjamin Gaignard <benjamin.gaignard@collabora.com>
To: Hans Verkuil <hverkuil-cisco@xs4all.nl>,
	ezequiel@collabora.com, p.zabel@pengutronix.de,
	mchehab@kernel.org, robh+dt@kernel.org, shawnguo@kernel.org,
	s.hauer@pengutronix.de, festevam@gmail.com, lee.jones@linaro.org,
	gregkh@linuxfoundation.org, mripard@kernel.org,
	paul.kocialkowski@bootlin.com, wens@csie.org,
	jernej.skrabec@siol.net, emil.l.velikov@gmail.com
Cc: kernel@pengutronix.de, linux-imx@nxp.com,
	linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org,
	kernel@collabora.com, cphealy@gmail.com
Subject: Re: [PATCH v10 6/9] media: uapi: Add a control for HANTRO driver
Date: Wed, 5 May 2021 17:20:46 +0200
Message-ID: <1cf94540-7f4d-0179-dd1e-0b82ee30f6d2@collabora.com> (raw)
In-Reply-To: <a7c9fe23-2900-ac90-7131-21380fbfc793@xs4all.nl>


Le 05/05/2021 à 16:55, Hans Verkuil a écrit :
> On 20/04/2021 14:10, Benjamin Gaignard wrote:
>> The HEVC HANTRO driver needs to know the number of bits to skip at
>> the beginning of the slice header.
>> That is a hardware specific requirement so create a dedicated control
>> for this purpose.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> ---
>>   .../userspace-api/media/drivers/hantro.rst    | 19 +++++++++++++++++++
>>   .../userspace-api/media/drivers/index.rst     |  1 +
>>   include/media/hevc-ctrls.h                    | 13 +++++++++++++
>>   3 files changed, 33 insertions(+)
>>   create mode 100644 Documentation/userspace-api/media/drivers/hantro.rst
>>
>> diff --git a/Documentation/userspace-api/media/drivers/hantro.rst b/Documentation/userspace-api/media/drivers/hantro.rst
>> new file mode 100644
>> index 000000000000..cd9754b4e005
>> --- /dev/null
>> +++ b/Documentation/userspace-api/media/drivers/hantro.rst
>> @@ -0,0 +1,19 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +Hantro video decoder driver
>> +===========================
>> +
>> +The Hantro video decoder driver implements the following driver-specific controls:
>> +
>> +``V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP (integer)``
>> +    Specifies to Hantro HEVC video decoder driver the number of data (in bits) to
>> +    skip in the slice segment header.
>> +    If non-IDR, the bits to be skipped go from syntax element "pic_output_flag"
>> +    to before syntax element "slice_temporal_mvp_enabled_flag".
>> +    If IDR, the skipped bits are just "pic_output_flag"
>> +    (separate_colour_plane_flag is not supported).
> I'm not very keen on this. Without this information the video data cannot be
> decoded, or will it just be suboptimal?

Without that information the video can't be decoded.

>
> The problem is that a generic decoder would have to know that the HW is a hantro,
> and then call this control. If they don't (and are testing on non-hantro HW), then
> it won't work, thus defeating the purpose of the HW independent decoder API.
>
> Since hantro is widely used, and if there is no other way to do this beside explitely
> setting this control, then perhaps this should be part of the standard HEVC API.
> Non-hantro drivers that do not need this can just skip it.

Even if I put this parameter in decode_params structure that would means that a generic
userland decoder will have to know how the compute this value for hantro HW since it
isn't something that could be done on kernel side.


Regards,
Benjamin

>
> Regards,
>
> 	Hans
>
>> +
>> +.. note::
>> +
>> +        This control is not yet part of the public kernel API and
>> +        it is expected to change.
>> diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
>> index 1a9038f5f9fa..12e3c512d718 100644
>> --- a/Documentation/userspace-api/media/drivers/index.rst
>> +++ b/Documentation/userspace-api/media/drivers/index.rst
>> @@ -33,6 +33,7 @@ For more details see the file COPYING in the source distribution of Linux.
>>   
>>   	ccs
>>   	cx2341x-uapi
>> +        hantro
>>   	imx-uapi
>>   	max2175
>>   	meye-uapi
>> diff --git a/include/media/hevc-ctrls.h b/include/media/hevc-ctrls.h
>> index 8e0109eea454..b713eeed1915 100644
>> --- a/include/media/hevc-ctrls.h
>> +++ b/include/media/hevc-ctrls.h
>> @@ -224,4 +224,17 @@ struct v4l2_ctrl_hevc_decode_params {
>>   	__u64	flags;
>>   };
>>   
>> +/*  MPEG-class control IDs specific to the Hantro driver as defined by V4L2 */
>> +#define V4L2_CID_CODEC_HANTRO_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1200)
>> +/*
>> + * V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP -
>> + * the number of data (in bits) to skip in the
>> + * slice segment header.
>> + * If non-IDR, the bits to be skipped go from syntax element "pic_output_flag"
>> + * to before syntax element "slice_temporal_mvp_enabled_flag".
>> + * If IDR, the skipped bits are just "pic_output_flag"
>> + * (separate_colour_plane_flag is not supported).
>> + */
>> +#define V4L2_CID_HANTRO_HEVC_SLICE_HEADER_SKIP	(V4L2_CID_CODEC_HANTRO_BASE + 0)
>> +
>>   #endif
>>
>

  reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-20 12:10 [PATCH v10 0/9] Add HANTRO G2/HEVC decoder support for IMX8MQ Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 1/9] media: hevc: Add fields and flags for hevc PPS Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 2/9] media: hevc: Add decode params control Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 3/9] media: hantro: change hantro_codec_ops run prototype to return errors Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 4/9] media: hantro: Define HEVC codec profiles and supported features Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 5/9] media: hantro: Only use postproc when post processed formats are defined Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 6/9] media: uapi: Add a control for HANTRO driver Benjamin Gaignard
2021-04-29 13:43   ` Ezequiel Garcia
2021-05-05 14:55   ` Hans Verkuil
2021-05-05 15:20     ` Benjamin Gaignard [this message]
2021-05-06 12:50       ` Hans Verkuil
2021-05-06 13:11         ` John Cox
2021-05-06 14:29           ` Nicolas Dufresne
2021-05-16 23:04         ` Ezequiel Garcia
2021-05-18 17:17           ` Nicolas Dufresne
2021-05-05 21:01     ` Ezequiel Garcia
2021-05-05 15:18   ` John Cox
2021-05-05 15:33     ` Nicolas Dufresne
2021-04-20 12:10 ` [PATCH v10 7/9] media: hantro: handle V4L2_PIX_FMT_HEVC_SLICE control Benjamin Gaignard
2021-04-20 12:10 ` [PATCH v10 8/9] media: hantro: Introduce G2/HEVC decoder Benjamin Gaignard
2021-05-05 14:47   ` Hans Verkuil
2021-04-20 12:10 ` [PATCH v10 9/9] media: hantro: IMX8M: add variant for G2/HEVC codec Benjamin Gaignard
2021-05-05 14:42 ` [PATCH v10 0/9] Add HANTRO G2/HEVC decoder support for IMX8MQ Hans Verkuil
2021-05-25 15:39   ` Hans Verkuil
2021-05-25 16:14     ` Benjamin Gaignard

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