Message-ID: <9ce1c2bd-39aa-428b-af32-6c686b897cdf@kwiboo.se>
Date: Mon, 7 Apr 2025 17:44:04 +0200
From: Jonas Karlman <jonas@...boo.se>
To: Nicolas Dufresne <nicolas.dufresne@...labora.com>,
 Hans Verkuil <hverkuil@...all.nl>
Cc: Sebastian Fricke <sebastian.fricke@...labora.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Boris Brezillon <boris.brezillon@...labora.com>,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-rockchip@...ts.infradead.org, linux-staging@...ts.linux.dev,
 Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
 Alex Bee <knaerzche@...il.com>,
 Benjamin Gaignard <benjamin.gaignard@...labora.com>,
 Detlev Casanova <detlev.casanova@...labora.com>,
 Dan Carpenter <dan.carpenter@...aro.org>,
 Christopher Obbard <christopher.obbard@...aro.org>
Subject: Re: [PATCH v7 09/12] media: rkvdec: Add get_image_fmt ops

On 2025-04-07 17:35, Nicolas Dufresne wrote:
> Le lundi 07 avril 2025 à 17:07 +0200, Jonas Karlman a écrit :
>> On 2025-04-07 16:59, Nicolas Dufresne wrote:
>>> Le lundi 07 avril 2025 à 16:17 +0200, Hans Verkuil a écrit :
>>>> On 07/04/2025 15:52, Nicolas Dufresne wrote:
>>>>> Le lundi 07 avril 2025 à 13:09 +0200, Hans Verkuil a écrit :
>>>>>> On 25/02/2025 10:40, Sebastian Fricke wrote:
>>>>>>> From: Jonas Karlman <jonas@...boo.se>
>>>>>>>
>>>>>>> Add support for a get_image_fmt() ops that returns the required image
>>>>>>> format.
>>>>>>>
>>>>>>> The CAPTURE format is reset when the required image format changes and
>>>>>>> the buffer queue is not busy.
>>>>>>>
>>>>>>> Signed-off-by: Jonas Karlman <jonas@...boo.se>
>>>>>>> Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
>>>>>>> Tested-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>
>>>>>>> Tested-by: Christopher Obbard <chris.obbard@...labora.com>
>>>>>>> ---
>>>>>>>  drivers/staging/media/rkvdec/rkvdec.c | 49 +++++++++++++++++++++++++++++++++--
>>>>>>>  drivers/staging/media/rkvdec/rkvdec.h |  2 ++
>>>>>>>  2 files changed, 49 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/staging/media/rkvdec/rkvdec.c b/drivers/staging/media/rkvdec/rkvdec.c
>>>>>>> index 70154948b4e32e2c439f259b0f1e1bbc8b52b063..5394079509305c619f1d0c1f542bfc409317c3b7 100644
>>>>>>> --- a/drivers/staging/media/rkvdec/rkvdec.c
>>>>>>> +++ b/drivers/staging/media/rkvdec/rkvdec.c
>>>>>>> @@ -111,15 +111,60 @@ static int rkvdec_try_ctrl(struct v4l2_ctrl *ctrl)
>>>>>>>  {
>>>>>>>  	struct rkvdec_ctx *ctx = container_of(ctrl->handler, struct rkvdec_ctx, ctrl_hdl);
>>>>>>>  	const struct rkvdec_coded_fmt_desc *desc = ctx->coded_fmt_desc;
>>>>>>> +	struct v4l2_pix_format_mplane *pix_mp = &ctx->decoded_fmt.fmt.pix_mp;
>>>>>>> +	enum rkvdec_image_fmt image_fmt;
>>>>>>> +	struct vb2_queue *vq;
>>>>>>> +	int ret;
>>>>>>> +
>>>>>>> +	if (desc->ops->try_ctrl) {
>>>>>>> +		ret = desc->ops->try_ctrl(ctx, ctrl);
>>>>>>> +		if (ret)
>>>>>>> +			return ret;
>>>>>>> +	}
>>>>>>> +
>>>>>>> +	if (!desc->ops->get_image_fmt)
>>>>>>> +		return 0;
>>>>>>>  
>>>>>>> -	if (desc->ops->try_ctrl)
>>>>>>> -		return desc->ops->try_ctrl(ctx, ctrl);
>>>>>>> +	image_fmt = desc->ops->get_image_fmt(ctx, ctrl);
>>>>>>> +	if (ctx->image_fmt == image_fmt)
>>>>>>> +		return 0;
>>>>>>> +
>>>>>>> +	if (rkvdec_is_valid_fmt(ctx, pix_mp->pixelformat, image_fmt))
>>>>>>> +		return 0;
>>>>>>> +
>>>>>>> +	/* format change not allowed when queue is busy */
>>>>>>> +	vq = v4l2_m2m_get_vq(ctx->fh.m2m_ctx,
>>>>>>> +			     V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE);
>>>>>>> +	if (vb2_is_busy(vq))
>>>>>>> +		return -EINVAL;
>>>>
>>>> Looking closer, this code is just wrong. It does these format change
>>>> tests for any control, so if more controls are added in the future, then
>>>> those will be checked the same way, which makes no sense.
>>>
>>> "Just wrong" should be kept for code that is semantically incorrect,
>>> just a suggestion for choice of wording.
>>>
>>>>
>>>> These tests belong to the actual control that you 'try'. In this case
>>>> rkvdec_h264_validate_sps(). This function already checks the width and
>>>> height, but it should also check the image format. It is all in the
>>>> wrong place.
>>
>> Keep in mind that rkvdec_try_ctrl and rkvdec_s_ctrl are only used for
>> CID_STATELESS_H264_SPS (and in future also CID_STATELESS_HEVC_SPS) not
>> any other control, so this is already in the correct place?
>>
>> Maybe the naming of the functions are too generic, they could be named
>> rkvdec_sps_try_ctrl and rkvdec_sps_s_ctrl or similar if that makes more
>> sense?
> 
> So we are missing that check for VP9? It will be needed for AV1 when
> rkvdec2 support gets added.

Correct, it was not needed for VP9 on rkvdec1 as it only support a
single image fmt (NV12 / YUV420_8BIT).

In the code you only see rkvdec_ctrl_ops referenced once (or possible a
second time with HEVC work-in-progress patches).

	.cfg.id = V4L2_CID_STATELESS_H264_SPS,
	.cfg.ops = &rkvdec_ctrl_ops,

Regards,
Jonas

> 
> Nicolas
> 
>>
>> Regards,
>> Jonas
>>
>>>
>>> We can do that too. Though, this was generalized since once you enable
>>> the other codecs, you endup with code duplication. I know this series
>>> is an extract from a larger one.
>>>
>>> So let's suggest to make a helper that combines rkvdec_is_valid_fmt()
>>> and the busy check. Though on that, please reply to my comment below
>>> (which you skipped).
>>>
>>>>
>>>>>>
>>>>>> This makes no sense to me. This just tries a control, and that should just
>>>>>> work, regardless of vb2_is_busy(). It's a 'try', so you are not actually
>>>>>> changing anything.
>>>>>
>>>>> See comment below, notice that this code is only reached if the control
>>>>> introduce parameters that are not compatible with the current capture
>>>>> queue fmt. The entire function uses "success" early exit, so the
>>>>> further down you get in the function, the less likely your control is
>>>>> valid.
>>>>>
>>>>>>
>>>>>>> +
>>>>>>> +	return 0;
>>>>>>> +}
>>>>>>> +
>>>>>>> +static int rkvdec_s_ctrl(struct v4l2_ctrl *ctrl)
>>>>>>> +{
>>>>
>>>> If there is a try_ctrl op specified, then the control framework
>>>> will call that first before calling s_ctrl. So any validation that
>>>> try_ctrl did does not need to be done again in s_ctrl.
>>>>
>>>> The same comment with try_ctrl is valid here as well: if there are
>>>> image format checks that need to be done, then those need to be done
>>>> per control and not as a generic check. If new controls are added in
>>>> the future, then you don't want the same checks to apply to the new
>>>> controls as well.
>>>
>>> I don't think the behaviour of try_ctrl and that being embedded in set
>>> calls was being questioned by anyone. Can you reply to the last
>>> paragraph below ?
>>>
>>>>
>>>> Regards,
>>>>
>>>> 	Hans
>>>>
>>>>>>> +	struct rkvdec_ctx *ctx = container_of(ctrl->handler, struct rkvdec_ctx, ctrl_hdl);
>>>>>>> +	const struct rkvdec_coded_fmt_desc *desc = ctx->coded_fmt_desc;
>>>>>>> +	struct v4l2_pix_format_mplane *pix_mp = &ctx->decoded_fmt.fmt.pix_mp;
>>>>>>> +	enum rkvdec_image_fmt image_fmt;
>>>>>>> +
>>>>>>> +	if (!desc->ops->get_image_fmt)
>>>>>>> +		return 0;
>>>>>>> +
>>>>>>> +	image_fmt = desc->ops->get_image_fmt(ctx, ctrl);
>>>>>>> +	if (ctx->image_fmt == image_fmt)
>>>>>>> +		return 0;
>>>>>>
>>>>>> If you really can't set a control when the queue is busy, then that should
>>>>>> be tested here, not in try_ctrl. And then you return -EBUSY.
>>>>>>
>>>>>> Am I missing something here?
>>>>>
>>>>> When I reviewed, I had imagine that s_ctrl on a request would just run
>>>>> a try. Now that I read that more careful, I see that it does a true set
>>>>> on separate copy. So yes, this can safely be moved here.
>>>>>
>>>>> Since you seem wondering "If you really can't set a control", let me
>>>>> explain what Jonas wants to protect against. RKVdec does not have any
>>>>> color conversion code, the header compound control (which header
>>>>> depends on the codec), contains details such as sub-sampling and color
>>>>> depth. Without color conversion, when the image format is locked (the
>>>>> busy queue), you can't request the HW to decode a frame witch does not
>>>>> fit. This could otherwise lead to buffer overflow in the HW,
>>>>> fortunately protected by the iommu, but you don't really want to depend
>>>>> on the mmu.
>>>>>
>>>>> I've never used try_ctrl in my decade of v4l2, so obviously, now that I
>>>>> know that s_ctrl on request is not a try, I'm fine with rejecting this
>>>>> PR, sending a new version and making a PR again. But if I was to use
>>>>> this API in userspace, my intuitive expectation would be that this
>>>>> should fail try(), even if its very rarely valid to check the queue
>>>>> state in try control.
>>>
>>> Here, since we seem to disagree on the behaviour try should have for
>>> this specific validation. What you asked on first pass is to make it so
>>> that TRY will succeed, and SET will fail. I don't really like that
>>> suggestion.
>>>
>>> Nicolas
>>>
>>>>>
>>>>> Nicolas
>>>>>
>>>>>>
>>>>>> Regards,
>>>>>>
>>>>>> 	Hans
>>>>>>
>>>>>>> +
>>>>>>> +	ctx->image_fmt = image_fmt;
>>>>>>> +	if (!rkvdec_is_valid_fmt(ctx, pix_mp->pixelformat, ctx->image_fmt))
>>>>>>> +		rkvdec_reset_decoded_fmt(ctx);
>>>>>>>  
>>>>>>>  	return 0;
>>>>>>>  }
>>>>>>>  
>>>>>>>  static const struct v4l2_ctrl_ops rkvdec_ctrl_ops = {
>>>>>>>  	.try_ctrl = rkvdec_try_ctrl,
>>>>>>> +	.s_ctrl = rkvdec_s_ctrl,
>>>>>>>  };
>>>>>>>  
>>>>>>>  static const struct rkvdec_ctrl_desc rkvdec_h264_ctrl_descs[] = {
>>>>>>> diff --git a/drivers/staging/media/rkvdec/rkvdec.h b/drivers/staging/media/rkvdec/rkvdec.h
>>>>>>> index 6f8cf50c5d99aad2f52e321f54f3ca17166ddf98..e466a2753ccfc13738e0a672bc578e521af2c3f2 100644
>>>>>>> --- a/drivers/staging/media/rkvdec/rkvdec.h
>>>>>>> +++ b/drivers/staging/media/rkvdec/rkvdec.h
>>>>>>> @@ -73,6 +73,8 @@ struct rkvdec_coded_fmt_ops {
>>>>>>>  		     struct vb2_v4l2_buffer *dst_buf,
>>>>>>>  		     enum vb2_buffer_state result);
>>>>>>>  	int (*try_ctrl)(struct rkvdec_ctx *ctx, struct v4l2_ctrl *ctrl);
>>>>>>> +	enum rkvdec_image_fmt (*get_image_fmt)(struct rkvdec_ctx *ctx,
>>>>>>> +					       struct v4l2_ctrl *ctrl);
>>>>>>>  };
>>>>>>>  
>>>>>>>  enum rkvdec_image_fmt {
>>>>>>>
>>>>>
>>>
> 

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