linux-kernel - Re: [PATCH v6 2/6] media: venus: vdec: Clamp parm smaller than 1fps and bigger than 240.

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Message-ID: <dbbf8b29-0ef4-8ebe-9fd3-c4b2f9c57b29@quicinc.com>
Date: Mon, 16 Jun 2025 21:14:27 +0530
From: Vikash Garodia <quic_vgarodia@...cinc.com>
To: Ricardo Ribalda <ribalda@...omium.org>
CC: Mauro Carvalho Chehab <mchehab@...nel.org>,
        Stanimir Varbanov
	<stanimir.k.varbanov@...il.com>,
        Bryan O'Donoghue
	<bryan.odonoghue@...aro.org>,
        Hans Verkuil <hverkuil@...all.nl>, <linux-media@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v6 2/6] media: venus: vdec: Clamp parm smaller than 1fps
 and bigger than 240.


On 6/16/2025 5:14 PM, Ricardo Ribalda wrote:
> Hi Vikash
> 
> On Mon, 16 Jun 2025 at 13:04, Vikash Garodia <quic_vgarodia@...cinc.com> wrote:
>>
>>
>> On 1/11/2025 3:25 PM, Ricardo Ribalda wrote:
>>> The driver uses "whole" fps in all its calculations (e.g. in
>>> load_per_instance()). Those calculation expect an fps bigger than 1, and
>>> not big enough to overflow.
>>>
>>> Clamp the value if the user provides a parm that will result in an invalid
>>> fps.
>>>
>>> Reported-by: Hans Verkuil <hverkuil@...all.nl>
>>> Closes: https://lore.kernel.org/linux-media/f11653a7-bc49-48cd-9cdb-1659147453e4@xs4all.nl/T/#m91cd962ac942834654f94c92206e2f85ff7d97f0
>>> Fixes: 7472c1c69138 ("[media] media: venus: vdec: add video decoder files")
>>> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>>> ---
>>>  drivers/media/platform/qcom/venus/core.h | 2 ++
>>>  drivers/media/platform/qcom/venus/vdec.c | 5 ++---
>>>  2 files changed, 4 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/qcom/venus/core.h b/drivers/media/platform/qcom/venus/core.h
>>> index 44f1c3bc4186..afae2b9fdaf7 100644
>>> --- a/drivers/media/platform/qcom/venus/core.h
>>> +++ b/drivers/media/platform/qcom/venus/core.h
>>> @@ -28,6 +28,8 @@
>>>  #define VIDC_RESETS_NUM_MAX          2
>>>  #define VIDC_MAX_HIER_CODING_LAYER 6
>>>
>>> +#define VENUS_MAX_FPS                        240
>>> +
>>>  extern int venus_fw_debug;
>>>
>>>  struct freq_tbl {
>>> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
>>> index 98c22b9f9372..c1d5f94e16b4 100644
>>> --- a/drivers/media/platform/qcom/venus/vdec.c
>>> +++ b/drivers/media/platform/qcom/venus/vdec.c
>>> @@ -481,11 +481,10 @@ static int vdec_s_parm(struct file *file, void *fh, struct v4l2_streamparm *a)
>>>       us_per_frame = timeperframe->numerator * (u64)USEC_PER_SEC;
>>>       do_div(us_per_frame, timeperframe->denominator);
>>>
>>> -     if (!us_per_frame)
>>> -             return -EINVAL;
>>> -
>>> +     us_per_frame = max(USEC_PER_SEC, us_per_frame);
>> This logic changes the actual fps from client. Consider a regular encode usecase
>> from client setting an fps as 30. The "max(USEC_PER_SEC, us_per_frame)" would
>> override it to USEC_PER_SEC and then the subsequent logic would eventually make
>> fps to 1.
>> Please make it conditional to handle the 0 fps case, i guess that the objective
>> in above code, something like below
>> if (!us_per_frame)
>>   us_per_frame = USEC_PER_SEC;
> 
> You are correct. Thanks for catching it!
> 
> I think I prefer:
> us_per_frame = clamp(us_per_frame, 1, USEC_PER_SEC);
This is good.

Regards,
Vikash
> 
> Regards
> 
> 
> 
>>
>> Regards,
>> Vikash
>>>       fps = (u64)USEC_PER_SEC;
>>>       do_div(fps, us_per_frame);
>>> +     fps = min(VENUS_MAX_FPS, fps);
>>>
>>>       inst->fps = fps;
>>>       inst->timeperframe = *timeperframe;
>>>
> 
> 
> 
> --
> Ricardo Ribalda