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

[Ricardo Ribalda <ribalda@chromium.org>]

Hi Vikash

On Mon, 16 Jun 2025 at 13:04, Vikash Garodia <quic_vgarodia@quicinc.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@xs4all.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@chromium.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);

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