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

[Vikash Garodia]

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@xxxxxxxxx>
> Closes: https://lore.kernel.org/linux-media/f11653a7-bc49-48cd-9cdb-1659147453e4@xxxxxxxxx/T/#m91cd962ac942834654f94c92206e2f85ff7d97f0
> Fixes: 7472c1c69138 ("[media] media: venus: vdec: add video decoder files")
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
>  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;

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;
>