Re: [PATCH v3 2/4] media: mali-c55: Implement CCM block validation

[Vincenzo Frascino <vincenzo.frascino@arm.com>]

Hi Jacopo,

thank you for your patch.

On 27/06/2026 15:29, Jacopo Mondi wrote:
> From: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
> 
> Implement validation of CCM block parameters.
> 
> CCM coefficients are expressed as 13 bits signed Q4.8 format and their
> raw value cannot be higher than 8191 (BIT(13) - 1).
> 
> CCM gains are expressed as unsigned 12 bits Q4.8 format and their raw
> value cannot be higher than 4095 (BIT(12) - 1).
> 
> CCM offsets are 12 bits unsigned integers and their value cannot be
> higher than 4095 (BIT(12) - 1).
> 
> Validate the parameters provided by userspace using the .block_validate
> callback of struct v4l2_isp_params_block_type_info.
> 
> Signed-off-by: Jacopo Mondi <jacopo.mondi+renesas@ideasonboard.com>
>

I have a couple of comments. With this:

Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>

> ---
> v3:
> - new patch
> ---
>  .../media/platform/arm/mali-c55/mali-c55-params.c  | 36 ++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/media/platform/arm/mali-c55/mali-c55-params.c b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> index 0da5215c52c3..333e66ee3923 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> @@ -477,6 +477,41 @@ static const mali_c55_params_handler mali_c55_params_handlers[] = {
>  	[MALI_C55_PARAM_BLOCK_CCM] = &mali_c55_params_ccm,
>  };
>  
> +static int mali_c55_ccm_validate(struct device *dev,
> +				 const struct v4l2_isp_block_header *block)
> +{
> +	const struct mali_c55_params_ccm *ccm =
> +		(const struct mali_c55_params_ccm *)(block);
> +
> +	for (unsigned int i = 0; i < 3; i++) {
> +

Nit: extra blank line after the for opening brace, kernel style usually avoids this.

> +		for (unsigned int j = 0; j < 3; j++) {
> +			/* Coefficients are 13 bits signed Q4.8. */
> +			if (ccm->coeffs[i][j] > 8191) {

No magic numbers please :) Maybe use GENMASK(12, 0) or BIT(13) - 1 for
readability and consistency with the commit message, and similarly GENMASK(11,
0) or BIT(12) - 1 for gains and offsets. This also avoids magic numbers in
validation. The same could be applied to the other cases in this patch.

> +				dev_dbg(dev, "Invalid ccm coefficient %u\n",
> +					ccm->coeffs[i][j]);
> +				return -EINVAL;
> +			}
> +		}
> +
> +		/* Gains are 12 bits unsigned Q4.8. */
> +		if (ccm->gains[i] > 4095) {
> +			dev_dbg(dev, "Invalid ccm gain %u\n",
> +				ccm->gains[i]);
> +			return -EINVAL;
> +		}
> +
> +		/* Offsets are 12 bits unsigned integers. */
> +		if (ccm->offs[i] > 4095) {
> +			dev_dbg(dev, "Invalid ccm offset %u\n",
> +				ccm->offs[i]);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct v4l2_isp_params_block_type_info
>  mali_c55_params_block_types_info[] = {
>  	[MALI_C55_PARAM_BLOCK_SENSOR_OFFS] = {
> @@ -514,6 +549,7 @@ mali_c55_params_block_types_info[] = {
>  	},
>  	[MALI_C55_PARAM_BLOCK_CCM] = {
>  		.size = sizeof(struct mali_c55_params_ccm),
> +		.block_validate = mali_c55_ccm_validate,
>  	},
>  };
>  
> 

-- 
Regards,
Vincenzo