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

[Vincenzo Frascino]

Hi Jacopo,

thank you for your patch.

On 27/06/2026 15:29, Jacopo Mondi wrote:
> From: Jacopo Mondi <jacopo.mondi+renesas@xxxxxxxxxxxxxxxx>
> 
> Implement validation of Gamma block parameters.
> 
> Gamma gains are expressed as unsigned 12 bits Q4.8 format and their raw
> value cannot be higher than 4095 (BIT(12) - 1).
> 
> Gamma offsets are 12 bits unsigned integers and their value cannot be
> higher than 4095 (BIT(12) - 1).
> 
> The Gamma LUT table is expected to have 0 as first member and 0xfff
> as last member.
> 
> 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@xxxxxxxxxxxxxxxx>
> 

Looks good overall. I have just one comment. With this:

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

> ---
> v3:
> - new patch
> ---
>  .../media/platform/arm/mali-c55/mali-c55-params.c  | 34 ++++++++++++++++++++++
>  1 file changed, 34 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 5857e9c2daf7..e9ab0e2dee15 100644
> --- a/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> +++ b/drivers/media/platform/arm/mali-c55/mali-c55-params.c
> @@ -581,6 +581,38 @@ static int mali_c55_ccm_validate(struct device *dev,
>  	return 0;
>  }
>  
> +static int mali_c55_gamma_validate(struct device *dev,
> +				   const struct v4l2_isp_block_header *block)
> +{
> +	const struct mali_c55_params_gamma *gamma =
> +		(const struct mali_c55_params_gamma *)(block);
> +
> +	for (unsigned int i = 0; i < 3; i++) {
> +		/* Gains are 12 bits unsigned Q4.8. */
> +		if (gamma->gains[i] > 4095) {
> +			dev_dbg(dev, "Invalid gain value %u\n",
> +				gamma->gains[i]);
> +			return -EINVAL;
> +		}
> +
> +		/* Offsets are 12 bits unsigned integers. */
> +		if (gamma->offs[i] > 4095) {
> +			dev_dbg(dev, "Invalid offset value %u\n",
> +				gamma->offs[i]);
> +			return -EINVAL;
> +		}
> +	}
> +
> +	/* Check the first and last gamma lut entries match the expectations. */
> +	if (gamma->lut[0] != 0 ||
> +	    gamma->lut[MALI_C55_NUM_GAMMA_LUT_ELEMENTS - 1] != 0xfff) {

I am still learning about these things and might be wrong. Should not we also
validate that intermediate LUT entries are monotonic and non-decreasing?

> +		dev_dbg(dev, "Invalid Gamma LUT table\n");
> +		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] = {
> @@ -622,9 +654,11 @@ mali_c55_params_block_types_info[] = {
>  	},
>  	[MALI_C55_PARAM_BLOCK_GAMMA_FR] = {
>  		.size = sizeof(struct mali_c55_params_gamma),
> +		.block_validate = mali_c55_gamma_validate,
>  	},
>  	[MALI_C55_PARAM_BLOCK_GAMMA_DS] = {
>  		.size = sizeof(struct mali_c55_params_gamma),
> +		.block_validate = mali_c55_gamma_validate,
>  	},
>  };
>  
> 

-- 
Regards,
Vincenzo