Re: [PATCH v9 1/8] drm/display/dsc: Add flatness and initial scale value calculations

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, May 10, 2023 at 03:54:41PM -0700, Jessica Zhang wrote:
> Add helpers to calculate det_thresh_flatness and initial_scale_value as
> these calculations are defined within the DSC spec.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
> ---
>  include/drm/display/drm_dsc_helper.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/include/drm/display/drm_dsc_helper.h b/include/drm/display/drm_dsc_helper.h
> index 0bb0c3afd740..422135a33d65 100644
> --- a/include/drm/display/drm_dsc_helper.h
> +++ b/include/drm/display/drm_dsc_helper.h
> @@ -25,5 +25,16 @@ void drm_dsc_set_rc_buf_thresh(struct drm_dsc_config *vdsc_cfg);
>  int drm_dsc_setup_rc_params(struct drm_dsc_config *vdsc_cfg, enum drm_dsc_params_kind kind);
>  int drm_dsc_compute_rc_parameters(struct drm_dsc_config *vdsc_cfg);
>  
> +static inline void drm_dsc_set_initial_scale_value(struct drm_dsc_config *dsc)
> +{
> +	dsc->initial_scale_value = 8 * dsc->rc_model_size /
> +		(dsc->rc_model_size - dsc->initial_offset);
> +}

I would suggest using pure functions whenever possible. Makes it much
easier to reason about the code when you know there are no side effects.

> +
> +static inline int drm_dsc_calculate_flatness_det_thresh(struct drm_dsc_config *dsc)

'dsc' can be const. The word "calculate" seems pretty much redundant.

> +{
> +	return 2 << (dsc->bits_per_component - 8);
> +}
> +
>  #endif /* _DRM_DSC_HELPER_H_ */
>  
> 
> -- 
> 2.40.1

-- 
Ville Syrjälä
Intel