[RFC v4 1/8] drm: Add Enhanced Gamma LUT precision structure

[Alexandru-Cosmin Gheorghe]

Hi Uma,

On Fri, Aug 17, 2018 at 07:48:44PM +0530, Uma Shankar wrote:
> Existing LUT precision structure is having only 16 bit
> precision. This is not enough for upcoming enhanced hardwares
> and advance usecases like HDR processing. Hence added a new
> structure with 32 bit precision values. Also added the code,
> for extracting the same from values passed from userspace.
> 
> v4: Rebase
> 
> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
> ---
>  drivers/gpu/drm/drm_plane.c | 19 +++++++++++++++++++
>  include/uapi/drm/drm_mode.h | 15 +++++++++++++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 6153cbd..cd71fd0 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -430,6 +430,25 @@ void drm_plane_force_disable(struct drm_plane *plane)
>  }
>  EXPORT_SYMBOL(drm_plane_force_disable);
>  
> +/*
> + * Added to accommodate enhanced LUT precision.
> + * Max LUT precision is 32 bits.
> + */
> +uint32_t drm_color_lut_extract_ext(uint32_t user_input, uint32_t bit_precision)

You should declare this function in a header file as well.

With that fixed
Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe at arm.com>


> +{
> +	uint32_t val = user_input;
> +	uint32_t max = 0xffffffff >> (32 - bit_precision);
> +
> +	/* Round only if we're not using full precision. */
> +	if (bit_precision < 32) {
> +		val += 1UL << (32 - bit_precision - 1);
> +		val >>= 32 - bit_precision;
> +	}
> +
> +	return clamp_val(val, 0, max);
> +}
> +EXPORT_SYMBOL(drm_color_lut_extract_ext);
> +
>  /**
>   * drm_mode_plane_set_obj_prop - set the value of a property
>   * @plane: drm plane object to set property value for
> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index 8d67243..874407b 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -629,6 +629,21 @@ struct drm_color_lut {
>  	__u16 reserved;
>  };
>  
> +/*
> + * Creating 32 bit palette entries for better data
> + * precision. This will be required for HDR and
> + * similar color processing usecases.
> + */
> +struct drm_color_lut_ext {
> +	/*
> +	 * Data is U0.32 fixed point format.
> +	 */
> +	__u32 red;
> +	__u32 green;
> +	__u32 blue;
> +	__u32 reserved;
> +};
> +
>  #define DRM_MODE_PAGE_FLIP_EVENT 0x01
>  #define DRM_MODE_PAGE_FLIP_ASYNC 0x02
>  #define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
> -- 
> 1.9.1
> 
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-- 
Cheers,
Alex G