Re: [PATCH v2 2/3] drm: Add CRTC background color property (v2)

[Sean Paul <sean@poorly.run>]

On Tue, Nov 13, 2018 at 03:21:48PM -0800, Matt Roper wrote:
> Some display controllers can be programmed to present non-black colors
> for pixels not covered by any plane (or pixels covered by the
> transparent regions of higher planes).  Compositors that want a UI with
> a solid color background can potentially save memory bandwidth by
> setting the CRTC background property and using smaller planes to display
> the rest of the content.
> 
> To avoid confusion between different ways of encoding RGB data, we
> define a standard 64-bit format that should be used for this property's
> value.  Helper functions and macros are provided to generate and dissect
> values in this standard format with varying component precision values.
> 
> v2:
>  - Swap internal representation's blue and red bits to make it easier
>    to read if printed out.  (Ville)
>  - Document bgcolor property in drm_blend.c.  (Sean Paul)
>  - s/background_color/bgcolor/ for consistency between property name and
>    value storage field.  (Sean Paul)
>  - Add a convenience function to attach property to a given crtc.
> 
> Cc: dri-devel@lists.freedesktop.org
> Cc: wei.c.li@intel.com
> Cc: harish.krupo.kps@intel.com
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Sean Paul <sean@poorly.run>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic_state_helper.c |  1 +
>  drivers/gpu/drm/drm_atomic_uapi.c         |  5 +++++
>  drivers/gpu/drm/drm_blend.c               | 21 ++++++++++++++++++---
>  drivers/gpu/drm/drm_mode_config.c         |  6 ++++++
>  include/drm/drm_blend.h                   |  1 +
>  include/drm/drm_crtc.h                    | 17 +++++++++++++++++
>  include/drm/drm_mode_config.h             |  5 +++++
>  include/uapi/drm/drm_mode.h               | 26 ++++++++++++++++++++++++++
>  8 files changed, 79 insertions(+), 3 deletions(-)

/snip

> diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> index d3e0fe31efc5..7c4f902aa290 100644
> --- a/include/uapi/drm/drm_mode.h
> +++ b/include/uapi/drm/drm_mode.h
> @@ -888,6 +888,32 @@ struct drm_mode_revoke_lease {
>  	__u32 lessee_id;
>  };
>  
> +/*
> + * Put RGBA values into a standard 64-bit representation that can be used
> + * for ioctl parameters, inter-driver commmunication, etc.  If the component
> + * values being provided contain less than 16 bits of precision, they'll
> + * be shifted into the most significant bits.
> + */
> +static inline __u64
> +drm_rgba(__u8 bpc, __u16 red, __u16 green, __u16 blue, __u16 alpha)
> +{
> +	int msb_shift = 16 - bpc;
> +
> +	return (__u64)alpha << msb_shift << 48 |
> +	       (__u64)red   << msb_shift << 32 |
> +	       (__u64)green << msb_shift << 16 |
> +	       (__u64)blue  << msb_shift;
> +}
> +
> +/*
> + * Extract the specified number of bits of a specific color component from a
> + * standard 64-bit RGBA value.
> + */
> +#define DRM_RGBA_BLUE(c, numbits)  (__u16)((c & 0xFFFFull)     >> (16-numbits))
> +#define DRM_RGBA_GREEN(c, numbits) (__u16)((c & 0xFFFFull<<16) >> (32-numbits))
> +#define DRM_RGBA_RED(c, numbits)   (__u16)((c & 0xFFFFull<<32) >> (48-numbits))
> +#define DRM_RGBA_ALPHA(c, numbits) (__u16)((c & 0xFFFFull<<48) >> (64-numbits))


#define  DRM_RGBA_COMP(c, shift, numbits) \
        (__u16)(((c) & 0xFFFFull << (shift)) >> (32 - ((shift) + 16 - (numbits)))

#define DRM_RGBA_BLUE(c, numbits)  DRM_RGBA_COMP(c, 0, numbits)
#define DRM_RGBA_GREEN(c, numbits) DRM_RGBA_COMP(c, 16, numbits)
#define DRM_RGBA_RED(c, numbits)   DRM_RGBA_COMP(c, 32, numbits)
#define DRM_RGBA_ALPHA(c, numbits) DRM_RGBA_COMP(c, 48, numbits)


With that,

Reviewed-by: Sean Paul <sean@poorly.run>



> +
>  #if defined(__cplusplus)
>  }
>  #endif
> -- 
> 2.14.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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