Re: [PATCH 1/5] drm: Add helpers for programming hardware gamma LUTs

[Javier Martinez Canillas <javierm@redhat.com>]

Thomas Zimmermann <tzimmermann@suse.de> writes:

> Provide helpers that program hardware gamma LUTs. Tha gamma ramp is
> either provided by the driver or generated by the helper.
>
> The DRM driver exports the GAMMA_LUT property with a fixed number of
> entries per color component, such as 256 on 8-bit-wide components. The
> entries describe the gamma ramp of each individual component. The new
> helper drm_crtc_load_gamma_888() loads such gamma ramp to hardware. The
> hardware uses each displayed pixel's individial components as indeces

I think the correct plural form is either "indexes" and "indices".

> into the hardware gamma table.
>
> For color modes with less than 8 bits per color component, the helpers
> drm_crtc_load_gamma_565_from() and drm_crtc_load_gamma_555_from_888()
> interpolate the provided gamma ramp to reduce it to the correct number
> of entries; 5/6/5 for RGB565-like formats and 5/5/5 for RGB1555-like
> formats.
>
> If no gamma ramp has been provided, drivers can use the new helper
> drm_crtc_fill_gamma_888() to load a default gamma ramp with 256 entries
> per color component. For color modes with less bits, the new helpers
> drm_crtc_fill_gamma_565() and drm_crtc_fill_gamma_555() are available.
> The default gamma ramp uses a gamma factor of 1. Later patches can
> change this. For PCs, a gamma factor of 2.2 is common.
>
> For color modes with palette, drm_crtc_load_palette_8() load an 8-bit
> palette into the hardware. If no palette has been specified,
> drm_crtc_fill_palette_8() load a system-specific default palette. This
> is currently only a grey-scale palette with increasing luminance, but
> later patches can change this. For PCs, a VGA default palette could
> be used.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/drm_color_mgmt.c | 206 +++++++++++++++++++++++++++++++
>  include/drm/drm_color_mgmt.h     |  27 ++++
>  2 files changed, 233 insertions(+)
>

Thanks a lot for adding all these helpers. I'm not an expert on gamma LUTs
but the patch looks good to me.

Acked-by: Javier Martinez Canillas <javierm@redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat