[PATCH xserver] xfree86: fix gamma compute when palette_size > 256

[Michel Dänzer]

On 01/11/17 02:20 AM, Yu, Qiang wrote:
> Aaron, Michel, thanks for your comments which make me get more clear about
> the notation involved in this patch. As my understanding so far:
> 1. the crtc->gamma_size should be a hardware setting that reflect the hardware
>     capability of max gamma CLUT size
> 2. the palette_size can be bigger than crtc->gamma_size, [...]

Can it really? In Aaron's example, both have 1024 entries.


> So according to the above understanding, I think there're two solution to the problem:
> 1. DDX is responsible for setting crtc->gamma_size to max hardware capable gamma
>     CLUT size, and this patch is still needed for situation like Aaron described (11bit color
>     but 10bit gamma CLUT) and old amdgpu KMS driver that can only support 256 gamma
>     CLUT but need 10bit color.

If amdgpu only programs 256 gamma CLUT entries, does the hardware
actually interpolate the missing entries as described by Aaron? Does
this allow displaying gradients without banding, whereas the same
gradients show banding at depth 24?


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer