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

[Michel Dänzer]

On 30/10/17 01:26 PM, Yu, Qiang wrote:
> 
>>> Or maybe it's better to enlarge the crtc gamma size according to randr crtc
>>> and let kernel driver to do the resize fit.
>>
>> Yes, that needs to happen anyway to make the display hardware actually
>> take advantage of 30 bits per pixel, doesn't it?
> But for randr crtc gamma size < 256, I see you don't shrink the crtc gamma
> size. Any reason?

There has traditionally been an assumption that the gamma CLUT has 256
entries. I didn't change anything about that. It also works at depth
15/16, even though in that case the hardware only actually uses a
fraction of the ramp's entries.


>>> But I see driver like amdgpu with old KMS driver only has 256 entries and the
>>> gamma set syscall won't work correctly for size>256.
>>
>> That needs to be fixed then, and the userspace driver should probably
>> only allow setting depth 30 when it knows the kernel driver can handle it.
> That's the DDX work. For amdgpu, seems we can support it in DC KMS.

Right, let's handle this in the driver, and drop this patch.


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