[xserver, 2/2] xf86RandR12: Fix XF86VidModeSetGamma triggering a BadImplementation error

[Hans de Goede]

Hi,

On 20-09-16 03:58, Michel Dänzer wrote:
> On 17/09/16 07:00 PM, Hans De Goede wrote:
>> Commit b4e46c0444bb ("xfree86: Hook up colormaps and RandR 1.2 gamma code")
>> dropped the providing of a pScrn->ChangeGamma callback from the xf86RandR12
>> code. Leaving pScrn->ChangeGamma NULL in most cases.
>>
>> This triggers the BadImplementation error in xf86ChangeGamma() :
>>
>>     if (pScrn->ChangeGamma)
>>         return (*pScrn->ChangeGamma) (pScrn, gamma);
>>
>>     return BadImplementation;
>>
>> Which causes X-apps using XF86VidModeSetGamma to crash with a
>> X protocol error.
>>
>> This commit fixes this by re-introducing the xf86RandR12ChangeGamma
>> helper removed by the commit and adjusting it to work with the new
>> combined palette / gamma code.
>>
>> Fixes: b4e46c0444bb ("xfree86: Hook up colormaps and RandR 1.2 gamma code")
>
> I suspect you really want to fix the modesetting driver to call
> xf86HandleColormaps, so it can actually benefit from that change and
> e.g. gamma sliders in games start working.

Ok, so going through my TODO list I started looking at this,
amdgpu does:

         if (xf86_config->num_crtc) {
                 xf86DrvMsgVerb(pScrn->scrnIndex, X_INFO, AMDGPU_LOGLEVEL_DEBUG,
                                "Initializing kms color map\n");
                 if (!miCreateDefColormap(pScreen))
                         return FALSE;
                 /* all amdgpus support 10 bit CLUTs */
                 if (!xf86HandleColormaps(pScreen, 256, 10,
                                          NULL, NULL,
                                          CMAP_PALETTED_TRUECOLOR
                                          | CMAP_RELOAD_ON_MODE_SWITCH))
                         return FALSE;
         }

Which seems like it should mostly work for modesetting to,
except for the all "amdgpus support 10 bit CLUTs" part,
any ideas what to put there for modesetting, or how to
query this from the kernel driver ?

Regards,

Hans