Commit b4e46c0444 ("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: b4e46c0444 ("xfree86: Hook up colormaps and RandR 1.2 gamma code")
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>