RandR 1.4 support for Southern Islands and ShadowFB fallback

Michel Dänzer michel at daenzer.net
Mon Apr 28 02:18:44 PDT 2014

On 26.04.2014 00:53, Ivan Drobyshevskyi wrote:
> In RADEONPreInitAccel_KMS() there's a fallback to shadowfb for recent
> chips ("info->ChipFamily >= CHIP_FAMILY_TAHITI") that that sets
> r600_shadow_fb to TRUE.

That only applies if glamor is not available. Acceleration requires
glamor as of Southern Islands.

> In RADEONScreenInit_KMS() directRenderingEnabled is not set in case
> r600_shadow_fb is set, therefore in RADEONAccelInit() nothing is done
> and SharePixmapBacking() callback is not initialized.
> Then when I try to enable my virtual display in system settings X
> crashes in SharePixmapBacking() when trying to dereference NULL
> master->SharePixmapBacking().

I guess nobody's put in the effort to make pixmap sharing work without
acceleration, or to at least make it fail more gracefully.

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

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