[PATCH driver/intel] Allow copy_front() to fail and clean up gracefully if it does

[Egbert Eich]

Chris Wilson writes:
 > On Wed, Sep 24, 2014 at 12:34:29PM +0200, Egbert Eich wrote:
 > > 
 > > For panning one needs to be able to draw into the screen pixmap outside 
 > > of the area exposed by the crtc.
 > 
 > Note that the screen pixmap still exists and is drawn into by the
 > clients. What should happen with the panning is that the CRTC is updated
 > through set_mode_major which invalidates the new CRTC location in the big
 > screen Pixmap and the contents copied during the next shadow update.
 > 
 > That's the theory at least...

Ok, so this isn't working. I will look into this as it's easy for me
to trigger this situation.
But this still doesn't address the failing sna_create_screen_resources().

Cheers,
	Egbert.