Hi Eric, On Tue, Apr 24, 2018 at 09:53:28AM -0700, Eric Anholt wrote: > Maxime Ripard <maxime.ripard@xxxxxxxxxxx> writes: > > > The vc4 HVS uses an internal RGB888 representation of the frames, and will > > by default expand formats using a lower depth using zeros. > > > > This causes an issue when we try to use other compositing software such as > > pixman that seems to be filling the missing bits using the format least > > significant bit value. As such, this prevents us from checking the display > > output in a reliable way. > > I don't think this is the right expansion function, though? My > understanding of proper unorm expansion, and what pixman's > unorm_to_unorm() does, is that you replicate the value in the missing > bits until you've filled them all (so SCALER_CTL0_EXPAND_REPEAT) This was based on experiment, so I might have missed that case and you are probably right. I'll test with SCALER_CTL0_EXPAND_REPEAT and let you know :) Thanks! Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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