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From: Eric Anholt <eric@anholt.net>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>,
	dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/vc4: plane: Expand the lower bits using the LSB
Date: Tue, 24 Apr 2018 09:53:28 -0700	[thread overview]
Message-ID: <87604gtuk7.fsf@anholt.net> (raw)
In-Reply-To: <20180424074814.6922-1-maxime.ripard@bootlin.com>


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Maxime Ripard <maxime.ripard@bootlin.com> 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)

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  reply	other threads:[~2018-04-24 16:53 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24  7:48 [PATCH] drm/vc4: plane: Expand the lower bits using the LSB Maxime Ripard
2018-04-24 16:53 ` Eric Anholt [this message]
2018-05-14 13:20   ` Maxime Ripard
2018-05-14 13:32 ` Stefan Schake

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