Re: [PATCH] drm/sun4i: sun8i: Add support for pixel blend mode property

From: Maxime Ripard <maxime@cerno.tech>
To: Roman Stratiienko <r.stratiienko@gmail.com>
Cc: "Jernej Škrabec" <jernej.skrabec@gmail.com>,
	wens@csie.org, airlied@linux.ie,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Samuel Holland" <samuel@sholland.org>,
	dri-devel@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org,
	megi@xff.cz,
	"Roman Stratiienko" <roman.o.stratiienko@globallogic.com>
Subject: Re: [PATCH] drm/sun4i: sun8i: Add support for pixel blend mode property
Date: Mon, 6 Jun 2022 11:20:06 +0200	[thread overview]
Message-ID: <20220606092006.4bgxibmayv44juox@houat> (raw)
In-Reply-To: <CAGphcdniPFdqgLcpUc88ak9GzNaCvmj_TDVYTOe2bXto-Y12FQ@mail.gmail.com>

[-- Attachment #1.1: Type: text/plain, Size: 1526 bytes --]

On Mon, Jun 06, 2022 at 11:17:20AM +0300, Roman Stratiienko wrote:
> Hello Jernej,
> 
> Thank you for having a look.
> 
> вс, 5 июн. 2022 г. в 23:37, Jernej Škrabec <jernej.skrabec@gmail.com>:
> >
> > Dne nedelja, 05. junij 2022 ob 17:47:31 CEST je Roman Stratiienko napisal(a):
> > > Allwinner DE2 and DE3 hardware support 3 pixel blend modes:
> > > "None", "Pre-multiplied", "Coverage"
> > >
> > > Add the blend mode property and route it to the appropriate registers.
> > >
> > > Note:
> > > "force_premulti" parameter was added to handle multi-overlay channel
> > > cases in future changes. It must be set to true for cases when more
> > > than 1 overlay layer is used within a channel and at least one of the
> > > overlay layers within a group uses premultiplied blending mode.
> >
> > Please remove this parameter. It's nothing special, so it can be easily added
> > once it's actually needed. For now, it only complicates code.
> 
> I would prefer keeping it if you do not have any strong opinion against it.
> 
> I am working now on exposing all overlays, so it will be needed soon anyway.

KMS assumes pre-multiplied alpha anyway, so we shouldn't need a
parameter to force it: we're always going to force it.

> Also it helps to better understand the COV2PREMULT mode which has not
> the best description in the datasheet. Only after testing this
> register using devmem I became confident on its purpose.

Sounds like a good job for a comment in the source code.

Maxime

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel