linux-kernel - Re: [PATCH 00/11] Plane Color Pipeline support for MediaTek

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Message-ID: <5963bca37996fa054ad75d4e5017d9c7e5158e9f.camel@collabora.com>
Date: Fri, 06 Feb 2026 08:28:14 -0500
From: Nícolas "F. R. A. Prado" <nfraprado@...labora.com>
To: Pekka Paalanen <pekka.paalanen@...labora.com>, Harry Wentland
	 <harry.wentland@....com>
Cc: Shengyu Qu <wiagn233@...look.com>, Maarten Lankhorst	
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>,  Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>, Matthias Brugger	
 <matthias.bgg@...il.com>, AngeloGioacchino Del Regno	
 <angelogioacchino.delregno@...labora.com>, dri-devel@...ts.freedesktop.org,
 	linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, daniels@...labora.com, 
	ariel.dalessandro@...labora.com, kernel@...labora.com, xaver.hugl@...il.com
Subject: Re: [PATCH 00/11] Plane Color Pipeline support for MediaTek

On Fri, 2026-02-06 at 11:09 +0200, Pekka Paalanen wrote:
> On Fri, 2 Jan 2026 13:40:21 -0500
> Harry Wentland <harry.wentland@....com> wrote:
> 
> > On 2026-01-01 07:37, Shengyu Qu wrote:
> > > 
> > > 
> > > 在 2025/12/30 02:53, Shengyu Qu 写道:  
> > > > 
> > > > 
> > > > 在 2025/12/24 3:44, NÃ colas F. R. A. Prado 写道:  
> 
> > > > > Given the lack of support for writeback connectors on the
> > > > > MediaTek KMS driver, combined with limited hardware
> > > > > documentation, I haven't been able to verify the correctness
> > > > > of
> > > > > each curve, only that they were visually sane (gamma curves
> > > > > made
> > > > > the image on the display brighter, while inverse gamma made
> > > > > it
> > > > > darker).  
> > > > 
> > > > Hmmm I don't think this is acceptable. sRGB/scRGB has two
> > > > transfer
> > > > functions mentioned in original specification[1]. To keep color
> > > > accuracy, we need someone from mediatek confirm whether this is
> > > > piece- wise or pure power 2.2 transfer function, this is
> > > > already
> > > > done in original amdgpu color pipeline series, sRGB means
> > > > piece-wise while also dedicated power 2.2 function exists.  
> > 
> > Not sure what you mean with this not being acceptable. This is
> > about
> > enabling HW support for this functionality. Not every HW has
> > writeback for testing. At some point you'll have to trust the
> > driver
> > devs if you're going to use functionality of the driver. We're not
> > always going to get everything perfect, but if that's really such a
> > worry you can always use shaders to do precisely what you want.
> > 
> 
> Hi Harry,
> 
> yes, but I understood that in this case, the hardware documentation
> available is so vague that it's impossible to say what it will
> actually
> do. There are no formulas given or referenced in the documentation,
> are
> there, Nícolas?

No formulas at all, the only documentation I had available for the
curves was the register definition, which simply lists the possible
values: SCRGB, BT709, BT2020, HLG.

-- 
Thanks,

Nícolas