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

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Message-ID: <20260206110901.660cf712@eldfell>
Date: Fri, 6 Feb 2026 11:09:01 +0200
From: Pekka Paalanen <pekka.paalanen@...labora.com>
To: Harry Wentland <harry.wentland@....com>
Cc: Shengyu Qu <wiagn233@...look.com>, "Nícolas F. R. A.
 Prado" <nfraprado@...labora.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, 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?

The "HLG EOTF" is probably a good example of that, referring to the
reply I just sent on the patch adding "HLG" as a curve.

Thanks,
pq

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