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

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Message-ID: <CAFZQkGxdizG15chbehb-TGfBy4yL4NRy7GVD1b51mASmRG+0sA@mail.gmail.com>
Date: Wed, 7 Jan 2026 21:01:20 +0100
From: Xaver Hugl <xaver.hugl@...il.com>
To: Shengyu Qu <wiagn233@...look.com>
Cc: 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
Subject: Re: [PATCH 00/11] Plane Color Pipeline support for MediaTek

Am Mo., 29. Dez. 2025 um 19:53 Uhr schrieb Shengyu Qu <wiagn233@...look.com>:
> > The curves supported by Gamma are:
> > * scRGB
> > * BT.709
> > * BT.2020
> > * HLG
> >
> > 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.
scRGB is a different specification from sRGB and has only piece-wise
and linear, not power 2.2. I seems unlikely that there's really a
problem here.

- Xaver