linux-kernel - Re: [PATCH v3 0/4] Introduce BACKGROUND

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Message-ID: <0cce5e09-1947-46b4-8ffc-1aa880accc9a@collabora.com>
Date: Wed, 7 Jan 2026 19:54:56 +0200
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Diederik de Haas <diederik@...ow-tech.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>,
 Sandy Huang <hjc@...k-chips.com>, Heiko Stübner
 <heiko@...ech.de>, Andy Yan <andy.yan@...k-chips.com>,
 Louis Chauvet <louis.chauvet@...tlin.com>,
 Haneen Mohammed <hamohammed.sa@...il.com>,
 Melissa Wen <melissa.srw@...il.com>
Cc: Robert Mader <robert.mader@...labora.com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 Matt Roper <matthew.d.roper@...el.com>
Subject: Re: [PATCH v3 0/4] Introduce BACKGROUND_COLOR DRM CRTC property

Hi Diederik,

On 1/7/26 2:18 PM, Diederik de Haas wrote:
> Hi,
> 
> On Tue Nov 18, 2025 at 12:51 AM CET, Cristian Ciocaltea wrote:
>> Some display controllers can be hardware-configured to present non-black
>> colors for pixels which are not covered by any plane (or are exposed
>> through transparent regions of higher planes).
>> ...
>> The subsequent patches add background color support to VKMS and the VOP2
>> display controller used in the RK3568, RK3576, and RK3588 Rockchip SoC
>> families.
> 
> Cristian provided a helper script which would show a test pattern and
> then iterate through setting Red, Green, Blue background color and then
> set it back to the original value.
> 
> I first tested this on a Rock 5B (RK3588).
> Without this patch set, the background color was Black with every
> iteration. But with this patch set, I did see a Red, Green and Blue
> background color, after which it was set back to Black.
> 
> diederik@...k5b:~$ grep -E "^Changing prop|^Read BACKGROUND_COLOR" bgcol-test-bash-user.log
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff000000000000
> Changing prop value to: 0xffff00000000ffff
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff00000000ffff
> Changing prop value to 0xffffffff00000000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffffffff00000000
> Changing prop value to 0xffff0000ffff0000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff0000ffff0000
> Changing prop value to 0xffff00000000ffff
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff00000000ffff
> Changing prop value to: 0xffff000000000000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff000000000000
> 
> I then did the same test on a Quartz64-B (RK3566) and that too showed a
> Red, Green and Blue background color and then was set back to Black.
> 
> diederik@...rtz64b:~$ grep -E "^Changing prop|^Read BACKGROUND_COLOR" bgcol-test-bash-user-q64b.log
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff000000000000
> Changing prop value to: 0xffff00000000ffff
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff00000000ffff
> Changing prop value to 0xffffffff00000000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffffffff00000000
> Changing prop value to 0xffff0000ffff0000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff0000ffff0000
> Changing prop value to 0xffff00000000ffff
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff00000000ffff
> Changing prop value to: 0xffff000000000000
> Read BACKGROUND_COLOR prop (ARGB64): 0xffff000000000000
> 
> So this patch set does what it is supposed to do, so feel free to add:
> 
> Tested-by: Diederik de Haas <diederik@...ow-tech.com>

Thanks for taking the time to test this!

Please note there's a newer revision of the series:

https://lore.kernel.org/all/20251219-rk3588-bgcolor-v4-0-2ff1127ea757@collabora.com/

Regards,
Cristian