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

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Message-Id: <DFICN8TKUFBH.1V8WHTIQ5BE2J@cknow-tech.com>
Date: Wed, 07 Jan 2026 13:18:00 +0100
From: "Diederik de Haas" <diederik@...ow-tech.com>
To: "Cristian Ciocaltea" <cristian.ciocaltea@...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>, "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,

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>

Cheers,
  Diederik

> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
> Changes in v3:
> - Added new patches:
>   * uapi: Provide DIV_ROUND_CLOSEST()
>   * drm/vkms: Support setting custom background color
> - Improved DRM_ARGB64_{PREP|GET}*() helpers by using a conversion ratio
>   for better color approximation when dealing with less than 16 bits of
>   precision
> - Mentioned the IGT test in the cover letter while documenting the
>   validation results; also dropped references to the now useless
>   modetest wrapper script and its generated report
> - Rebased series onto latest drm-misc-next
> - Link to v2: https://lore.kernel.org/r/20251013-rk3588-bgcolor-v2-0-25cc3810ba8c@collabora.com
>
> Changes in v2:
> - Improved uAPI consistency and readability by introducing
>   DRM_ARGB64_PREP*() and DRM_ARGB64_GET*() helper macros
> - Updated several code comment sections
> - Referenced the counterpart Weston support in the cover letter
> - Rebased series onto v6.18-rc1
> - Link to v1: https://lore.kernel.org/r/20250902-rk3588-bgcolor-v1-0-fd97df91d89f@collabora.com
>
> ---
> Cristian Ciocaltea (4):
>       uapi: Provide DIV_ROUND_CLOSEST()
>       drm: Add CRTC background color property
>       drm/vkms: Support setting custom background color
>       drm/rockchip: vop2: Support setting custom background color
>
>  drivers/gpu/drm/drm_atomic_state_helper.c    |  1 +
>  drivers/gpu/drm/drm_atomic_uapi.c            |  4 ++
>  drivers/gpu/drm/drm_blend.c                  | 39 ++++++++++++++--
>  drivers/gpu/drm/drm_mode_config.c            |  6 +++
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 13 +++++-
>  drivers/gpu/drm/rockchip/rockchip_drm_vop2.h |  4 ++
>  drivers/gpu/drm/vkms/vkms_composer.c         | 10 ++++-
>  drivers/gpu/drm/vkms/vkms_crtc.c             |  3 ++
>  include/drm/drm_blend.h                      |  4 +-
>  include/drm/drm_crtc.h                       | 12 +++++
>  include/drm/drm_mode_config.h                |  5 +++
>  include/linux/math.h                         | 18 +-------
>  include/uapi/drm/drm_mode.h                  | 67 ++++++++++++++++++++++++++++
>  include/uapi/linux/const.h                   | 17 +++++++
>  14 files changed, 178 insertions(+), 25 deletions(-)
> ---
> base-commit: 92c49b3f4df8f9acfa95551ef38fc00c675319fd
> change-id: 20250829-rk3588-bgcolor-c1a7b9a507bc