linux-kernel - Re: [PATCH v7 3/4] drm/vkms: Support setting custom background color

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Message-ID: <e6dd0f45-1d64-48b8-bc76-43cc29fabec2@bootlin.com>
Date: Fri, 6 Feb 2026 15:04:51 +0100
From: Louis Chauvet <louis.chauvet@...tlin.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>,
 Haneen Mohammed <hamohammed.sa@...il.com>,
 Melissa Wen <melissa.srw@...il.com>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.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,
 Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Diederik de Haas <diederik@...ow-tech.com>
Subject: Re: [PATCH v7 3/4] drm/vkms: Support setting custom background color



On 2/4/26 21:02, Cristian Ciocaltea wrote:
> Make use of the BACKGROUND_COLOR CRTC property when filling the
> background during blending.  It already defaults to solid black.
> 
> Since the internal representation of the pixel color in VKMS relies on
> 16 bits of precision, use the newly introduced DRM_ARGB64_GET{R|G|B}()
> helpers to access the individual components of the background color
> property, which is compliant with DRM_FORMAT_ARGB16161616.
> 
> It's worth noting the alpha component is ignored, hence non-opaque
> background colors are not supported.
> 
> Reviewed-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

Reviewed-by: Louis Chauvet <louis.chauvet@...tlin.com>

> Tested-by: Diederik de Haas <diederik@...ow-tech.com>
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>   drivers/gpu/drm/vkms/vkms_composer.c | 10 ++++++++--
>   drivers/gpu/drm/vkms/vkms_crtc.c     |  3 +++
>   2 files changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
> index cd85de4ffd03..83d217085ad0 100644
> --- a/drivers/gpu/drm/vkms/vkms_composer.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -475,8 +475,14 @@ static void blend(struct vkms_writeback_job *wb,
>   {
>   	struct vkms_plane_state **plane = crtc_state->active_planes;
>   	u32 n_active_planes = crtc_state->num_active_planes;
> -
> -	const struct pixel_argb_u16 background_color = { .a = 0xffff };
> +	u64 bgcolor = crtc_state->base.background_color;
> +
> +	const struct pixel_argb_u16 background_color = {
> +		.a = 0xffff,
> +		.r = DRM_ARGB64_GETR(bgcolor),
> +		.g = DRM_ARGB64_GETG(bgcolor),
> +		.b = DRM_ARGB64_GETB(bgcolor),
> +	};
>   
>   	int crtc_y_limit = crtc_state->base.mode.vdisplay;
>   	int crtc_x_limit = crtc_state->base.mode.hdisplay;
> diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> index 9a7db1d51022..2514c367f710 100644
> --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> @@ -4,6 +4,7 @@
>   
>   #include <drm/drm_atomic.h>
>   #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_blend.h>
>   #include <drm/drm_managed.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_probe_helper.h>
> @@ -228,6 +229,8 @@ struct vkms_output *vkms_crtc_init(struct drm_device *dev, struct drm_plane *pri
>   
>   	drm_crtc_enable_color_mgmt(crtc, 0, false, VKMS_LUT_SIZE);
>   
> +	drm_crtc_attach_background_color_property(crtc);
> +
>   	spin_lock_init(&vkms_out->lock);
>   	spin_lock_init(&vkms_out->composer_lock);
>   
>