linux-kernel - Re: [PATCH v3 20/33] drm/vkms: Introduce config for plane zpos property

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Message-Id: <DF5P2XO5NLXX.YYEZNVLERBLU@bootlin.com>
Date: Tue, 23 Dec 2025 16:18:04 +0100
From: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
To: "Louis Chauvet" <louis.chauvet@...tlin.com>, "Haneen Mohammed"
 <hamohammed.sa@...il.com>, "Simona Vetter" <simona@...ll.ch>, "Melissa Wen"
 <melissa.srw@...il.com>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "David Airlie"
 <airlied@...il.com>, <jose.exposito89@...il.com>, "Jonathan Corbet"
 <corbet@....net>
Cc: <victoria@...tem76.com>, <sebastian.wick@...hat.com>,
 <thomas.petazzoni@...tlin.com>, <dri-devel@...ts.freedesktop.org>,
 <linux-kernel@...r.kernel.org>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v3 20/33] drm/vkms: Introduce config for plane zpos
 property

On Mon Dec 22, 2025 at 11:11 AM CET, Louis Chauvet wrote:
> VKMS can render plane in any order. Introduce the appropriate
> configuration.
>
> Signed-off-by: Louis Chauvet <louis.chauvet@...tlin.com>

> @@ -253,6 +256,33 @@ bool vkms_config_valid_plane_color_range(const struct vkms_config *config,
>  }
>  EXPORT_SYMBOL_IF_KUNIT(vkms_config_valid_plane_color_range);
>
> +VISIBLE_IF_KUNIT
> +bool vkms_config_valid_plane_zpos(const struct vkms_config *config,
> +				  const struct vkms_config_plane *plane_cfg)
> +{
> +	struct drm_device *dev = config->dev ? &config->dev->drm : NULL;
> +
> +	if (!vkms_config_plane_get_zpos_enabled(plane_cfg) ||
> +	    !vkms_config_plane_get_zpos_mutable(plane_cfg))
> +		return true;
> +
> +	if (vkms_config_plane_get_zpos_initial(plane_cfg) >
> +	    vkms_config_plane_get_zpos_max(plane_cfg)) {
> +		drm_info(dev, "Configured initial zpos value bigger than zpos max\n");
> +		return false;
> +	}
> +
> +	if (vkms_config_plane_get_zpos_max(plane_cfg) <
> +	    vkms_config_plane_get_zpos_min(plane_cfg) ||
> +	    vkms_config_plane_get_zpos_initial(plane_cfg) <
> +	    vkms_config_plane_get_zpos_min(plane_cfg)) {
> +		drm_info(dev, "Configured zpos value outside (zpos min; zpos max)\n");
> +		return false;
> +	}

Weird grouping. It should rather be:

 if (max < min) {...}

 if (initial > max || initial < min) {...}

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com