[PATCH RFC v4 10/13] drm/client: splash: take the background colour from the image source

[Màxim Pedraza Padilla]

A logo designed for a light background looks wrong framed in black, and
products that share a board support package differ in their colours as
much as in their logos. The background colour belongs with the image,
so take it from the same place:

- a device tree image uses the optional "background-color" of its node;
- the BGRT carries no colour, and firmware splashes sit on black, so it
  uses the kernel's default;
- the BMP loaded as firmware is named on the command line, and so is its
  colour, through drm_client_lib.splash_color, which also covers the
  screen when there is no image at all.

CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR remains the default wherever
the source says nothing. The command line no longer overrides a device
tree image: a bootloader that wants another colour for a given boot,
say to flag a failed test on a production line, changes the node.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Màxim Pedraza Padilla <maximpedraza@xxxxxxxxx>
---
 drivers/gpu/drm/clients/Kconfig      |  7 ++++--
 drivers/gpu/drm/clients/drm_splash.c | 36 +++++++++++++++++++++-------
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/clients/Kconfig b/drivers/gpu/drm/clients/Kconfig
index aef3781cc110..f471019bab87 100644
--- a/drivers/gpu/drm/clients/Kconfig
+++ b/drivers/gpu/drm/clients/Kconfig
@@ -105,8 +105,11 @@ config DRM_CLIENT_SPLASH_BACKGROUND_COLOR
 	help
 	  The default splash background color, in RGB888 format.
 
-	  The color can be overridden through the drm_client_lib.splash_color
-	  kernel command line parameter.
+	  The background color comes from the same place as the image. A
+	  device tree image can carry its own, and the drm_client_lib.splash_color
+	  kernel command line parameter sets it for a BMP loaded as firmware,
+	  or for the whole screen when there is no image. This color is used
+	  otherwise, and always with the BGRT image, which carries none.
 
 config DRM_CLIENT_SPLASH_SRC_DT
 	bool "Device tree as splash source"
diff --git a/drivers/gpu/drm/clients/drm_splash.c b/drivers/gpu/drm/clients/drm_splash.c
index 924bc0032d1d..30ba6573424e 100644
--- a/drivers/gpu/drm/clients/drm_splash.c
+++ b/drivers/gpu/drm/clients/drm_splash.c
@@ -42,7 +42,8 @@
 
 static unsigned int splash_color = CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR;
 module_param(splash_color, uint, 0400);
-MODULE_PARM_DESC(splash_color, "Splash background color (RGB888)");
+MODULE_PARM_DESC(splash_color,
+		 "Background color (RGB888) around the BMP loaded as firmware, or of the whole screen with no image");
 
 #if IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_SRC_BMP)
 #define DEFAULT_SPLASH_BMP "drm_splash.bmp"
@@ -131,6 +132,8 @@ struct drm_splash {
 	s32 off_x, off_y;
 	/* One of DRM_MODE_ROTATE_*: turns the image, not the screen */
 	unsigned int rotation;
+	/* RGB888, from the same place as the image */
+	u32 bg_color;
 };
 
 static struct drm_splash *client_to_drm_splash(struct drm_client_dev *client)
@@ -263,12 +266,18 @@ static struct device_node *drm_splash_dt_node(struct drm_splash *splash)
 	return NULL;
 }
 
-/* The optional placement properties of the node, read once */
-static void drm_splash_dt_placement(struct drm_splash *splash,
-				    struct device_node *np)
+/* The optional properties of the node, read once */
+static void drm_splash_dt_props(struct drm_splash *splash,
+				struct device_node *np)
 {
 	u32 val[2];
 
+	/* The colour travels with the image, or it is the kernel's default */
+	if (!of_property_read_u32(np, "background-color", &val[0]))
+		splash->bg_color = val[0] & 0xffffff;
+	else
+		splash->bg_color = CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR;
+
 	if (!of_property_read_u32_array(np, "logo-position", val, 2)) {
 		splash->pos_x = (s32)val[0];
 		splash->pos_y = (s32)val[1];
@@ -357,8 +366,8 @@ static inline struct device_node *drm_splash_dt_node(struct drm_splash *splash)
 	return NULL;
 }
 
-static inline void drm_splash_dt_placement(struct drm_splash *splash,
-					   struct device_node *np)
+static inline void drm_splash_dt_props(struct drm_splash *splash,
+				       struct device_node *np)
 {
 }
 
@@ -801,13 +810,22 @@ static enum drm_splash_source drm_splash_pick_source(struct drm_splash *splash)
 
 	np = drm_splash_dt_node(splash);
 	if (np) {
-		drm_splash_dt_placement(splash, np);
+		drm_splash_dt_props(splash, np);
 		of_node_put(np);
 		return DRM_SPLASH_SRC_DT;
 	}
 
-	if (drm_splash_bgrt_available(splash))
+	/* The BGRT carries no colour: firmware splashes sit on black */
+	if (drm_splash_bgrt_available(splash)) {
+		splash->bg_color = CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR;
 		return DRM_SPLASH_SRC_BGRT;
+	}
+
+	/*
+	 * The BMP loaded as firmware is named on the command line, and so is
+	 * its colour, which also covers the screen when there is no image.
+	 */
+	splash->bg_color = splash_color & 0xffffff;
 	if (IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_SRC_BMP))
 		return DRM_SPLASH_SRC_BMP;
 
@@ -865,7 +883,7 @@ static int drm_splash_render_thread(void *data)
 
 			if (!scanout->bg_drawn) {
 				drm_dbg(client->dev, "draw background for scanout %d", i);
-				u32 color = drm_draw_color_from_xrgb8888(splash_color,
+				u32 color = drm_draw_color_from_xrgb8888(splash->bg_color,
 									 scanout->format);
 				drm_splash_fill_solid_color(scanout->buffer, color);
 				scanout->bg_drawn = true;
-- 
2.39.5