[PATCH RFC v4 08/13] drm/client: splash: place the device tree image where it asks

[Màxim Pedraza Padilla]

A logo supplied by the device tree describes a particular product, and
where it lands on the panel matters: some panels only show part of the
mode, so the middle of the mode is not the middle of what the user
sees.

Read the optional "logo-position" and "logo-offset" properties of the
node. The position is the top left corner, with -1 on an axis meaning
centre on that axis, and the offset is added afterwards, which is the
only way to say "below the centre" when the device tree does not know
the image size, as with an image in a reserved region.

Both come straight from the device tree, so the sum is done in 64 bits
and clamped, and a silly pair of values lands the image against an
edge rather than off the screen: the blitters do not clip. Every other
source keeps being centred, except the BGRT, which keeps its own
offsets.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Màxim Pedraza Padilla <maximpedraza@xxxxxxxxx>
---
 drivers/gpu/drm/clients/drm_splash.c | 73 ++++++++++++++++++++++++----
 1 file changed, 63 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/clients/drm_splash.c b/drivers/gpu/drm/clients/drm_splash.c
index 444f612c48ac..349f68d392e5 100644
--- a/drivers/gpu/drm/clients/drm_splash.c
+++ b/drivers/gpu/drm/clients/drm_splash.c
@@ -120,6 +120,14 @@ struct drm_splash {
 	void *map_data;
 
 	enum drm_splash_source src;
+
+	/*
+	 * Where the image goes, in screen pixels: a coordinate of -1 centres
+	 * it on that axis, and the offset is added afterwards. Only the device
+	 * tree asks for anything but the centre.
+	 */
+	s32 pos_x, pos_y;
+	s32 off_x, off_y;
 };
 
 static struct drm_splash *client_to_drm_splash(struct drm_client_dev *client)
@@ -252,13 +260,21 @@ static struct device_node *drm_splash_dt_node(struct drm_splash *splash)
 	return NULL;
 }
 
-static bool drm_splash_dt_available(struct drm_splash *splash)
+/* The optional placement properties of the node, read once */
+static void drm_splash_dt_placement(struct drm_splash *splash,
+				    struct device_node *np)
 {
-	struct device_node *np = drm_splash_dt_node(splash);
+	u32 val[2];
 
-	of_node_put(np);
+	if (!of_property_read_u32_array(np, "logo-position", val, 2)) {
+		splash->pos_x = (s32)val[0];
+		splash->pos_y = (s32)val[1];
+	}
 
-	return np;
+	if (!of_property_read_u32_array(np, "logo-offset", val, 2)) {
+		splash->off_x = (s32)val[0];
+		splash->off_y = (s32)val[1];
+	}
 }
 
 static int drm_splash_dt_load(struct drm_splash *splash, const u8 **data,
@@ -311,9 +327,14 @@ static int drm_splash_dt_load(struct drm_splash *splash, const u8 **data,
 	return ret;
 }
 #else
-static inline bool drm_splash_dt_available(struct drm_splash *splash)
+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)
 {
-	return false;
 }
 
 static inline int drm_splash_dt_load(struct drm_splash *splash,
@@ -459,6 +480,26 @@ static int drm_splash_fill_solid_color(struct drm_client_buffer *buffer,
 }
 
 #if IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_BMP_SUPPORT)
+/*
+ * Place the image along one axis of the screen. @pos is the coordinate asked
+ * for, or -1 to centre on that axis, and @off is added afterwards. Both may
+ * come from the device tree, so the sum is done wide enough not to wrap, and
+ * the result keeps the whole image on the screen: the blitters do not clip.
+ */
+static unsigned int drm_splash_place_axis(s32 pos, s32 off, unsigned int span,
+					  unsigned int size)
+{
+	s64 last = (s64)span - size;
+	s64 coord;
+
+	if (last <= 0)
+		return 0;
+
+	coord = pos == -1 ? last / 2 : pos;
+
+	return clamp_t(s64, coord + off, 0, last);
+}
+
 static void drm_splash_blit_pix16(struct iosys_map *map, unsigned int dpitch,
 				  unsigned int x_pad, unsigned int y_pad,
 				  const u8 *sbuf8, unsigned int spitch,
@@ -657,9 +698,10 @@ static int drm_splash_bmp_to_scanout(struct drm_splash *splash,
 		}
 #endif
 	} else {
-		/* Center X and Y */
-		x_pad = (scanout->width - bmp_width) / 2;
-		y_pad = (scanout->height - bmp_height) / 2;
+		x_pad = drm_splash_place_axis(splash->pos_x, splash->off_x,
+					      scanout->width, bmp_width);
+		y_pad = drm_splash_place_axis(splash->pos_y, splash->off_y,
+					      scanout->height, bmp_height);
 	}
 
 	image_data = data + bitmap_offset;
@@ -742,8 +784,15 @@ static int drm_splash_image_load(struct drm_splash *splash, const u8 **img_data,
  */
 static enum drm_splash_source drm_splash_pick_source(struct drm_splash *splash)
 {
-	if (drm_splash_dt_available(splash))
+	struct device_node *np;
+
+	np = drm_splash_dt_node(splash);
+	if (np) {
+		drm_splash_dt_placement(splash, np);
+		of_node_put(np);
 		return DRM_SPLASH_SRC_DT;
+	}
+
 	if (drm_splash_bgrt_available(splash))
 		return DRM_SPLASH_SRC_BGRT;
 	if (IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_SRC_BMP))
@@ -1141,6 +1190,10 @@ void drm_splash_register(struct drm_device *dev,
 	spin_lock_init(&splash->fw_lock);
 	init_completion(&splash->fw_done);
 
+	/* Centred unless the image source asks otherwise */
+	splash->pos_x = -1;
+	splash->pos_y = -1;
+
 	if (format && format->num_planes == 1)
 		splash->preferred_format = format->format;
 	else
-- 
2.39.5