A logo or a colour given on the kernel command line was asked for this
very boot: a bootloader that picks the product variant from an EEPROM
and passes it along, a developer, or a production line that turns the
screen red when a test fails. The device tree, the BGRT and the kernel's
defaults describe what the board or the build normally wants. Let the
command line win, as console= wins over stdout-path.

Each parameter wins for what it says, and only when it is given, so
none has a default of its own:

- drm_client_lib.splash_bmp names a BMP to load as firmware, preferred
  over the device tree and the BGRT. Without it the order is unchanged:
  device tree, BGRT, then "drm_splash.bmp" loaded as firmware. An empty
  value counts as not given. A file that is named but missing gives no
  image rather than falling back, since it is what was asked for.

- drm_client_lib.splash_bmp=none asks for no image at all: only the
  background is drawn, whatever the other sources have.

- drm_client_lib.splash_pos=X,Y, splash_offset=DX,DY and
  splash_rotation=0|90|180|270 place and turn the image with the same
  meaning as the device tree properties, whatever the image's source.
  A BMP loaded as firmware has no other way to be placed or turned, and
  for the others they let a placement be tried without rebuilding a
  device tree. Positions take both values or are ignored with a
  warning. When they place a BGRT image, it is placed in screen pixels
  like any other, and neither the table offsets nor the efifb sanity
  check apply.

- drm_client_lib.splash_color sets the background whatever the image.
  Without it the colour comes from the source that supplied the image,
  a device tree node's "background-color", and otherwise from
  CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR. A device tree colour is not
  used around an image named on the command line: it belongs to another
  image.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Màxim Pedraza Padilla <[email protected]>
---
 drivers/gpu/drm/clients/Kconfig      |  20 ++--
 drivers/gpu/drm/clients/drm_splash.c | 171 +++++++++++++++++++++------
 2 files changed, 142 insertions(+), 49 deletions(-)

diff --git a/drivers/gpu/drm/clients/Kconfig b/drivers/gpu/drm/clients/Kconfig
index f471019bab87..2a374bea370b 100644
--- a/drivers/gpu/drm/clients/Kconfig
+++ b/drivers/gpu/drm/clients/Kconfig
@@ -105,11 +105,9 @@ config DRM_CLIENT_SPLASH_BACKGROUND_COLOR
        help
          The default splash background color, in RGB888 format.
 
-         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.
+         The drm_client_lib.splash_color kernel command line parameter, when
+         given, is used whatever the image. Otherwise a device tree image can
+         carry its own color, and this one is used for everything else.
 
 config DRM_CLIENT_SPLASH_SRC_DT
        bool "Device tree as splash source"
@@ -123,8 +121,9 @@ config DRM_CLIENT_SPLASH_SRC_DT
          show a different logo on each board or product, chosen by the
          device tree it boots with.
 
-         When present, the device tree image is preferred over the other
-         sources.
+         When present, the device tree image is preferred over the BGRT and
+         over the default BMP loaded as firmware. A BMP named on the kernel
+         command line is preferred over it.
 
 config DRM_CLIENT_SPLASH_SRC_BGRT
        bool "EFI BGRT as splash source"
@@ -150,9 +149,10 @@ config DRM_CLIENT_SPLASH_SRC_BMP
 
          The image will be loaded using the firmware loading facility the
          kernel provides; it shall use 24 bits per pixel and shall not be
-         compressed. The name of the file can be set through the
-         drm_client_lib.splash_bmp command line parameter, with the default
-         being 'drm_splash.bmp'.
+         compressed. A file named through the drm_client_lib.splash_bmp
+         command line parameter is preferred over any other image source;
+         otherwise 'drm_splash.bmp' is used when neither the device tree nor
+         the BGRT provides an image.
 
 config DRM_CLIENT_SPLASH_BMP_SUPPORT
        bool
diff --git a/drivers/gpu/drm/clients/drm_splash.c 
b/drivers/gpu/drm/clients/drm_splash.c
index 34f3c3910be1..8d056edfee56 100644
--- a/drivers/gpu/drm/clients/drm_splash.c
+++ b/drivers/gpu/drm/clients/drm_splash.c
@@ -40,18 +40,90 @@
  * a static image.
  */
 
-static unsigned int splash_color = CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR;
-module_param(splash_color, uint, 0400);
+/*
+ * What is given on the command line wins over the device tree and the
+ * firmware tables, and each parameter only for what it says. Neither has a
+ * value of its own until it is given: -1 and NULL mean "not given".
+ */
+static int splash_color = -1;
+module_param(splash_color, int, 0400);
 MODULE_PARM_DESC(splash_color,
-                "Background color (RGB888) around the BMP loaded as firmware, 
or of the whole screen with no image");
+                "Background color as 0xRRGGBB, preferred over any other");
+
+static int splash_pos[2];
+static unsigned int splash_pos_n;
+module_param_array(splash_pos, int, &splash_pos_n, 0400);
+MODULE_PARM_DESC(splash_pos,
+                "Image position as X,Y in screen pixels, -1 centres that 
axis");
+
+static int splash_offset[2];
+static unsigned int splash_offset_n;
+module_param_array(splash_offset, int, &splash_offset_n, 0400);
+MODULE_PARM_DESC(splash_offset,
+                "Displacement as DX,DY in screen pixels, added after placing");
+
+static int splash_rotation = -1;
+module_param(splash_rotation, int, 0400);
+MODULE_PARM_DESC(splash_rotation,
+                "Image rotation in degrees counter clockwise: 0, 90, 180 or 
270");
 
 #if IS_ENABLED(CONFIG_DRM_CLIENT_SPLASH_SRC_BMP)
 #define DEFAULT_SPLASH_BMP "drm_splash.bmp"
-static char *splash_bmp = DEFAULT_SPLASH_BMP;
+static char *splash_bmp;
 module_param(splash_bmp, charp, 0400);
-MODULE_PARM_DESC(splash_bmp, "Name of splash image (default: \"" 
DEFAULT_SPLASH_BMP "\")");
+MODULE_PARM_DESC(splash_bmp,
+                "BMP to load as firmware, preferred over any other image");
+
+/* Given on the command line, and not empty */
+static bool drm_splash_bmp_given(void)
+{
+       return splash_bmp && *splash_bmp;
+}
+
+/* "none" asks for no image at all, whatever the other sources have */
+static bool drm_splash_bmp_none(void)
+{
+       return drm_splash_bmp_given() && !strcmp(splash_bmp, "none");
+}
+
+static const char *drm_splash_bmp_name(void)
+{
+       return drm_splash_bmp_given() ? splash_bmp : DEFAULT_SPLASH_BMP;
+}
+#else
+static inline bool drm_splash_bmp_given(void)
+{
+       return false;
+}
+
+static inline bool drm_splash_bmp_none(void)
+{
+       return false;
+}
 #endif // CONFIG_DRM_CLIENT_SPLASH_SRC_BMP
 
+/* Degrees counter clockwise, as for panels, and as DRM counts them */
+static bool drm_splash_rotation_from_degrees(u32 degrees,
+                                            unsigned int *rotation)
+{
+       switch (degrees) {
+       case 0:
+               *rotation = DRM_MODE_ROTATE_0;
+               return true;
+       case 90:
+               *rotation = DRM_MODE_ROTATE_90;
+               return true;
+       case 180:
+               *rotation = DRM_MODE_ROTATE_180;
+               return true;
+       case 270:
+               *rotation = DRM_MODE_ROTATE_270;
+               return true;
+       }
+
+       return false;
+}
+
 #define BMP_FILE_MAGIC_ID 0x4d42
 
 /* BMP header structures copied from drivers/video/fbdev/efifb.c */
@@ -132,6 +204,8 @@ struct drm_splash {
        s32 off_x, off_y;
        /* One of DRM_MODE_ROTATE_*: turns the image, not the screen */
        unsigned int rotation;
+       /* Placed from the command line, in screen pixels, whatever the source 
*/
+       bool place_cmdline;
        /* RGB888, from the same place as the image */
        u32 bg_color;
 };
@@ -210,10 +284,11 @@ static int drm_splash_fw_request_bmp(struct drm_splash 
*splash)
 {
        struct drm_client_dev *client = &splash->client;
 
-       drm_info(client->dev, "splash: request %s as firmware", splash_bmp);
+       drm_info(client->dev, "splash: request %s as firmware",
+                drm_splash_bmp_name());
 
        return request_firmware_nowait(THIS_MODULE, FW_ACTION_UEVENT,
-                                      splash_bmp, client->dev->dev, GFP_KERNEL,
+                                      drm_splash_bmp_name(), client->dev->dev, 
GFP_KERNEL,
                                       splash, drm_splash_fw_callback);
 }
 #else
@@ -272,11 +347,9 @@ static void drm_splash_dt_props(struct drm_splash *splash,
 {
        u32 val[2];
 
-       /* The colour travels with the image, or it is the kernel's default */
+       /* The colour travels with the image */
        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];
@@ -288,27 +361,10 @@ static void drm_splash_dt_props(struct drm_splash *splash,
                splash->off_y = (s32)val[1];
        }
 
-       /* Degrees counter clockwise, as for panels, and as DRM counts them */
-       if (!of_property_read_u32(np, "rotation", &val[0])) {
-               switch (val[0]) {
-               case 0:
-                       splash->rotation = DRM_MODE_ROTATE_0;
-                       break;
-               case 90:
-                       splash->rotation = DRM_MODE_ROTATE_90;
-                       break;
-               case 180:
-                       splash->rotation = DRM_MODE_ROTATE_180;
-                       break;
-               case 270:
-                       splash->rotation = DRM_MODE_ROTATE_270;
-                       break;
-               default:
-                       drm_warn(splash->client.dev,
-                                "splash: %pOF: unsupported rotation %u",
-                                np, val[0]);
-               }
-       }
+       if (!of_property_read_u32(np, "rotation", &val[0]) &&
+           !drm_splash_rotation_from_degrees(val[0], &splash->rotation))
+               drm_warn(splash->client.dev,
+                        "splash: %pOF: unsupported rotation %u", np, val[0]);
 }
 
 static int drm_splash_dt_load(struct drm_splash *splash, const u8 **data,
@@ -733,7 +789,7 @@ static int drm_splash_bmp_to_scanout(struct drm_splash 
*splash,
                return -EINVAL;
        }
 
-       if (splash->src == DRM_SPLASH_SRC_BGRT) {
+       if (splash->src == DRM_SPLASH_SRC_BGRT && !splash->place_cmdline) {
                /*
                 * The BGRT offsets place the upright image on the upright
                 * screen, which for a panel mounted turned is not the frame
@@ -858,10 +914,53 @@ static int drm_splash_image_load(struct drm_splash 
*splash, const u8 **img_data,
  * is whatever the firmware shows, and the BMP loaded as firmware is the
  * fallback. With none of them, only the background colour is drawn.
  */
+/*
+ * What the command line gives wins whatever the image and its source, each
+ * parameter for what it says. Positions come in pairs: half of one is
+ * ignored rather than guessed.
+ */
+static void drm_splash_cmdline_overrides(struct drm_splash *splash)
+{
+       struct drm_device *dev = splash->client.dev;
+
+       if (splash_color >= 0)
+               splash->bg_color = splash_color & 0xffffff;
+
+       if (splash_pos_n == 2) {
+               splash->pos_x = splash_pos[0];
+               splash->pos_y = splash_pos[1];
+               splash->place_cmdline = true;
+       } else if (splash_pos_n) {
+               drm_warn(dev, "splash: splash_pos needs X,Y, ignored");
+       }
+
+       if (splash_offset_n == 2) {
+               splash->off_x = splash_offset[0];
+               splash->off_y = splash_offset[1];
+               splash->place_cmdline = true;
+       } else if (splash_offset_n) {
+               drm_warn(dev, "splash: splash_offset needs DX,DY, ignored");
+       }
+
+       if (splash_rotation >= 0 &&
+           !drm_splash_rotation_from_degrees(splash_rotation, 
&splash->rotation))
+               drm_warn(dev, "splash: unsupported splash_rotation %d, ignored",
+                        splash_rotation);
+}
+
 static enum drm_splash_source drm_splash_pick_source(struct drm_splash *splash)
 {
        struct device_node *np;
 
+       /* Unless the source says otherwise, the kernel's default colour */
+       splash->bg_color = CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR;
+
+       /* A BMP named on the command line was asked for this very boot */
+       if (drm_splash_bmp_none())
+               return DRM_SPLASH_SRC_NONE;
+       if (drm_splash_bmp_given())
+               return DRM_SPLASH_SRC_BMP;
+
        np = drm_splash_dt_node(splash);
        if (np) {
                drm_splash_dt_props(splash, np);
@@ -869,18 +968,11 @@ static enum drm_splash_source 
drm_splash_pick_source(struct drm_splash *splash)
                return DRM_SPLASH_SRC_DT;
        }
 
-       /* 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;
                splash->rotation = drm_splash_bgrt_rotation();
                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;
 
@@ -1181,6 +1273,7 @@ static int drm_splash_client_hotplug(struct 
drm_client_dev *client)
        splash->thread = thread;
 
        splash->src = drm_splash_pick_source(splash);
+       drm_splash_cmdline_overrides(splash);
 
        /* The BMP loaded as firmware is the only source that arrives later */
        if (splash->src == DRM_SPLASH_SRC_BMP) {
-- 
2.39.5

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