[PATCH RFC 0/3] Add splash DRM client

[PATCH RFC 0/3] Add splash DRM client

[Francesco Valla]

Hello,

this patchset adds a new DRM client offering splash functionalities,
able to draw to screen:

  - a colored background;
  - a single-line text message, which can be set through sysfs or
    directly from the kernel command line;
  - a very simple progress bar, which can be driven through sysfs;
  - a static image (optional).

Once compiled inside the kernel, the client can be enabled through the
command line specifying the drm_client_lib.active=splash parameter.

== Motivation ==

The motivation behind this work is to offer to embedded system
developers a new path for a simple activation of the display(s)
connected to their system, with the following usecases:

  - bootsplash - possibly displaying even before init;
  - early activation of the display pipeline, in particular whenever one
    component of the pipeline (e.g.: a panel) takes a non-negligible
    time to initialize;
  - recovery systems, where the splash client can offer a simple feedback
    for unattended recovery tasks;
  - update systems, where the splash client can offer a simple feedback
    for unattended update tasks.

While the first seems the most obvious one, it was the second that acted
as the driver, as in the past I had to implement a ugly workaround using
a systemd generator to kickstart the initialization of a display and
shave ~400ms of boot time.

The last 2 usecase, instead, are the reason I dropped the "boot" part
from bootsplash.

== Implementation details ==

The design is quite simple, with a kernel thread doing the heavylifting
for the rendering part and some locking to protect interactions with it.

The splash image is loaded using the firmware framework, with the client
expecting to find a binary dump having the right dimensions (width and
height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
modeset, the client will for example search for a firmware named:

   drm_splash_1920x1080_RG24.raw

If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
mechanism is used to let userspace load the appropriate image.

== Testing ==

Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
display connected to a Beagleplay and on a ILI9341 SPI display connected
to a i.MX93 FRDM board. All these platforms revealed different
weaknesses that were hopefully removed.

== Open points / issues ==

The reason for this being an RFC is that there are several open points:

  - Support for tiled connectors should be there, but has not been
    tested. Any idea on how to test it?
  - I'm not entirely convinced that using the firmware framework to load
    the images is the right path. The idea behind it was to re-use the
    compressed firmware support, but then I discovered it is not there
    for built-in firmware.
  - Again on the firmware loading: CONFIG_LOADPIN would interfere with
    sysfs loading.
  - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
    leading me to think it is de-facto deprecated. And still, uevents
    for firmware loading seem frowned upon these days... 
  - Generating binary dumps for... basically any format is not so
    straightforward. I crafted a Python tool with AI help which seems
    to work quite well, but I honestly did not yet understood which is
    the policy for AI-generated code inside the kernel, so it is not
    included in this patch set. All client code is genuine, though.

== Additional notes ==

A bootsplash client was one of the TODOs for the DRM subsystem, so patch
3 removes the relative section from the list.

Curious to hear your thoughts. Thank you in advance!

Best regards,
Francesco

Signed-off-by: Francesco Valla <francesco@valla.it>
---
Francesco Valla (3):
      drm: client: add splash client
      MAINTAINERS: add entry for DRM splash client
      drm: docs: remove bootsplash from TODO

 Documentation/gpu/todo.rst                    |  17 -
 MAINTAINERS                                   |   7 +
 drivers/gpu/drm/clients/Kconfig               |  46 +-
 drivers/gpu/drm/clients/Makefile              |   1 +
 drivers/gpu/drm/clients/drm_client_internal.h |   9 +
 drivers/gpu/drm/clients/drm_client_setup.c    |   8 +
 drivers/gpu/drm/clients/drm_splash.c          | 761 ++++++++++++++++++++++++++
 7 files changed, 831 insertions(+), 18 deletions(-)
---
base-commit: 4bb1f7e19c4a1d6eeb52b80acff5ac63edd1b91d
change-id: 20251026-drm_client_splash-e10d7d663e7f

Best regards,
-- 
Francesco Valla <francesco@valla.it>

[PATCH RFC 1/3] drm: client: add splash client

[Francesco Valla]

Add a DRM client that draws a simple splash, with possibility to show:

  - a colored background
  - a text message
  - a progress bar
  - (optionally) a static splash image

The client is not meant to replace a full-featured bootsplash, but
rather to remove some complexity (and hopefully boot time) on small
embedded platforms or on systems with a limited scope (e.g: recovery
or manufacturing images).

The text message and the progress bar can be set through sysfs
properties; a default value for the former can also be set from the
kernel command line using the drm_client_lib.message="<...>" parameter.

If enabled, the splash image is loaded as firmware for each DRM device.
The splash client expects this image to be a binary dump of the graphic
buffer to be shown on the screen connected to the modeset, with the
same dimensions (width and height) and color format.

Just like the existing DRM clients, the splash can be enable from the
kernel command line using drm_client_lib.active=splash.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 drivers/gpu/drm/clients/Kconfig               |  46 +-
 drivers/gpu/drm/clients/Makefile              |   1 +
 drivers/gpu/drm/clients/drm_client_internal.h |   9 +
 drivers/gpu/drm/clients/drm_client_setup.c    |   8 +
 drivers/gpu/drm/clients/drm_splash.c          | 761 ++++++++++++++++++++++++++
 5 files changed, 824 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/clients/Kconfig b/drivers/gpu/drm/clients/Kconfig
index 6096c623d9d5b1a3d4a40d986c45aad2f8277767..0b23756f2453c9b815d9f242987d5f386b7a894f 100644
--- a/drivers/gpu/drm/clients/Kconfig
+++ b/drivers/gpu/drm/clients/Kconfig
@@ -12,6 +12,7 @@ config DRM_CLIENT_LIB
 config DRM_CLIENT_SELECTION
 	tristate
 	depends on DRM
+	select DRM_CLIENT_LIB if DRM_CLIENT_SPLASH
 	select DRM_CLIENT_LIB if DRM_CLIENT_LOG
 	select DRM_CLIENT_LIB if DRM_FBDEV_EMULATION
 	help
@@ -85,10 +86,46 @@ config DRM_CLIENT_LOG
 	  If you only need logs, but no terminal, or if you prefer userspace
 	  terminal, say "Y".
 
+config DRM_CLIENT_SPLASH
+	bool "Display graphical splash"
+	depends on DRM_CLIENT_SELECTION
+	select DRM_CLIENT
+	select DRM_CLIENT_SETUP
+	select DRM_DRAW
+	select FONT_SUPPORT
+	help
+	  This enables a splash drm client, able to display a colored background,
+	  a progress bar, some text and (optionally, if DRM_CLIENT_SPLASH_LOAD_AS_FW
+	  is set) a graphical image until the userspace is ready to take over.
+
+	  Message and progress can be set through sysfs; an initial message can also
+	  be set by using the kernel command line 'drm_client_lib.message=' option.
+
+config DRM_CLIENT_SPLASH_FOREGROUND_COLOR
+	hex "Splash foreground color, in RGB"
+	depends on DRM_CLIENT_SPLASH
+	default 0xffffff
+
+config DRM_CLIENT_SPLASH_BACKGROUND_COLOR
+	hex "Splash background color, in RGB"
+	depends on DRM_CLIENT_SPLASH
+	default 0x000000
+
+config DRM_CLIENT_SPLASH_LOAD_AS_FW
+	bool "Load splash image as firmware"
+	depends on DRM_CLIENT_SPLASH
+	select FW_LOADER
+	help
+	  Load image to be used as splash using the firmware loading facility the
+	  kernel provides.
+
+	  Even when this option is set, the image loading can be avoided by using
+	  the kernel command line 'drm_client_lib.skip_image=true' option.
+
 choice
 	prompt "Default DRM Client"
 	depends on DRM_CLIENT_SELECTION
-	depends on DRM_FBDEV_EMULATION || DRM_CLIENT_LOG
+	depends on DRM_FBDEV_EMULATION || DRM_CLIENT_LOG || DRM_CLIENT_SPLASH
 	default DRM_CLIENT_DEFAULT_FBDEV
 	help
 	  Selects the default drm client.
@@ -111,6 +148,12 @@ config DRM_CLIENT_DEFAULT_LOG
 	  screen, but doesn't implement a full terminal. For that you will need
 	  a userspace terminal using drm/kms.
 
+config DRM_CLIENT_DEFAULT_SPLASH
+	bool "splash"
+	depends on DRM_CLIENT_SPLASH
+	help
+	  Use splash as default drm client.
+
 endchoice
 
 config DRM_CLIENT_DEFAULT
@@ -118,6 +161,7 @@ config DRM_CLIENT_DEFAULT
        depends on DRM_CLIENT
        default "fbdev" if DRM_CLIENT_DEFAULT_FBDEV
        default "log" if DRM_CLIENT_DEFAULT_LOG
+       default "splash" if DRM_CLIENT_DEFAULT_SPLASH
        default ""
 
 endmenu
diff --git a/drivers/gpu/drm/clients/Makefile b/drivers/gpu/drm/clients/Makefile
index c16addbc327f09572aa3142cbf0d1d13f172a9e9..3df02d10cd18a47d7e8d7cee70163b0ef0129b51 100644
--- a/drivers/gpu/drm/clients/Makefile
+++ b/drivers/gpu/drm/clients/Makefile
@@ -5,4 +5,5 @@ subdir-ccflags-y += -I$(src)/..
 drm_client_lib-y := drm_client_setup.o
 drm_client_lib-$(CONFIG_DRM_CLIENT_LOG) += drm_log.o
 drm_client_lib-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fbdev_client.o
+drm_client_lib-$(CONFIG_DRM_CLIENT_SPLASH) += drm_splash.o
 obj-$(CONFIG_DRM_CLIENT_LIB) += drm_client_lib.o
diff --git a/drivers/gpu/drm/clients/drm_client_internal.h b/drivers/gpu/drm/clients/drm_client_internal.h
index 6dc078bf6503b902cbb3267b64ea42d9f1c23375..48ee0c1c2529882b2bf5dc786788390823e25cd6 100644
--- a/drivers/gpu/drm/clients/drm_client_internal.h
+++ b/drivers/gpu/drm/clients/drm_client_internal.h
@@ -22,4 +22,13 @@ void drm_log_register(struct drm_device *dev);
 static inline void drm_log_register(struct drm_device *dev) {}
 #endif
 
+#ifdef CONFIG_DRM_CLIENT_SPLASH
+void drm_splash_register(struct drm_device *dev,
+			 const struct drm_format_info *format);
+#else
+static inline void drm_splash_register(struct drm_device *dev,
+				       const struct drm_format_info *format)
+{}
+#endif
+
 #endif
diff --git a/drivers/gpu/drm/clients/drm_client_setup.c b/drivers/gpu/drm/clients/drm_client_setup.c
index 72480db1f00d0b9fcd1fe5aa72a3a31a074393b2..023a142319227c5f7ba887dcd55af4b04942f9ce 100644
--- a/drivers/gpu/drm/clients/drm_client_setup.c
+++ b/drivers/gpu/drm/clients/drm_client_setup.c
@@ -56,6 +56,14 @@ void drm_client_setup(struct drm_device *dev, const struct drm_format_info *form
 		return;
 	}
 #endif
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH
+	if (!strcmp(drm_client_default, "splash")) {
+		drm_splash_register(dev, format);
+		return;
+	}
+#endif
+
 	if (strcmp(drm_client_default, ""))
 		drm_warn(dev, "Unknown DRM client %s\n", drm_client_default);
 }
diff --git a/drivers/gpu/drm/clients/drm_splash.c b/drivers/gpu/drm/clients/drm_splash.c
new file mode 100644
index 0000000000000000000000000000000000000000..308924e917e32d1e6d7686bf6f9b3a3ff2bafe68
--- /dev/null
+++ b/drivers/gpu/drm/clients/drm_splash.c
@@ -0,0 +1,761 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/*
+ * Copyright (c) 2025 Francesco Valla <francesco@valla.it>
+ *
+ */
+
+#include <linux/atomic.h>
+#include <linux/device.h>
+#include <linux/firmware.h>
+#include <linux/font.h>
+#include <linux/init.h>
+#include <linux/iosys-map.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include <drm/drm_client.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_framebuffer.h>
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+
+#include "drm_client_internal.h"
+#include "drm_draw_internal.h"
+#include "drm_internal.h"
+
+// TODO: determine proper size for max message length
+#define DRM_SPLASH_MAX_MSG_LEN 128
+
+static char *message;
+module_param(message, charp, 0400);
+MODULE_PARM_DESC(message, "Initial message, up to " __stringify(DRM_SPLASH_MAX_MSG_LEN) " chars");
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+static bool skip_image;
+module_param(skip_image, bool, 0400);
+MODULE_PARM_DESC(skip_image, "Do not try to load splash image (default: false)");
+#endif
+
+/**
+ * DOC: overview
+ *
+ * This is a simple graphic bootsplash.
+ * Images to be shown are loaded as firmware.
+ */
+
+struct drm_splash_scanout {
+	int id;
+	u32 format;
+	unsigned int width;
+	unsigned int height;
+	struct drm_client_buffer *buffer;
+
+	struct mutex lock;
+	const struct font_desc *font;
+	bool bg_drawn;
+	bool message_drawn;
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+	const struct firmware *fw;
+#endif
+};
+
+struct drm_splash {
+	struct drm_client_dev client;
+	u32 preferred_format;
+	struct device dev;
+
+	struct mutex lock;
+	struct task_struct *thread;
+	atomic_t pending;
+	bool initialized;
+
+	char message[DRM_SPLASH_MAX_MSG_LEN];
+	u8 progress;
+
+	u32 n_scanout;
+	struct drm_splash_scanout *scanout;
+};
+
+static struct drm_splash *client_to_drm_splash(struct drm_client_dev *client)
+{
+	return container_of_const(client, struct drm_splash, client);
+}
+
+static struct drm_splash_scanout *
+get_scanout_from_tile_group(struct drm_splash *splash, int id)
+{
+	int j;
+
+	for (j = 0; j < splash->n_scanout; j++)
+		if (splash->scanout[j].id == id)
+			return &splash->scanout[j];
+
+	return NULL;
+}
+
+static u32 drm_splash_find_usable_format(struct drm_plane *plane,
+					 u32 preferred_format)
+{
+	int i;
+
+	/* If preferred format is not set, use RGB888 (which offers full colors
+	 * with minimal occupation).
+	 */
+	if (preferred_format == 0)
+		preferred_format = DRM_FORMAT_RGB888;
+
+	/* Check if the preferred format can be used */
+	for (i = 0; i < plane->format_count; i++)
+		if (plane->format_types[i] == preferred_format)
+			return preferred_format;
+
+	/* Otherwise, find the first format that can be converted from XRGB8888 */
+	for (i = 0; i < plane->format_count; i++)
+		if (drm_draw_color_from_xrgb8888(0xffffffff, plane->format_types[i]) != 0)
+			return plane->format_types[i];
+
+	return DRM_FORMAT_INVALID;
+}
+
+static void drm_splash_blit(struct iosys_map *dst, unsigned int dst_pitch,
+			    const u8 *src, unsigned int src_pitch,
+			    u32 height, u32 width, u32 px_width, u32 color)
+{
+	switch (px_width) {
+	case 2:
+		drm_draw_blit16(dst, dst_pitch, src, src_pitch, height, width, 1, color);
+		break;
+	case 3:
+		drm_draw_blit24(dst, dst_pitch, src, src_pitch, height, width, 1, color);
+		break;
+	case 4:
+		drm_draw_blit32(dst, dst_pitch, src, src_pitch, height, width, 1, color);
+		break;
+	default:
+		WARN_ONCE(1, "Can't blit with pixel width %d\n", px_width);
+	}
+}
+
+static void drm_splash_fill(struct iosys_map *map, unsigned int dst_pitch,
+			    unsigned int height, unsigned int width,
+			    u32 px_width, u32 color)
+{
+	switch (px_width) {
+	case 2:
+		drm_draw_fill16(map, dst_pitch, height, width, color);
+		break;
+	case 3:
+		drm_draw_fill24(map, dst_pitch, height, width, color);
+		break;
+	case 4:
+		drm_draw_fill32(map, dst_pitch, height, width, color);
+		break;
+	default:
+		WARN_ONCE(1, "Can't fill with pixel width %d\n", px_width);
+	}
+}
+
+static int drm_splash_fill_solid_color(struct drm_client_buffer *buffer, u32 color)
+{
+	struct drm_client_dev *client = buffer->client;
+	struct drm_framebuffer *fb = buffer->fb;
+	struct drm_rect r = DRM_RECT_INIT(0, 0, fb->width, fb->height);
+	u32 px_width = fb->format->cpp[0];
+	struct iosys_map map;
+	int ret;
+
+	ret = drm_client_buffer_vmap_local(buffer, &map);
+	if (ret) {
+		drm_err(client->dev, "splash: cannot vmap buffer: %d", ret);
+		return ret;
+	}
+
+	drm_splash_fill(&map, fb->pitches[0], drm_rect_height(&r),
+			drm_rect_width(&r), px_width, color);
+
+	drm_client_buffer_vunmap_local(buffer);
+
+	return drm_client_framebuffer_flush(buffer, &r);
+}
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+static int drm_splash_fill_from_data(struct drm_client_buffer *buffer,
+				     const u8 *data, size_t data_len)
+{
+	struct drm_client_dev *client = buffer->client;
+	struct drm_framebuffer *fb = buffer->fb;
+	struct drm_rect r = DRM_RECT_INIT(0, 0, fb->width, fb->height);
+	struct iosys_map map;
+	size_t buffer_size;
+	int ret;
+
+	buffer_size = fb->width * fb->height * fb->format->cpp[0];
+	if (data_len != buffer_size) {
+		drm_err(client->dev,
+			"splash: data size mismatch (expected %zu, got %zu)",
+			data_len, buffer_size);
+		return -ENODATA;
+	}
+
+	ret = drm_client_buffer_vmap_local(buffer, &map);
+	if (ret) {
+		drm_err(client->dev, "splash: cannot vmap buffer: %d", ret);
+		return ret;
+	}
+
+	iosys_map_memcpy_to(&map, 0, data, data_len);
+
+	drm_client_buffer_vunmap_local(buffer);
+
+	return drm_client_framebuffer_flush(buffer, &r);
+}
+#endif
+
+static int drm_splash_draw_bar_message(struct drm_splash_scanout *scanout,
+				       const char *msg,
+				       unsigned int progress,
+				       u32 bg_color,
+				       u32 fg_color)
+{
+	struct drm_framebuffer *fb = scanout->buffer->fb;
+	const struct font_desc *font = scanout->font;
+	size_t font_pitch = DIV_ROUND_UP(font->width, 8);
+	u32 px_width = fb->format->cpp[0];
+	unsigned int y_padding = 2;
+	struct drm_rect r = DRM_RECT_INIT(0, fb->height * 3 / 4 - y_padding,
+					  fb->width, font->height + y_padding);
+	unsigned int fill_width = drm_rect_width(&r) * progress / 100;
+	struct iosys_map map;
+	const u8 *src;
+	size_t i, len;
+
+	/* Clamp len if required */
+	len = min(strlen(msg), drm_rect_width(&r) / font->width);
+
+	if (drm_client_buffer_vmap_local(scanout->buffer, &map))
+		return -1;
+
+	/* Draw progress bar */
+	iosys_map_incr(&map, r.y1 * fb->pitches[0]);
+	drm_splash_fill(&map, fb->pitches[0], drm_rect_height(&r),
+			drm_rect_width(&r), px_width, bg_color);
+	drm_splash_fill(&map, fb->pitches[0], drm_rect_height(&r),
+			fill_width, px_width, fg_color);
+
+	/* Center the message horizontally */
+	iosys_map_incr(&map, y_padding * fb->pitches[0]);
+	iosys_map_incr(&map, (drm_rect_width(&r) - (font->width * len)) * px_width / 2);
+
+	/* Write message */
+	for (i = 0; i < len; i++) {
+		unsigned int ch_x;
+
+		src = drm_draw_get_char_bitmap(font, msg[i], font_pitch);
+
+		/* Use background color over fill bar, foreground otherwise */
+		ch_x = (drm_rect_width(&r) - font->width * len) / 2 + i * font->width;
+		drm_splash_blit(&map, fb->pitches[0], src, font_pitch,
+				font->height, font->width, px_width,
+				(fill_width > ch_x) ? bg_color : fg_color);
+		iosys_map_incr(&map, font->width * px_width);
+	}
+
+	drm_client_buffer_vunmap_local(scanout->buffer);
+	drm_client_framebuffer_flush(scanout->buffer, &r);
+
+	return 0;
+}
+
+static int drm_splash_draw_scanout(struct drm_splash_scanout *scanout,
+				   const char *msg, unsigned int progress)
+{
+	u32 bg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_CLIENT_SPLASH_BACKGROUND_COLOR,
+						    scanout->format);
+	u32 fg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_CLIENT_SPLASH_FOREGROUND_COLOR,
+						    scanout->format);
+	int ret = -ENOENT;
+
+	if (!scanout->buffer)
+		return -ENODEV;
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+	if (!skip_image) {
+		const struct firmware *fw = NULL;
+
+		scoped_guard(mutex, &scanout->lock) {
+			fw = scanout->fw;
+			scanout->fw = NULL;
+		}
+
+		if (fw) {
+			ret = drm_splash_fill_from_data(scanout->buffer,
+							fw->data, fw->size);
+			release_firmware(fw);
+
+			if (ret == 0)
+				scanout->bg_drawn = true;
+		}
+	}
+#endif
+
+	/* If no firmware has been used to fill the screen (either by choice of
+	 * because it's unavailable) fill the screen with the background color.
+	 *
+	 */
+	if (!scanout->bg_drawn) {
+		drm_splash_fill_solid_color(scanout->buffer, bg_color);
+		scanout->bg_drawn = true;
+	}
+
+	/* If message is empty and no previous message was shown, there is
+	 * nothing to do
+	 */
+	if (scanout->message_drawn || strlen(msg) != 0 || progress != 0) {
+		ret = drm_splash_draw_bar_message(scanout, msg, progress,
+						  bg_color, fg_color);
+		if (ret)
+			return ret;
+
+		scanout->message_drawn = true;
+	}
+
+	return 0;
+}
+
+static int drm_splash_render_thread(void *data)
+{
+	struct drm_splash *splash = data;
+	struct drm_client_dev *client = &splash->client;
+	char buf[sizeof(splash->message)];
+	unsigned int progress;
+
+	while (!kthread_should_stop()) {
+		unsigned int draw_count = 0;
+		int j, ret;
+
+		/* Copy message and progress to be drawn, to avoid locking for
+		 * too much time and/or showing different contents on different
+		 * screens.
+		 */
+		scoped_guard(mutex, &splash->lock) {
+			strscpy(buf, splash->message);
+			progress = splash->progress;
+		}
+
+		for (j = 0; j < splash->n_scanout; j++) {
+			ret = drm_splash_draw_scanout(&splash->scanout[j], buf,
+						      progress);
+			if (ret) {
+				drm_err(client->dev,
+					"splash: failed to fill scanout %d: %d",
+					j, ret);
+				continue;
+			}
+
+			draw_count++;
+		}
+
+		if (draw_count > 0) {
+			ret = drm_client_modeset_commit(client);
+			/* If commit returns EBUSY, another master showed up.
+			 * This means that the splash is no more required.
+			 */
+			if (ret == -EBUSY) {
+				drm_info(client->dev,
+					"splash: not master anymore, exiting");
+				break;
+			}
+		}
+
+		/* If no changes arrived in the mean time, wait to be awaken by
+		 * a sysfs write, a firmware callback or a stop command.
+		 */
+		if (atomic_xchg(&splash->pending, 0) == 0)
+			set_current_state(TASK_UNINTERRUPTIBLE);
+
+		schedule();
+	}
+
+	return 0;
+}
+
+static inline void drm_splash_wake_render_thread(struct drm_splash *splash)
+{
+	atomic_set(&splash->pending, 1);
+	wake_up_process(splash->thread);
+}
+
+static int drm_splash_init_client(struct drm_splash *splash)
+{
+	struct drm_client_dev *client = &splash->client;
+	struct drm_mode_set *modeset;
+	unsigned int modeset_mask = 0;
+	unsigned int fb_count = 0;
+	int j;
+
+	if (drm_client_modeset_probe(client, 0, 0))
+		return -1;
+
+	j = 0;
+	drm_client_for_each_modeset(modeset, client) {
+		struct drm_splash_scanout *tmp;
+		struct drm_splash_scanout *scanout;
+		u32 format;
+		int id = -1;
+
+		/* Skip modesets without a mode */
+		if (!modeset->mode)
+			continue;
+
+		if (modeset->connectors[0]->has_tile) {
+			struct drm_splash_scanout *tiled;
+			int new_id = modeset->connectors[0]->tile_group->id;
+
+			/* Tiled modesets contribute to a single framebuffer,
+			 * check if this tiled group has already been seen.
+			 */
+			tiled = get_scanout_from_tile_group(splash, new_id);
+			if (tiled != NULL) {
+				if (!modeset->x)
+					tiled->width += modeset->mode->vdisplay;
+				if (!modeset->y)
+					tiled->height += modeset->mode->hdisplay;
+				modeset->fb = tiled->buffer->fb;
+				continue;
+			}
+
+			/* New tile group, save its ID for later */
+			id = new_id;
+		}
+
+		format = drm_splash_find_usable_format(modeset->crtc->primary,
+						       splash->preferred_format);
+		if (format == DRM_FORMAT_INVALID) {
+			drm_warn(client->dev,
+				 "splash: can't find a usable format for modeset");
+			continue;
+		}
+
+		tmp = krealloc(splash->scanout,
+			       (splash->n_scanout + 1) * sizeof(*splash->scanout),
+			       GFP_KERNEL);
+		if (!tmp) {
+			drm_warn(client->dev,
+				 "splash: can't reallocate the scanout array");
+			break;
+		}
+
+		splash->scanout = tmp;
+		scanout = &splash->scanout[splash->n_scanout];
+		splash->n_scanout++;
+
+		memset(scanout, 0, sizeof(*scanout));
+		scanout->id = id;
+		scanout->format = format;
+		scanout->width = modeset->mode->hdisplay;
+		scanout->height = modeset->mode->vdisplay;
+		mutex_init(&scanout->lock);
+
+		modeset_mask |= BIT(j);
+		j++;
+	}
+
+	/* Now that all sensible modesets have been collected, allocate buffers */
+	j = 0;
+	drm_client_for_each_modeset(modeset, client) {
+		struct drm_splash_scanout *scanout;
+
+		if (!(modeset_mask & BIT(j)))
+			continue;
+
+		scanout = &splash->scanout[j];
+		j++;
+
+		scanout->buffer = drm_client_framebuffer_create(client,
+								scanout->width,
+								scanout->height,
+								scanout->format);
+		if (IS_ERR(scanout->buffer)) {
+			drm_warn(client->dev,
+				 "splash: can't create framebuffer %d %d %p4cc",
+				 scanout->width, scanout->height, &scanout->format);
+			continue;
+		}
+
+		drm_info(client->dev, "splash: created framebuffer %d %d %p4cc",
+			 scanout->width, scanout->height, &scanout->format);
+
+		scanout->font = get_default_font(scanout->width, scanout->height,
+						 NULL, NULL);
+		if (!scanout->font) {
+			drm_warn(client->dev,
+				 "splash: failed to get default font");
+		}
+
+		modeset->fb = scanout->buffer->fb;
+		fb_count++;
+	}
+
+	return (fb_count == 0) ? -ENODEV : 0;
+}
+
+static void drm_splash_free_scanout(struct drm_client_dev *client)
+{
+	struct drm_splash *splash = client_to_drm_splash(client);
+	int i;
+
+	if (splash->n_scanout) {
+		for (i = 0; i < splash->n_scanout; i++) {
+			drm_client_framebuffer_delete(splash->scanout[i].buffer);
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+			if (splash->scanout[i].fw)
+				release_firmware(splash->scanout[i].fw);
+#endif
+			mutex_destroy(&splash->scanout[i].lock);
+		}
+		splash->n_scanout = 0;
+		kfree(splash->scanout);
+		splash->scanout = NULL;
+	}
+}
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+static void drm_splash_fw_callback(const struct firmware *fw, void *context)
+{
+	struct drm_splash_scanout *scanout = context;
+	struct drm_client_dev *client = scanout->buffer->client;
+	struct drm_splash *splash = client_to_drm_splash(client);
+
+	if (!fw || !fw->data) {
+		drm_err(client->dev, "splash: no firmware");
+		return;
+	}
+
+	/* Assign new firmware to the scanout */
+	scoped_guard(mutex, &scanout->lock) {
+		if (scanout->fw)
+			release_firmware(scanout->fw);
+		scanout->fw = fw;
+	}
+
+	/* Wake the render thread */
+	drm_dbg(client->dev, "splash: firmware loaded, wake up drawing thread");
+	drm_splash_wake_render_thread(splash);
+}
+
+static int drm_splash_kick_fw_load(struct drm_splash *splash,
+				   struct task_struct *thread)
+{
+	struct drm_client_dev *client = &splash->client;
+	int j;
+
+	for (j = 0; j < splash->n_scanout; j++) {
+		struct drm_splash_scanout *scanout = &splash->scanout[j];
+		char *fw_name = kasprintf(GFP_KERNEL,
+					  "drm_splash_%ux%u_%.4s.raw",
+					  scanout->width, scanout->height,
+					  (const char *)&scanout->format);
+		if (!fw_name)
+			return -ENOMEM;
+
+		drm_dbg(client->dev, "splash: request firmware %s", fw_name);
+		request_firmware_nowait(THIS_MODULE, FW_ACTION_NOUEVENT, fw_name,
+					&splash->dev, GFP_KERNEL,
+					scanout, drm_splash_fw_callback);
+		kfree(fw_name);
+	}
+
+	return 0;
+}
+#endif /* CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW */
+
+static int drm_splash_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_splash *splash = client_to_drm_splash(client);
+	int ret;
+
+	guard(mutex)(&splash->lock);
+
+	/* The modesets that get a splash are defined at first hotplug event */
+	if (splash->initialized)
+		return 0;
+
+	ret = drm_splash_init_client(splash);
+	if (ret == -ENODEV) {
+		drm_info(client->dev, "splash: no modeset found");
+		return 0;
+	} else if (ret) {
+		drm_err(client->dev,
+			"splash: failed to init client: %d", ret);
+		return ret;
+	}
+
+	/* Create the render thread, waken later */
+	splash->thread = kthread_create(drm_splash_render_thread,
+					splash, "drm_splash_%s",
+					client->dev->unique);
+	if (IS_ERR(splash->thread)) {
+		ret = PTR_ERR(splash->thread);
+		drm_err(client->dev, "splash: failed to create render thread: %d", ret);
+		drm_splash_free_scanout(client);
+		return ret;
+	}
+
+#ifdef CONFIG_DRM_CLIENT_SPLASH_LOAD_AS_FW
+	if (!skip_image) {
+		ret = drm_splash_kick_fw_load(splash, splash->thread);
+		if (ret) {
+			drm_err(client->dev, "splash: failed to kick fw load: %d", ret);
+			kthread_stop(splash->thread);
+			drm_splash_free_scanout(client);
+			return ret;
+		}
+	}
+#endif
+
+	/* Wake the render thread to show initial contents */
+	drm_splash_wake_render_thread(splash);
+
+	splash->initialized = true;
+
+	return 0;
+}
+
+static void drm_splash_client_unregister(struct drm_client_dev *client)
+{
+	struct drm_splash *splash = client_to_drm_splash(client);
+	struct drm_device *dev = client->dev;
+
+	kthread_stop(splash->thread);
+	device_del(&splash->dev);
+	drm_splash_free_scanout(client);
+	drm_client_release(client);
+	put_device(&splash->dev);
+	kfree(splash);
+	drm_dbg(dev, "Unregistered with drm splash");
+}
+
+static const struct drm_client_funcs drm_splash_client_funcs = {
+	.owner		= THIS_MODULE,
+	.hotplug	= drm_splash_client_hotplug,
+	.unregister	= drm_splash_client_unregister,
+};
+
+static ssize_t progress_store(struct device *device,
+			      struct device_attribute *attr,
+			      const char *buf,
+			      size_t count)
+{
+	struct drm_splash *splash = dev_get_drvdata(device);
+	u8 progress;
+	int ret;
+
+	ret = kstrtou8(buf, 0, &progress);
+	if (ret)
+		return ret;
+
+	if (ret > 100)
+		return -ERANGE;
+
+	scoped_guard(mutex, &splash->lock)
+		splash->progress = progress;
+
+	drm_splash_wake_render_thread(splash);
+
+	return count;
+}
+DEVICE_ATTR_WO(progress);
+
+static ssize_t message_store(struct device *device,
+			     struct device_attribute *attr,
+			     const char *buf,
+			     size_t count)
+{
+	struct drm_splash *splash = dev_get_drvdata(device);
+	size_t len = min(count, sizeof(splash->message));
+
+	scoped_guard(mutex, &splash->lock)
+		strscpy(splash->message, buf, len);
+
+	drm_splash_wake_render_thread(splash);
+
+	return count;
+}
+DEVICE_ATTR_WO(message);
+
+static ssize_t stop_store(struct device *device,
+			  struct device_attribute *attr,
+			  const char *buf,
+			  size_t count)
+{
+	struct drm_splash *splash = dev_get_drvdata(device);
+	unsigned long val;
+	int ret;
+
+	ret = kstrtoul(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (val != 0)
+		kthread_stop(splash->thread);
+
+	return count;
+}
+DEVICE_ATTR_WO(stop);
+
+static struct attribute *drm_splash_attrs[] = {
+	&dev_attr_message.attr,
+	&dev_attr_progress.attr,
+	&dev_attr_stop.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(drm_splash);
+
+/**
+ * drm_splash_register() - Register a drm device to drm_splash
+ * @dev: the drm device to register.
+ * @format: drm device preferred format.
+ */
+void drm_splash_register(struct drm_device *dev,
+			 const struct drm_format_info *format)
+{
+	struct drm_splash *splash;
+	int ret;
+
+	splash = kzalloc(sizeof(*splash), GFP_KERNEL);
+	if (!splash)
+		goto err_warn;
+
+	mutex_init(&splash->lock);
+	if (format && format->num_planes == 1)
+		splash->preferred_format = format->format;
+
+	if (message)
+		strscpy(splash->message, message);
+
+	if (drm_client_init(dev, &splash->client, "drm_splash",
+			    &drm_splash_client_funcs))
+		goto err_free;
+
+	device_initialize(&splash->dev);
+	splash->dev.parent = dev->dev;
+	splash->dev.groups = drm_splash_groups;
+	dev_set_name(&splash->dev, "drm_splash");
+	dev_set_drvdata(&splash->dev, splash);
+	ret = device_add(&splash->dev);
+	if (ret)
+		goto err_free;
+
+	drm_client_register(&splash->client);
+	drm_dbg(dev, "Registered with drm splash");
+
+	return;
+
+err_free:
+	kfree(splash);
+err_warn:
+	drm_warn(dev, "Failed to register with drm splash");
+}

-- 
2.51.0

[PATCH RFC 2/3] MAINTAINERS: add entry for DRM splash client

[Francesco Valla]

Add myself as maintainer for the DRM splash client.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 MAINTAINERS | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 3da2c26a796b82b9de4143c1591a9b1d44d42194..b365a6199dd427b0c66452cbc419d1fc0618c502 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8643,6 +8643,13 @@ T:	git https://gitlab.freedesktop.org/drm/misc/kernel.git
 F:	drivers/gpu/drm/drm_privacy_screen*
 F:	include/drm/drm_privacy_screen*
 
+DRM SPLASH
+M:	Francesco Valla <francesco@valla.it>
+L:	dri-devel@lists.freedesktop.org
+S:	Maintained
+T:	git https://gitlab.freedesktop.org/drm/misc/kernel.git
+F:	drivers/gpu/drm/clients/drm_splash.c
+
 DRM TTM SUBSYSTEM
 M:	Christian Koenig <christian.koenig@amd.com>
 M:	Huang Rui <ray.huang@amd.com>

-- 
2.51.0

[PATCH RFC 3/3] drm: docs: remove bootsplash from TODO

[Francesco Valla]

Now that a splash client exists, remove the bootsplash task from the
TODO list for the DRM subsystem.

Signed-off-by: Francesco Valla <francesco@valla.it>
---
 Documentation/gpu/todo.rst | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
index b5f58b4274b1d38e26b229b88a8b4f4ba3433179..b1a6d587c286f060d549a12cf8e771f753b712bc 100644
--- a/Documentation/gpu/todo.rst
+++ b/Documentation/gpu/todo.rst
@@ -717,23 +717,6 @@ See drivers/gpu/drm/amd/display/TODO for tasks.
 
 Contact: Harry Wentland, Alex Deucher
 
-Bootsplash
-==========
-
-There is support in place now for writing internal DRM clients making it
-possible to pick up the bootsplash work that was rejected because it was written
-for fbdev.
-
-- [v6,8/8] drm/client: Hack: Add bootsplash example
-  https://patchwork.freedesktop.org/patch/306579/
-
-- [RFC PATCH v2 00/13] Kernel based bootsplash
-  https://lore.kernel.org/r/20171213194755.3409-1-mstaudt@suse.de
-
-Contact: Sam Ravnborg
-
-Level: Advanced
-
 Brightness handling on devices with multiple internal panels
 ============================================================
 

-- 
2.51.0

Re: [PATCH RFC 0/3] Add splash DRM client

[Maxime Ripard]

[-- Attachment #1: Type: text/plain, Size: 4423 bytes --]

Hi,

On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
> this patchset adds a new DRM client offering splash functionalities,
> able to draw to screen:
> 
>   - a colored background;

So, I like that part, and we were recently discussing about this.

>   - a single-line text message, which can be set through sysfs or
>     directly from the kernel command line;
>   - a very simple progress bar, which can be driven through sysfs;
>   - a static image (optional).

But there's no reason to have all that in the kernel, and we already
have userspace components to do so (plymouth being the main "mainstream"
one).

> Once compiled inside the kernel, the client can be enabled through the
> command line specifying the drm_client_lib.active=splash parameter.
> 
> == Motivation ==
> 
> The motivation behind this work is to offer to embedded system
> developers a new path for a simple activation of the display(s)
> connected to their system, with the following usecases:
> 
>   - bootsplash - possibly displaying even before init;
>   - early activation of the display pipeline, in particular whenever one
>     component of the pipeline (e.g.: a panel) takes a non-negligible
>     time to initialize;
>   - recovery systems, where the splash client can offer a simple feedback
>     for unattended recovery tasks;
>   - update systems, where the splash client can offer a simple feedback
>     for unattended update tasks.

If plymouth cannot be used by embedded systems for some reason, then you
should work on a plymouth alternative.

> While the first seems the most obvious one, it was the second that acted
> as the driver, as in the past I had to implement a ugly workaround using
> a systemd generator to kickstart the initialization of a display and
> shave ~400ms of boot time.
> 
> The last 2 usecase, instead, are the reason I dropped the "boot" part
> from bootsplash.
> 
> == Implementation details ==
> 
> The design is quite simple, with a kernel thread doing the heavylifting
> for the rendering part and some locking to protect interactions with it.
> 
> The splash image is loaded using the firmware framework, with the client
> expecting to find a binary dump having the right dimensions (width and
> height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
> modeset, the client will for example search for a firmware named:
> 
>    drm_splash_1920x1080_RG24.raw
> 
> If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
> mechanism is used to let userspace load the appropriate image.
> 
> == Testing ==
> 
> Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
> display connected to a Beagleplay and on a ILI9341 SPI display connected
> to a i.MX93 FRDM board. All these platforms revealed different
> weaknesses that were hopefully removed.
> 
> == Open points / issues ==
> 
> The reason for this being an RFC is that there are several open points:
> 
>   - Support for tiled connectors should be there, but has not been
>     tested. Any idea on how to test it?

Did you mean tiled formats?

>   - I'm not entirely convinced that using the firmware framework to load
>     the images is the right path. The idea behind it was to re-use the
>     compressed firmware support, but then I discovered it is not there
>     for built-in firmware.

Yeah, firmware loading for this has a few issues (being tedious to setup
for when built-in being one). I think just going the fbdev penguin road
is a better choice: you provide the path, and it's embedded in the
kernel directly.

>   - Again on the firmware loading: CONFIG_LOADPIN would interfere with
>     sysfs loading.
>   - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
>     leading me to think it is de-facto deprecated. And still, uevents
>     for firmware loading seem frowned upon these days... 
>   - Generating binary dumps for... basically any format is not so
>     straightforward. I crafted a Python tool with AI help which seems
>     to work quite well, but I honestly did not yet understood which is
>     the policy for AI-generated code inside the kernel, so it is not
>     included in this patch set. All client code is genuine, though.

BMP is simple enough to support so we should probably use that instead
of a custom format.

Maxime

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 273 bytes --]

Re: [PATCH RFC 0/3] Add splash DRM client

[Thomas Zimmermann]

Hi Francenso, Maxime,

Am 27.10.25 um 11:09 schrieb Maxime Ripard:
> Hi,
>
> On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
>> this patchset adds a new DRM client offering splash functionalities,
>> able to draw to screen:
>>
>>    - a colored background;
> So, I like that part, and we were recently discussing about this.

The panic screen has configurable foreground/background colors. Maybe we 
can harmonize these settings.

>
>>    - a single-line text message, which can be set through sysfs or
>>      directly from the kernel command line;

Put it into the kernel config.

>>    - a very simple progress bar, which can be driven through sysfs;

Once you have options to control these settings from user space, you 
should do it in user space entirely. As Maxime suggested, please improve 
plymouth for anything with animation.

>>    - a static image (optional).

Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This 
is a candidate for display, or the penguin or a custom image. Please 
make it configurable by Kconfig. Again, if you need policy and 
heuristics for deciding what to display, you better do this in user space.

> But there's no reason to have all that in the kernel, and we already
> have userspace components to do so (plymouth being the main "mainstream"
> one).
>
>> Once compiled inside the kernel, the client can be enabled through the
>> command line specifying the drm_client_lib.active=splash parameter.
>>
>> == Motivation ==
>>
>> The motivation behind this work is to offer to embedded system
>> developers a new path for a simple activation of the display(s)
>> connected to their system, with the following usecases:
>>
>>    - bootsplash - possibly displaying even before init;
>>    - early activation of the display pipeline, in particular whenever one
>>      component of the pipeline (e.g.: a panel) takes a non-negligible
>>      time to initialize;
>>    - recovery systems, where the splash client can offer a simple feedback
>>      for unattended recovery tasks;
>>    - update systems, where the splash client can offer a simple feedback
>>      for unattended update tasks.
> If plymouth cannot be used by embedded systems for some reason, then you
> should work on a plymouth alternative.

Agreed. With an updater running in user space, that process should also 
manage the display update. No need for this in the kernel.

>
>> While the first seems the most obvious one, it was the second that acted
>> as the driver, as in the past I had to implement a ugly workaround using
>> a systemd generator to kickstart the initialization of a display and
>> shave ~400ms of boot time.
>>
>> The last 2 usecase, instead, are the reason I dropped the "boot" part
>> from bootsplash.
>>
>> == Implementation details ==
>>
>> The design is quite simple, with a kernel thread doing the heavylifting
>> for the rendering part and some locking to protect interactions with it.
>>
>> The splash image is loaded using the firmware framework, with the client
>> expecting to find a binary dump having the right dimensions (width and
>> height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
>> modeset, the client will for example search for a firmware named:
>>
>>     drm_splash_1920x1080_RG24.raw
>>
>> If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
>> mechanism is used to let userspace load the appropriate image.
>>
>> == Testing ==
>>
>> Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
>> display connected to a Beagleplay and on a ILI9341 SPI display connected
>> to a i.MX93 FRDM board. All these platforms revealed different
>> weaknesses that were hopefully removed.
>>
>> == Open points / issues ==
>>
>> The reason for this being an RFC is that there are several open points:
>>
>>    - Support for tiled connectors should be there, but has not been
>>      tested. Any idea on how to test it?
> Did you mean tiled formats?
>
>>    - I'm not entirely convinced that using the firmware framework to load
>>      the images is the right path. The idea behind it was to re-use the
>>      compressed firmware support, but then I discovered it is not there
>>      for built-in firmware.
> Yeah, firmware loading for this has a few issues (being tedious to setup
> for when built-in being one). I think just going the fbdev penguin road
> is a better choice: you provide the path, and it's embedded in the
> kernel directly.
>
>>    - Again on the firmware loading: CONFIG_LOADPIN would interfere with
>>      sysfs loading.
>>    - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
>>      leading me to think it is de-facto deprecated. And still, uevents
>>      for firmware loading seem frowned upon these days...
>>    - Generating binary dumps for... basically any format is not so
>>      straightforward. I crafted a Python tool with AI help which seems
>>      to work quite well, but I honestly did not yet understood which is
>>      the policy for AI-generated code inside the kernel, so it is not
>>      included in this patch set. All client code is genuine, though.
> BMP is simple enough to support so we should probably use that instead
> of a custom format.

file /sys/firmware/acpi/bgrt/image
/sys/firmware/acpi/bgrt/image: PC bitmap, Windows 3.x format, 768 x 256 
x 24, image size 589824, cbSize 589878, bits offset 54

That should probably be the format for now unless your firmware uses 
something else natively. Code for reading a BMP file can be found in the 
efifb driver. [1]

[1] 
https://elixir.bootlin.com/linux/v6.17.5/source/drivers/video/fbdev/efifb.c#L24

Apart from the criticism for complexity, I do like the idea of having a 
splash screen.

Best regards
Thomas

>
> Maxime

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)

Re: [PATCH RFC 0/3] Add splash DRM client

[Mario Limonciello]

On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
> Hi Francenso, Maxime,
> 
> Am 27.10.25 um 11:09 schrieb Maxime Ripard:
>> Hi,
>>
>> On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
>>> this patchset adds a new DRM client offering splash functionalities,
>>> able to draw to screen:
>>>
>>>    - a colored background;
>> So, I like that part, and we were recently discussing about this.
> 
> The panic screen has configurable foreground/background colors. Maybe we 
> can harmonize these settings.
> 
>>
>>>    - a single-line text message, which can be set through sysfs or
>>>      directly from the kernel command line;
> 
> Put it into the kernel config.
> 
>>>    - a very simple progress bar, which can be driven through sysfs;
> 
> Once you have options to control these settings from user space, you 
> should do it in user space entirely. As Maxime suggested, please improve 
> plymouth for anything with animation.
> 
>>>    - a static image (optional).
> 
> Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This 
> is a candidate for display, or the penguin or a custom image. Please 
> make it configurable by Kconfig. Again, if you need policy and 
> heuristics for deciding what to display, you better do this in user space.

I'd actually argue that the static image from BGRT should be the 
preferred priority.  This can make for a nice hand off to Plymouth.

The (UEFI) BIOS already will show this image as soon as the GOP driver 
is loaded.  Bootloaders like GRUB by default will avoid showing anything 
or will overwrite with the exact same image in the same location.  This 
can let the kernel do the same, and then the moment Plymouth takes over 
it could do the same.
> 
>> But there's no reason to have all that in the kernel, and we already
>> have userspace components to do so (plymouth being the main "mainstream"
>> one).
>>
>>> Once compiled inside the kernel, the client can be enabled through the
>>> command line specifying the drm_client_lib.active=splash parameter.
>>>
>>> == Motivation ==
>>>
>>> The motivation behind this work is to offer to embedded system
>>> developers a new path for a simple activation of the display(s)
>>> connected to their system, with the following usecases:
>>>
>>>    - bootsplash - possibly displaying even before init;
>>>    - early activation of the display pipeline, in particular whenever 
>>> one
>>>      component of the pipeline (e.g.: a panel) takes a non-negligible
>>>      time to initialize;
>>>    - recovery systems, where the splash client can offer a simple 
>>> feedback
>>>      for unattended recovery tasks;
>>>    - update systems, where the splash client can offer a simple feedback
>>>      for unattended update tasks.
>> If plymouth cannot be used by embedded systems for some reason, then you
>> should work on a plymouth alternative.
> 
> Agreed. With an updater running in user space, that process should also 
> manage the display update. No need for this in the kernel.
> 
>>
>>> While the first seems the most obvious one, it was the second that acted
>>> as the driver, as in the past I had to implement a ugly workaround using
>>> a systemd generator to kickstart the initialization of a display and
>>> shave ~400ms of boot time.
>>>
>>> The last 2 usecase, instead, are the reason I dropped the "boot" part
>>> from bootsplash.
>>>
>>> == Implementation details ==
>>>
>>> The design is quite simple, with a kernel thread doing the heavylifting
>>> for the rendering part and some locking to protect interactions with it.
>>>
>>> The splash image is loaded using the firmware framework, with the client
>>> expecting to find a binary dump having the right dimensions (width and
>>> height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
>>> modeset, the client will for example search for a firmware named:
>>>
>>>     drm_splash_1920x1080_RG24.raw
>>>
>>> If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
>>> mechanism is used to let userspace load the appropriate image.
>>>
>>> == Testing ==
>>>
>>> Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
>>> display connected to a Beagleplay and on a ILI9341 SPI display connected
>>> to a i.MX93 FRDM board. All these platforms revealed different
>>> weaknesses that were hopefully removed.
>>>
>>> == Open points / issues ==
>>>
>>> The reason for this being an RFC is that there are several open points:
>>>
>>>    - Support for tiled connectors should be there, but has not been
>>>      tested. Any idea on how to test it?
>> Did you mean tiled formats?
>>
>>>    - I'm not entirely convinced that using the firmware framework to 
>>> load
>>>      the images is the right path. The idea behind it was to re-use the
>>>      compressed firmware support, but then I discovered it is not there
>>>      for built-in firmware.
>> Yeah, firmware loading for this has a few issues (being tedious to setup
>> for when built-in being one). I think just going the fbdev penguin road
>> is a better choice: you provide the path, and it's embedded in the
>> kernel directly.
>>
>>>    - Again on the firmware loading: CONFIG_LOADPIN would interfere with
>>>      sysfs loading.
>>>    - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
>>>      leading me to think it is de-facto deprecated. And still, uevents
>>>      for firmware loading seem frowned upon these days...
>>>    - Generating binary dumps for... basically any format is not so
>>>      straightforward. I crafted a Python tool with AI help which seems
>>>      to work quite well, but I honestly did not yet understood which is
>>>      the policy for AI-generated code inside the kernel, so it is not
>>>      included in this patch set. All client code is genuine, though.
>> BMP is simple enough to support so we should probably use that instead
>> of a custom format.
> 
> file /sys/firmware/acpi/bgrt/image
> /sys/firmware/acpi/bgrt/image: PC bitmap, Windows 3.x format, 768 x 256 
> x 24, image size 589824, cbSize 589878, bits offset 54
> 
> That should probably be the format for now unless your firmware uses 
> something else natively. Code for reading a BMP file can be found in the 
> efifb driver. [1]
> 
> [1] https://elixir.bootlin.com/linux/v6.17.5/source/drivers/video/fbdev/ 
> efifb.c#L24
> 
> Apart from the criticism for complexity, I do like the idea of having a 
> splash screen.
> 
> Best regards
> Thomas
> 
>>
>> Maxime
> 

Re: [PATCH RFC 0/3] Add splash DRM client

[Maxime Ripard]

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On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
> On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
> > > >    - a very simple progress bar, which can be driven through sysfs;
> > 
> > Once you have options to control these settings from user space, you
> > should do it in user space entirely. As Maxime suggested, please improve
> > plymouth for anything with animation.
> > 
> > > >    - a static image (optional).
> > 
> > Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
> > is a candidate for display, or the penguin or a custom image. Please
> > make it configurable by Kconfig. Again, if you need policy and
> > heuristics for deciding what to display, you better do this in user
> > space.
> 
> I'd actually argue that the static image from BGRT should be the preferred
> priority.  This can make for a nice hand off to Plymouth.
> 
> The (UEFI) BIOS already will show this image as soon as the GOP driver is
> loaded.  Bootloaders like GRUB by default will avoid showing anything or
> will overwrite with the exact same image in the same location.  This can let
> the kernel do the same, and then the moment Plymouth takes over it could do
> the same.

And BGRT isn't typically found on embedded systems at all, so I'm not
sure it's a sensible default, let alone a priority. At most a possible
fallback.

Maxime

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Re: [PATCH RFC 0/3] Add splash DRM client

[Mario Limonciello]

On 10/27/25 11:28 AM, Maxime Ripard wrote:
> On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
>> On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
>>>>>     - a very simple progress bar, which can be driven through sysfs;
>>>
>>> Once you have options to control these settings from user space, you
>>> should do it in user space entirely. As Maxime suggested, please improve
>>> plymouth for anything with animation.
>>>
>>>>>     - a static image (optional).
>>>
>>> Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
>>> is a candidate for display, or the penguin or a custom image. Please
>>> make it configurable by Kconfig. Again, if you need policy and
>>> heuristics for deciding what to display, you better do this in user
>>> space.
>>
>> I'd actually argue that the static image from BGRT should be the preferred
>> priority.  This can make for a nice hand off to Plymouth.
>>
>> The (UEFI) BIOS already will show this image as soon as the GOP driver is
>> loaded.  Bootloaders like GRUB by default will avoid showing anything or
>> will overwrite with the exact same image in the same location.  This can let
>> the kernel do the same, and then the moment Plymouth takes over it could do
>> the same.
> 
> And BGRT isn't typically found on embedded systems at all, so I'm not
> sure it's a sensible default, let alone a priority. At most a possible

There are certainly embedded machines using UEFI and that have a BGRT.

How about "Sensible default the top of the priority list if it exists"

Just like Plymouth will start out with graphical splash and fallback to 
text if problems.

Re: [PATCH RFC 0/3] Add splash DRM client

[Maxime Ripard]

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On Mon, Oct 27, 2025 at 11:31:06AM -0500, Mario Limonciello wrote:
> On 10/27/25 11:28 AM, Maxime Ripard wrote:
> > On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
> > > On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
> > > > > >     - a very simple progress bar, which can be driven through sysfs;
> > > > 
> > > > Once you have options to control these settings from user space, you
> > > > should do it in user space entirely. As Maxime suggested, please improve
> > > > plymouth for anything with animation.
> > > > 
> > > > > >     - a static image (optional).
> > > > 
> > > > Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
> > > > is a candidate for display, or the penguin or a custom image. Please
> > > > make it configurable by Kconfig. Again, if you need policy and
> > > > heuristics for deciding what to display, you better do this in user
> > > > space.
> > > 
> > > I'd actually argue that the static image from BGRT should be the preferred
> > > priority.  This can make for a nice hand off to Plymouth.
> > > 
> > > The (UEFI) BIOS already will show this image as soon as the GOP driver is
> > > loaded.  Bootloaders like GRUB by default will avoid showing anything or
> > > will overwrite with the exact same image in the same location.  This can let
> > > the kernel do the same, and then the moment Plymouth takes over it could do
> > > the same.
> > 
> > And BGRT isn't typically found on embedded systems at all, so I'm not
> > sure it's a sensible default, let alone a priority. At most a possible
> 
> There are certainly embedded machines using UEFI and that have a BGRT.

Yes, indeed, hence the "typically".

> How about "Sensible default the top of the priority list if it exists"

How about we don't tell contributors what their priorities must be?

Maxime

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Re: [PATCH RFC 0/3] Add splash DRM client

[Francesco Valla]

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Hi,

On Monday, 27 October 2025 at 11:09:56 Maxime Ripard <mripard@kernel.org> wrote:
> Hi,
> 
> On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
> > this patchset adds a new DRM client offering splash functionalities,
> > able to draw to screen:
> > 
> >   - a colored background;
> 
> So, I like that part, and we were recently discussing about this.
> 
> >   - a single-line text message, which can be set through sysfs or
> >     directly from the kernel command line;
> >   - a very simple progress bar, which can be driven through sysfs;
> >   - a static image (optional).
> 
> But there's no reason to have all that in the kernel, and we already
> have userspace components to do so (plymouth being the main "mainstream"
> one).
> 

I get that for the "text message" and "progress bar" parts. I still have
some uses for them, that however may not be adherent to upstream philosophy.

> > Once compiled inside the kernel, the client can be enabled through the
> > command line specifying the drm_client_lib.active=splash parameter.
> > 
> > == Motivation ==
> > 
> > The motivation behind this work is to offer to embedded system
> > developers a new path for a simple activation of the display(s)
> > connected to their system, with the following usecases:
> > 
> >   - bootsplash - possibly displaying even before init;
> >   - early activation of the display pipeline, in particular whenever one
> >     component of the pipeline (e.g.: a panel) takes a non-negligible
> >     time to initialize;
> >   - recovery systems, where the splash client can offer a simple feedback
> >     for unattended recovery tasks;
> >   - update systems, where the splash client can offer a simple feedback
> >     for unattended update tasks.
> 
> If plymouth cannot be used by embedded systems for some reason, then you
> should work on a plymouth alternative.
> 

Thing is: any possible alternative would still start after userspace has
been loaded, checked (in case of secure boot, which is ubiquitous now)
and initialized. This means, at least in my usecases, several hundreds of
milliseconds after userspace start, to be summed to the panel initialization
time.

> > While the first seems the most obvious one, it was the second that acted
> > as the driver, as in the past I had to implement a ugly workaround using
> > a systemd generator to kickstart the initialization of a display and
> > shave ~400ms of boot time.
> > 
> > The last 2 usecase, instead, are the reason I dropped the "boot" part
> > from bootsplash.
> > 
> > == Implementation details ==
> > 
> > The design is quite simple, with a kernel thread doing the heavylifting
> > for the rendering part and some locking to protect interactions with it.
> > 
> > The splash image is loaded using the firmware framework, with the client
> > expecting to find a binary dump having the right dimensions (width and
> > height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
> > modeset, the client will for example search for a firmware named:
> > 
> >    drm_splash_1920x1080_RG24.raw
> > 
> > If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
> > mechanism is used to let userspace load the appropriate image.
> > 
> > == Testing ==
> > 
> > Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
> > display connected to a Beagleplay and on a ILI9341 SPI display connected
> > to a i.MX93 FRDM board. All these platforms revealed different
> > weaknesses that were hopefully removed.
> > 
> > == Open points / issues ==
> > 
> > The reason for this being an RFC is that there are several open points:
> > 
> >   - Support for tiled connectors should be there, but has not been
> >     tested. Any idea on how to test it?
> 
> Did you mean tiled formats?
> 

No, AFAIU the tiled connectors are different connectors that feed different
panels, which however are part of a single logical screen. Support for this
setup is present at drm level [1], but I'm not familiar with it.

I've only found this used inside the i915 Intel driver [2].

> >   - I'm not entirely convinced that using the firmware framework to load
> >     the images is the right path. The idea behind it was to re-use the
> >     compressed firmware support, but then I discovered it is not there
> >     for built-in firmware.
> 
> Yeah, firmware loading for this has a few issues (being tedious to setup
> for when built-in being one). I think just going the fbdev penguin road
> is a better choice: you provide the path, and it's embedded in the
> kernel directly.
> 

Yes, this is already working, but if large-ish images are used, the loading
time for them defeats the entire purpose of an in-kernel splash.

> >   - Again on the firmware loading: CONFIG_LOADPIN would interfere with
> >     sysfs loading.
> >   - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
> >     leading me to think it is de-facto deprecated. And still, uevents
> >     for firmware loading seem frowned upon these days... 
> >   - Generating binary dumps for... basically any format is not so
> >     straightforward. I crafted a Python tool with AI help which seems
> >     to work quite well, but I honestly did not yet understood which is
> >     the policy for AI-generated code inside the kernel, so it is not
> >     included in this patch set. All client code is genuine, though.
> 
> BMP is simple enough to support so we should probably use that instead
> of a custom format.
> 
> Maxime
> 


Thank you!

Regards,
Francesco


[1] https://elixir.bootlin.com/linux/v6.17.5/source/include/drm/drm_connector.h#L2253
[2] https://elixir.bootlin.com/linux/v6.17.5/source/drivers/gpu/drm/drm_connector.c#L2739


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Re: [PATCH RFC 0/3] Add splash DRM client

[Francesco Valla]

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Hi Thomas,

On Monday, 27 October 2025 at 13:35:31 Thomas Zimmermann <tzimmermann@suse.de> wrote:
> Hi Francenso, Maxime,
> 
> Am 27.10.25 um 11:09 schrieb Maxime Ripard:
> > Hi,
> >
> > On Mon, Oct 27, 2025 at 12:03:00AM +0100, Francesco Valla wrote:
> >> this patchset adds a new DRM client offering splash functionalities,
> >> able to draw to screen:
> >>
> >>    - a colored background;
> > So, I like that part, and we were recently discussing about this.
> 
> The panic screen has configurable foreground/background colors. Maybe we 
> can harmonize these settings.
> 

Maybe, but probably the panic colors would typically be much more vibrant
than splash ones. 

> >
> >>    - a single-line text message, which can be set through sysfs or
> >>      directly from the kernel command line;
> 
> Put it into the kernel config.
> 
> >>    - a very simple progress bar, which can be driven through sysfs;
> 
> Once you have options to control these settings from user space, you 
> should do it in user space entirely. As Maxime suggested, please improve 
> plymouth for anything with animation.
> 

On this I can agree, see my reply to Maxime.

> >>    - a static image (optional).
> 
> Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This 
> is a candidate for display, or the penguin or a custom image. Please 
> make it configurable by Kconfig. Again, if you need policy and 
> heuristics for deciding what to display, you better do this in user space.
>

I'm not under ACPI/UEFI typically, and the concept for this patch was not
developed on such system. But I'll take a look!

> > But there's no reason to have all that in the kernel, and we already
> > have userspace components to do so (plymouth being the main "mainstream"
> > one).
> >
> >> Once compiled inside the kernel, the client can be enabled through the
> >> command line specifying the drm_client_lib.active=splash parameter.
> >>
> >> == Motivation ==
> >>
> >> The motivation behind this work is to offer to embedded system
> >> developers a new path for a simple activation of the display(s)
> >> connected to their system, with the following usecases:
> >>
> >>    - bootsplash - possibly displaying even before init;
> >>    - early activation of the display pipeline, in particular whenever one
> >>      component of the pipeline (e.g.: a panel) takes a non-negligible
> >>      time to initialize;
> >>    - recovery systems, where the splash client can offer a simple feedback
> >>      for unattended recovery tasks;
> >>    - update systems, where the splash client can offer a simple feedback
> >>      for unattended update tasks.
> > If plymouth cannot be used by embedded systems for some reason, then you
> > should work on a plymouth alternative.
> 
> Agreed. With an updater running in user space, that process should also 
> manage the display update. No need for this in the kernel.
> 
> >
> >> While the first seems the most obvious one, it was the second that acted
> >> as the driver, as in the past I had to implement a ugly workaround using
> >> a systemd generator to kickstart the initialization of a display and
> >> shave ~400ms of boot time.
> >>
> >> The last 2 usecase, instead, are the reason I dropped the "boot" part
> >> from bootsplash.
> >>
> >> == Implementation details ==
> >>
> >> The design is quite simple, with a kernel thread doing the heavylifting
> >> for the rendering part and some locking to protect interactions with it.
> >>
> >> The splash image is loaded using the firmware framework, with the client
> >> expecting to find a binary dump having the right dimensions (width and
> >> height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
> >> modeset, the client will for example search for a firmware named:
> >>
> >>     drm_splash_1920x1080_RG24.raw
> >>
> >> If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
> >> mechanism is used to let userspace load the appropriate image.
> >>
> >> == Testing ==
> >>
> >> Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
> >> display connected to a Beagleplay and on a ILI9341 SPI display connected
> >> to a i.MX93 FRDM board. All these platforms revealed different
> >> weaknesses that were hopefully removed.
> >>
> >> == Open points / issues ==
> >>
> >> The reason for this being an RFC is that there are several open points:
> >>
> >>    - Support for tiled connectors should be there, but has not been
> >>      tested. Any idea on how to test it?
> > Did you mean tiled formats?
> >
> >>    - I'm not entirely convinced that using the firmware framework to load
> >>      the images is the right path. The idea behind it was to re-use the
> >>      compressed firmware support, but then I discovered it is not there
> >>      for built-in firmware.
> > Yeah, firmware loading for this has a few issues (being tedious to setup
> > for when built-in being one). I think just going the fbdev penguin road
> > is a better choice: you provide the path, and it's embedded in the
> > kernel directly.
> >
> >>    - Again on the firmware loading: CONFIG_LOADPIN would interfere with
> >>      sysfs loading.
> >>    - And again: FW_ACTION_NOUEVENT only has one user inside the kernel,
> >>      leading me to think it is de-facto deprecated. And still, uevents
> >>      for firmware loading seem frowned upon these days...
> >>    - Generating binary dumps for... basically any format is not so
> >>      straightforward. I crafted a Python tool with AI help which seems
> >>      to work quite well, but I honestly did not yet understood which is
> >>      the policy for AI-generated code inside the kernel, so it is not
> >>      included in this patch set. All client code is genuine, though.
> > BMP is simple enough to support so we should probably use that instead
> > of a custom format.
> 
> file /sys/firmware/acpi/bgrt/image
> /sys/firmware/acpi/bgrt/image: PC bitmap, Windows 3.x format, 768 x 256 
> x 24, image size 589824, cbSize 589878, bits offset 54
> 
> That should probably be the format for now unless your firmware uses 
> something else natively. Code for reading a BMP file can be found in the 
> efifb driver. [1]
> 
> [1] 
> https://elixir.bootlin.com/linux/v6.17.5/source/drivers/video/fbdev/efifb.c#L24
> 

When I started working on the patch I was not able to find this BMP decoder,
I only found the PPM one from the bootup logo. I'll take a look here too.  


> Apart from the criticism for complexity, I do like the idea of having a 
> splash screen.
> 
> Best regards
> Thomas
> 
> >
> > Maxime
> 
> 

Thank you!

Best regards,
Francesco

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Re: [PATCH RFC 0/3] Add splash DRM client

[Francesco Valla]

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Hi,

On Monday, 27 October 2025 at 18:19:12 Maxime Ripard <mripard@kernel.org> wrote:
> On Mon, Oct 27, 2025 at 11:31:06AM -0500, Mario Limonciello wrote:
> > On 10/27/25 11:28 AM, Maxime Ripard wrote:
> > > On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
> > > > On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
> > > > > > >     - a very simple progress bar, which can be driven through sysfs;
> > > > > 
> > > > > Once you have options to control these settings from user space, you
> > > > > should do it in user space entirely. As Maxime suggested, please improve
> > > > > plymouth for anything with animation.
> > > > > 
> > > > > > >     - a static image (optional).
> > > > > 
> > > > > Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
> > > > > is a candidate for display, or the penguin or a custom image. Please
> > > > > make it configurable by Kconfig. Again, if you need policy and
> > > > > heuristics for deciding what to display, you better do this in user
> > > > > space.
> > > > 
> > > > I'd actually argue that the static image from BGRT should be the preferred
> > > > priority.  This can make for a nice hand off to Plymouth.
> > > > 
> > > > The (UEFI) BIOS already will show this image as soon as the GOP driver is
> > > > loaded.  Bootloaders like GRUB by default will avoid showing anything or
> > > > will overwrite with the exact same image in the same location.  This can let
> > > > the kernel do the same, and then the moment Plymouth takes over it could do
> > > > the same.
> > > 
> > > And BGRT isn't typically found on embedded systems at all, so I'm not
> > > sure it's a sensible default, let alone a priority. At most a possible
> > 
> > There are certainly embedded machines using UEFI and that have a BGRT.
> 
> Yes, indeed, hence the "typically".
> 
> > How about "Sensible default the top of the priority list if it exists"
> 
> How about we don't tell contributors what their priorities must be?
> 
> Maxime
> 

I'm not familiar at all with BGRT, I'll study a bit about it.

A build-time configuration could then let the user select:

- a plain solid color
- a custom static image
- the penguin logo (?)
- (on UEFI systems) BGRT source



Thank you

Regards,
Francesco

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Re: [PATCH RFC 0/3] Add splash DRM client

[Mario Limonciello]

On 10/28/25 3:09 AM, Francesco Valla wrote:
> Hi,
> 
> On Monday, 27 October 2025 at 18:19:12 Maxime Ripard <mripard@kernel.org> wrote:
>> On Mon, Oct 27, 2025 at 11:31:06AM -0500, Mario Limonciello wrote:
>>> On 10/27/25 11:28 AM, Maxime Ripard wrote:
>>>> On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
>>>>> On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
>>>>>>>>      - a very simple progress bar, which can be driven through sysfs;
>>>>>>
>>>>>> Once you have options to control these settings from user space, you
>>>>>> should do it in user space entirely. As Maxime suggested, please improve
>>>>>> plymouth for anything with animation.
>>>>>>
>>>>>>>>      - a static image (optional).
>>>>>>
>>>>>> Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
>>>>>> is a candidate for display, or the penguin or a custom image. Please
>>>>>> make it configurable by Kconfig. Again, if you need policy and
>>>>>> heuristics for deciding what to display, you better do this in user
>>>>>> space.
>>>>>
>>>>> I'd actually argue that the static image from BGRT should be the preferred
>>>>> priority.  This can make for a nice hand off to Plymouth.
>>>>>
>>>>> The (UEFI) BIOS already will show this image as soon as the GOP driver is
>>>>> loaded.  Bootloaders like GRUB by default will avoid showing anything or
>>>>> will overwrite with the exact same image in the same location.  This can let
>>>>> the kernel do the same, and then the moment Plymouth takes over it could do
>>>>> the same.
>>>>
>>>> And BGRT isn't typically found on embedded systems at all, so I'm not
>>>> sure it's a sensible default, let alone a priority. At most a possible
>>>
>>> There are certainly embedded machines using UEFI and that have a BGRT.
>>
>> Yes, indeed, hence the "typically".
>>
>>> How about "Sensible default the top of the priority list if it exists"
>>
>> How about we don't tell contributors what their priorities must be?
>>
>> Maxime
>>
> 
> I'm not familiar at all with BGRT, I'll study a bit about it.
> 
> A build-time configuration could then let the user select:
> 
> - a plain solid color
> - a custom static image
> - the penguin logo (?)
> - (on UEFI systems) BGRT source

Thanks!

What I had in mind (which feel free to disagree - it's an RC afterall):

User can pick one of these:

CONFIG_SPLASH_IMAGE
CONFIG_SPLASH_COLOR

If user picks CONFIG_SPLASH_IMAGE then the default behavior would be 
UEFI BGRT with a fallback to a Linux penguin.

Additionally there could be a

CONFIG_SPLASH_CUSTOM_IMAGE

This would populate the path to a custom image at build time.

If user picks this then it would override both UEFI BGRT and Linux penguin.

> 
> 
> 
> Thank you
> 
> Regards,
> Francesco

Re: [PATCH RFC 0/3] Add splash DRM client

[Maxime Ripard]

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On Tue, Oct 28, 2025 at 08:58:05AM +0100, Francesco Valla wrote:
> On Monday, 27 October 2025 at 11:09:56 Maxime Ripard <mripard@kernel.org> wrote:
> > > Once compiled inside the kernel, the client can be enabled through the
> > > command line specifying the drm_client_lib.active=splash parameter.
> > > 
> > > == Motivation ==
> > > 
> > > The motivation behind this work is to offer to embedded system
> > > developers a new path for a simple activation of the display(s)
> > > connected to their system, with the following usecases:
> > > 
> > >   - bootsplash - possibly displaying even before init;
> > >   - early activation of the display pipeline, in particular whenever one
> > >     component of the pipeline (e.g.: a panel) takes a non-negligible
> > >     time to initialize;
> > >   - recovery systems, where the splash client can offer a simple feedback
> > >     for unattended recovery tasks;
> > >   - update systems, where the splash client can offer a simple feedback
> > >     for unattended update tasks.
> > 
> > If plymouth cannot be used by embedded systems for some reason, then you
> > should work on a plymouth alternative.
>
> Thing is: any possible alternative would still start after userspace has
> been loaded, checked (in case of secure boot, which is ubiquitous now)
> and initialized. This means, at least in my usecases, several hundreds of
> milliseconds after userspace start, to be summed to the panel initialization
> time.

Yeah, but you have a *lot* of policies even for something as simple as a
bootsplash:

  * Do you want it on all your screens or just one, if so, which one?

  * If the bootsplash image doesn't fit the screen you chose, what
    should you do? stretch, crop, keep the same resolution? If the image
    is smaller than the screen, where do you want to put it? Top left
    corner? In the center?

  * If there's BGRT, do you want to have BGRT always, bootsplash always,
    compose the bootsplash with BGRT? If so, same questions than before.

etc.

The kernel can't answer all these questions, and can't address every
possible use case. Userspace can, and that's largely why plymouth
exists.

But If the main thing you care about is boot time, U-Boot has everything
needed to setup a bootsplash early.

> > > While the first seems the most obvious one, it was the second that acted
> > > as the driver, as in the past I had to implement a ugly workaround using
> > > a systemd generator to kickstart the initialization of a display and
> > > shave ~400ms of boot time.
> > > 
> > > The last 2 usecase, instead, are the reason I dropped the "boot" part
> > > from bootsplash.
> > > 
> > > == Implementation details ==
> > > 
> > > The design is quite simple, with a kernel thread doing the heavylifting
> > > for the rendering part and some locking to protect interactions with it.
> > > 
> > > The splash image is loaded using the firmware framework, with the client
> > > expecting to find a binary dump having the right dimensions (width and
> > > height) and FOURCC format for each modeset. Given a 1920x1080 RGB888
> > > modeset, the client will for example search for a firmware named:
> > > 
> > >    drm_splash_1920x1080_RG24.raw
> > > 
> > > If the firmware cannot be loaded directly, the NOUEVENT sysfs fallback
> > > mechanism is used to let userspace load the appropriate image.
> > > 
> > > == Testing ==
> > > 
> > > Testing was done on qemu (both with vkms and bochs drivers), on a HDMI
> > > display connected to a Beagleplay and on a ILI9341 SPI display connected
> > > to a i.MX93 FRDM board. All these platforms revealed different
> > > weaknesses that were hopefully removed.
> > > 
> > > == Open points / issues ==
> > > 
> > > The reason for this being an RFC is that there are several open points:
> > > 
> > >   - Support for tiled connectors should be there, but has not been
> > >     tested. Any idea on how to test it?
> > 
> > Did you mean tiled formats?
> > 
> 
> No, AFAIU the tiled connectors are different connectors that feed different
> panels, which however are part of a single logical screen. Support for this
> setup is present at drm level [1], but I'm not familiar with it.
> 
> I've only found this used inside the i915 Intel driver [2].

TIL, thanks.

> > >   - I'm not entirely convinced that using the firmware framework to load
> > >     the images is the right path. The idea behind it was to re-use the
> > >     compressed firmware support, but then I discovered it is not there
> > >     for built-in firmware.
> > 
> > Yeah, firmware loading for this has a few issues (being tedious to setup
> > for when built-in being one). I think just going the fbdev penguin road
> > is a better choice: you provide the path, and it's embedded in the
> > kernel directly.
> > 
> 
> Yes, this is already working, but if large-ish images are used, the loading
> time for them defeats the entire purpose of an in-kernel splash.

The loading time of what exactly? If the image is in some section of the
binary, you wouldn't have to load anything.

Maxime

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Re: [PATCH RFC 0/3] Add splash DRM client

[Maxime Ripard]

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On Tue, Oct 28, 2025 at 09:09:06AM +0100, Francesco Valla wrote:
> Hi,
> 
> On Monday, 27 October 2025 at 18:19:12 Maxime Ripard <mripard@kernel.org> wrote:
> > On Mon, Oct 27, 2025 at 11:31:06AM -0500, Mario Limonciello wrote:
> > > On 10/27/25 11:28 AM, Maxime Ripard wrote:
> > > > On Mon, Oct 27, 2025 at 11:01:55AM -0500, Mario Limonciello wrote:
> > > > > On 10/27/25 7:35 AM, Thomas Zimmermann wrote:
> > > > > > > >     - a very simple progress bar, which can be driven through sysfs;
> > > > > > 
> > > > > > Once you have options to control these settings from user space, you
> > > > > > should do it in user space entirely. As Maxime suggested, please improve
> > > > > > plymouth for anything with animation.
> > > > > > 
> > > > > > > >     - a static image (optional).
> > > > > > 
> > > > > > Board vendors often provide an image, see /sys/firmware/acpi/bgrt/. This
> > > > > > is a candidate for display, or the penguin or a custom image. Please
> > > > > > make it configurable by Kconfig. Again, if you need policy and
> > > > > > heuristics for deciding what to display, you better do this in user
> > > > > > space.
> > > > > 
> > > > > I'd actually argue that the static image from BGRT should be the preferred
> > > > > priority.  This can make for a nice hand off to Plymouth.
> > > > > 
> > > > > The (UEFI) BIOS already will show this image as soon as the GOP driver is
> > > > > loaded.  Bootloaders like GRUB by default will avoid showing anything or
> > > > > will overwrite with the exact same image in the same location.  This can let
> > > > > the kernel do the same, and then the moment Plymouth takes over it could do
> > > > > the same.
> > > > 
> > > > And BGRT isn't typically found on embedded systems at all, so I'm not
> > > > sure it's a sensible default, let alone a priority. At most a possible
> > > 
> > > There are certainly embedded machines using UEFI and that have a BGRT.
> > 
> > Yes, indeed, hence the "typically".
> > 
> > > How about "Sensible default the top of the priority list if it exists"
> > 
> > How about we don't tell contributors what their priorities must be?
> > 
> > Maxime
> > 
> 
> I'm not familiar at all with BGRT, I'll study a bit about it.
> 
> A build-time configuration could then let the user select:
> 
> - a plain solid color
> - a custom static image
> - the penguin logo (?)
> - (on UEFI systems) BGRT source

It wouldn't work for generic distros that would run with the same config
on systems with and without BGRT.

Again, that whole discussion around BGRT is very premature, I'd suggest
to drop it for now.

Maxime

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