Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

6 files changed, 885 insertions, 0 deletions

diff --git a/drivers/gpu/drm/clients/Kconfig b/drivers/gpu/drm/clients/Kconfig
new file mode 100644
index 000000000..6096c623d
--- /dev/null
+++ b/drivers/gpu/drm/clients/Kconfig
@@ -0,0 +1,123 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config DRM_CLIENT_LIB
+	tristate
+	depends on DRM
+	select DRM_KMS_HELPER if DRM_FBDEV_EMULATION
+	select FB_CORE if DRM_FBDEV_EMULATION
+	help
+	  This option enables the DRM client library and selects all
+	  modules and components according to the enabled clients.
+
+config DRM_CLIENT_SELECTION
+	tristate
+	depends on DRM
+	select DRM_CLIENT_LIB if DRM_CLIENT_LOG
+	select DRM_CLIENT_LIB if DRM_FBDEV_EMULATION
+	help
+	  Drivers that support in-kernel DRM clients have to select this
+	  option.
+
+config DRM_CLIENT_SETUP
+	bool
+	depends on DRM_CLIENT_SELECTION
+	help
+	  Enables the DRM client selection. DRM drivers that support the
+	  default clients should select DRM_CLIENT_SELECTION instead.
+
+menu "Supported DRM clients"
+	depends on DRM_CLIENT_SELECTION
+
+config DRM_FBDEV_EMULATION
+	bool "Enable legacy fbdev support for your modesetting driver"
+	depends on DRM_CLIENT_SELECTION
+	select DRM_CLIENT
+	select DRM_CLIENT_SETUP
+	select FRAMEBUFFER_CONSOLE_DETECT_PRIMARY if FRAMEBUFFER_CONSOLE
+	default FB
+	help
+	  Choose this option if you have a need for the legacy fbdev
+	  support. Note that this support also provides the linux console
+	  support on top of your modesetting driver.
+
+	  If in doubt, say "Y".
+
+config DRM_FBDEV_OVERALLOC
+	int "Overallocation of the fbdev buffer"
+	depends on DRM_FBDEV_EMULATION
+	default 100
+	help
+	  Defines the fbdev buffer overallocation in percent. Default
+	  is 100. Typical values for double buffering will be 200,
+	  triple buffering 300.
+
+config DRM_FBDEV_LEAK_PHYS_SMEM
+	bool "Shamelessly allow leaking of fbdev physical address (DANGEROUS)"
+	depends on DRM_FBDEV_EMULATION && EXPERT
+	default n
+	help
+	  In order to keep user-space compatibility, we want in certain
+	  use-cases to keep leaking the fbdev physical address to the
+	  user-space program handling the fbdev buffer.
+	  This affects, not only, Amlogic, Allwinner or Rockchip devices
+	  with ARM Mali GPUs using a userspace Blob.
+	  This option is not supported by upstream developers and should be
+	  removed as soon as possible and be considered as a broken and
+	  legacy behaviour from a modern fbdev device driver.
+
+	  Please send any bug reports when using this to your proprietary
+	  software vendor that requires this.
+
+	  If in doubt, say "N" or spread the word to your closed source
+	  library vendor.
+
+config DRM_CLIENT_LOG
+	bool "Print the kernel boot message on the screen"
+	depends on DRM_CLIENT_SELECTION
+	select DRM_CLIENT
+	select DRM_CLIENT_SETUP
+	select DRM_DRAW
+	select FONT_SUPPORT
+	help
+	  This enable a drm logger, that will print the kernel messages to the
+	  screen until the userspace is ready to take over.
+
+	  If you only need logs, but no terminal, or if you prefer userspace
+	  terminal, say "Y".
+
+choice
+	prompt "Default DRM Client"
+	depends on DRM_CLIENT_SELECTION
+	depends on DRM_FBDEV_EMULATION || DRM_CLIENT_LOG
+	default DRM_CLIENT_DEFAULT_FBDEV
+	help
+	  Selects the default drm client.
+
+	  The selection made here can be overridden by using the kernel
+	  command line 'drm_client_lib.active=fbdev' option.
+
+config DRM_CLIENT_DEFAULT_FBDEV
+	bool "fbdev"
+	depends on DRM_FBDEV_EMULATION
+	help
+	  Use fbdev emulation as default drm client. This is needed to have
+	  fbcon on top of a drm driver.
+
+config DRM_CLIENT_DEFAULT_LOG
+	bool "log"
+	depends on DRM_CLIENT_LOG
+	help
+	  Use drm log as default drm client. This will display boot logs on the
+	  screen, but doesn't implement a full terminal. For that you will need
+	  a userspace terminal using drm/kms.
+
+endchoice
+
+config DRM_CLIENT_DEFAULT
+       string
+       depends on DRM_CLIENT
+       default "fbdev" if DRM_CLIENT_DEFAULT_FBDEV
+       default "log" if DRM_CLIENT_DEFAULT_LOG
+       default ""
+
+endmenu
diff --git a/drivers/gpu/drm/clients/Makefile b/drivers/gpu/drm/clients/Makefile
new file mode 100644
index 000000000..c16addbc3
--- /dev/null
+++ b/drivers/gpu/drm/clients/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+
+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-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fbdev_client.o
+obj-$(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
new file mode 100644
index 000000000..6dc078bf6
--- /dev/null
+++ b/drivers/gpu/drm/clients/drm_client_internal.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef DRM_CLIENT_INTERNAL_H
+#define DRM_CLIENT_INTERNAL_H
+
+struct drm_device;
+struct drm_format_info;
+
+#ifdef CONFIG_DRM_FBDEV_EMULATION
+int drm_fbdev_client_setup(struct drm_device *dev, const struct drm_format_info *format);
+#else
+static inline int drm_fbdev_client_setup(struct drm_device *dev,
+					 const struct drm_format_info *format)
+{
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_DRM_CLIENT_LOG
+void drm_log_register(struct drm_device *dev);
+#else
+static inline void drm_log_register(struct drm_device *dev) {}
+#endif
+
+#endif
diff --git a/drivers/gpu/drm/clients/drm_client_setup.c b/drivers/gpu/drm/clients/drm_client_setup.c
new file mode 100644
index 000000000..515aceac2
--- /dev/null
+++ b/drivers/gpu/drm/clients/drm_client_setup.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: MIT
+
+#include <linux/export.h>
+
+#include <drm/clients/drm_client_setup.h>
+#include <drm/drm_device.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_print.h>
+
+#include "drm_client_internal.h"
+
+static char drm_client_default[16] = CONFIG_DRM_CLIENT_DEFAULT;
+module_param_string(active, drm_client_default, sizeof(drm_client_default), 0444);
+MODULE_PARM_DESC(active,
+		 "Choose which drm client to start, default is "
+		 CONFIG_DRM_CLIENT_DEFAULT);
+
+/**
+ * drm_client_setup() - Setup in-kernel DRM clients
+ * @dev: DRM device
+ * @format: Preferred pixel format for the device. Use NULL, unless
+ *          there is clearly a driver-preferred format.
+ *
+ * This function sets up the in-kernel DRM clients. Restore, hotplug
+ * events and teardown are all taken care of.
+ *
+ * Drivers should call drm_client_setup() after registering the new
+ * DRM device with drm_dev_register(). This function is safe to call
+ * even when there are no connectors present. Setup will be retried
+ * on the next hotplug event.
+ *
+ * The clients are destroyed by drm_dev_unregister().
+ */
+void drm_client_setup(struct drm_device *dev, const struct drm_format_info *format)
+{
+	if (!drm_core_check_feature(dev, DRIVER_MODESET)) {
+		drm_dbg(dev, "driver does not support mode-setting, skipping DRM clients\n");
+		return;
+	}
+
+#ifdef CONFIG_DRM_FBDEV_EMULATION
+	if (!strcmp(drm_client_default, "fbdev")) {
+		int ret;
+
+		ret = drm_fbdev_client_setup(dev, format);
+		if (ret)
+			drm_warn(dev, "Failed to set up DRM client; error %d\n", ret);
+		return;
+	}
+#endif
+
+#ifdef CONFIG_DRM_CLIENT_LOG
+	if (!strcmp(drm_client_default, "log")) {
+		drm_log_register(dev);
+		return;
+	}
+#endif
+	if (strcmp(drm_client_default, ""))
+		drm_warn(dev, "Unknown DRM client %s\n", drm_client_default);
+}
+EXPORT_SYMBOL(drm_client_setup);
+
+/**
+ * drm_client_setup_with_fourcc() - Setup in-kernel DRM clients for color mode
+ * @dev: DRM device
+ * @fourcc: Preferred pixel format as 4CC code for the device
+ *
+ * This function sets up the in-kernel DRM clients. It is equivalent
+ * to drm_client_setup(), but expects a 4CC code as second argument.
+ */
+void drm_client_setup_with_fourcc(struct drm_device *dev, u32 fourcc)
+{
+	drm_client_setup(dev, drm_format_info(fourcc));
+}
+EXPORT_SYMBOL(drm_client_setup_with_fourcc);
+
+/**
+ * drm_client_setup_with_color_mode() - Setup in-kernel DRM clients for color mode
+ * @dev: DRM device
+ * @color_mode: Preferred color mode for the device
+ *
+ * This function sets up the in-kernel DRM clients. It is equivalent
+ * to drm_client_setup(), but expects a color mode as second argument.
+ *
+ * Do not use this function in new drivers. Prefer drm_client_setup() with a
+ * format of NULL.
+ */
+void drm_client_setup_with_color_mode(struct drm_device *dev, unsigned int color_mode)
+{
+	u32 fourcc = drm_driver_color_mode_format(dev, color_mode);
+
+	drm_client_setup_with_fourcc(dev, fourcc);
+}
+EXPORT_SYMBOL(drm_client_setup_with_color_mode);
+
+MODULE_DESCRIPTION("In-kernel DRM clients");
+MODULE_LICENSE("GPL and additional rights");
diff --git a/drivers/gpu/drm/clients/drm_fbdev_client.c b/drivers/gpu/drm/clients/drm_fbdev_client.c
new file mode 100644
index 000000000..91d196a39
--- /dev/null
+++ b/drivers/gpu/drm/clients/drm_fbdev_client.c
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: MIT
+
+#include <drm/drm_client.h>
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fb_helper.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_print.h>
+
+#include "drm_client_internal.h"
+
+/*
+ * struct drm_client_funcs
+ */
+
+static void drm_fbdev_client_free(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+}
+
+static void drm_fbdev_client_unregister(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	if (fb_helper->info) {
+		/*
+		 * Fully probed framebuffer device
+		 */
+		drm_fb_helper_unregister_info(fb_helper);
+	} else {
+		/*
+		 * Partially initialized client, no framebuffer device yet
+		 */
+		drm_client_release(&fb_helper->client);
+	}
+}
+
+static int drm_fbdev_client_restore(struct drm_client_dev *client, bool force)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper, force);
+
+	return 0;
+}
+
+static int drm_fbdev_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+	struct drm_device *dev = client->dev;
+	int ret;
+
+	if (dev->fb_helper)
+		return drm_fb_helper_hotplug_event(dev->fb_helper);
+
+	ret = drm_fb_helper_init(dev, fb_helper);
+	if (ret)
+		goto err_drm_err;
+
+	if (!drm_drv_uses_atomic_modeset(dev))
+		drm_helper_disable_unused_functions(dev);
+
+	ret = drm_fb_helper_initial_config(fb_helper);
+	if (ret)
+		goto err_drm_fb_helper_fini;
+
+	return 0;
+
+err_drm_fb_helper_fini:
+	drm_fb_helper_fini(fb_helper);
+err_drm_err:
+	drm_err(dev, "fbdev: Failed to setup emulation (ret=%d)\n", ret);
+	return ret;
+}
+
+static int drm_fbdev_client_suspend(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	drm_fb_helper_set_suspend_unlocked(fb_helper, true);
+
+	return 0;
+}
+
+static int drm_fbdev_client_resume(struct drm_client_dev *client)
+{
+	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
+
+	drm_fb_helper_set_suspend_unlocked(fb_helper, false);
+
+	return 0;
+}
+
+static const struct drm_client_funcs drm_fbdev_client_funcs = {
+	.owner		= THIS_MODULE,
+	.free		= drm_fbdev_client_free,
+	.unregister	= drm_fbdev_client_unregister,
+	.restore	= drm_fbdev_client_restore,
+	.hotplug	= drm_fbdev_client_hotplug,
+	.suspend	= drm_fbdev_client_suspend,
+	.resume		= drm_fbdev_client_resume,
+};
+
+/**
+ * drm_fbdev_client_setup() - Setup fbdev emulation
+ * @dev: DRM device
+ * @format: Preferred color format for the device. DRM_FORMAT_XRGB8888
+ *          is used if this is zero.
+ *
+ * This function sets up fbdev emulation. Restore, hotplug events and
+ * teardown are all taken care of. Drivers that do suspend/resume need
+ * to call drm_client_dev_suspend() and drm_client_dev_resume() by
+ * themselves. Simple drivers might use drm_mode_config_helper_suspend().
+ *
+ * This function is safe to call even when there are no connectors present.
+ * Setup will be retried on the next hotplug event.
+ *
+ * The fbdev client is destroyed by drm_dev_unregister().
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
+ */
+int drm_fbdev_client_setup(struct drm_device *dev, const struct drm_format_info *format)
+{
+	struct drm_fb_helper *fb_helper;
+	unsigned int color_mode;
+	int ret;
+
+	/* TODO: Use format info throughout DRM */
+	if (format) {
+		unsigned int bpp = drm_format_info_bpp(format, 0);
+
+		switch (bpp) {
+		case 16:
+			color_mode = format->depth; // could also be 15
+			break;
+		default:
+			color_mode = bpp;
+		}
+	} else {
+		switch (dev->mode_config.preferred_depth) {
+		case 0:
+		case 24:
+			color_mode = 32;
+			break;
+		default:
+			color_mode = dev->mode_config.preferred_depth;
+		}
+	}
+
+	drm_WARN(dev, !dev->registered, "Device has not been registered.\n");
+	drm_WARN(dev, dev->fb_helper, "fb_helper is already set!\n");
+
+	fb_helper = kzalloc_obj(*fb_helper);
+	if (!fb_helper)
+		return -ENOMEM;
+	drm_fb_helper_prepare(dev, fb_helper, color_mode, NULL);
+
+	ret = drm_client_init(dev, &fb_helper->client, "fbdev", &drm_fbdev_client_funcs);
+	if (ret) {
+		drm_err(dev, "Failed to register client: %d\n", ret);
+		goto err_drm_client_init;
+	}
+
+	drm_client_register(&fb_helper->client);
+
+	return 0;
+
+err_drm_client_init:
+	drm_fb_helper_unprepare(fb_helper);
+	kfree(fb_helper);
+	return ret;
+}
diff --git a/drivers/gpu/drm/clients/drm_log.c b/drivers/gpu/drm/clients/drm_log.c
new file mode 100644
index 000000000..99062609d
--- /dev/null
+++ b/drivers/gpu/drm/clients/drm_log.c
@@ -0,0 +1,455 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/*
+ * Copyright (c) 2024 Red Hat.
+ * Author: Jocelyn Falempe <jfalempe@redhat.com>
+ */
+
+#include <linux/console.h>
+#include <linux/font.h>
+#include <linux/init.h>
+#include <linux/iosys-map.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_print.h>
+
+#include "drm_client_internal.h"
+#include "drm_draw_internal.h"
+#include "drm_internal.h"
+
+MODULE_AUTHOR("Jocelyn Falempe");
+MODULE_DESCRIPTION("DRM boot logger");
+MODULE_LICENSE("GPL");
+
+static unsigned int scale = 1;
+module_param(scale, uint, 0444);
+MODULE_PARM_DESC(scale, "Integer scaling factor for drm_log, default is 1");
+
+/**
+ * DOC: overview
+ *
+ * This is a simple graphic logger, to print the kernel message on screen, until
+ * a userspace application is able to take over.
+ * It is only for debugging purpose.
+ */
+
+struct drm_log_scanout {
+	struct drm_client_buffer *buffer;
+	const struct font_desc *font;
+	u32 rows;
+	u32 columns;
+	u32 scaled_font_h;
+	u32 scaled_font_w;
+	u32 line;
+	u32 format;
+	u32 px_width;
+	u32 front_color;
+	u32 prefix_color;
+};
+
+struct drm_log {
+	struct mutex lock;
+	struct drm_client_dev client;
+	struct console con;
+	bool probed;
+	u32 n_scanout;
+	struct drm_log_scanout *scanout;
+};
+
+static struct drm_log *client_to_drm_log(struct drm_client_dev *client)
+{
+	return container_of(client, struct drm_log, client);
+}
+
+static struct drm_log *console_to_drm_log(struct console *con)
+{
+	return container_of(con, struct drm_log, con);
+}
+
+static void drm_log_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, scale, color);
+		break;
+	case 3:
+		drm_draw_blit24(dst, dst_pitch, src, src_pitch, height, width, scale, color);
+		break;
+	case 4:
+		drm_draw_blit32(dst, dst_pitch, src, src_pitch, height, width, scale, color);
+		break;
+	default:
+		WARN_ONCE(1, "Can't blit with pixel width %d\n", px_width);
+	}
+}
+
+static void drm_log_clear_line(struct drm_log_scanout *scanout, u32 line)
+{
+	struct drm_framebuffer *fb = scanout->buffer->fb;
+	unsigned long height = scanout->scaled_font_h;
+	struct iosys_map map;
+	struct drm_rect r = DRM_RECT_INIT(0, line * height, fb->width, height);
+
+	if (drm_client_buffer_vmap_local(scanout->buffer, &map))
+		return;
+	iosys_map_memset(&map, r.y1 * fb->pitches[0], 0, height * fb->pitches[0]);
+	drm_client_buffer_vunmap_local(scanout->buffer);
+	drm_client_buffer_flush(scanout->buffer, &r);
+}
+
+static void drm_log_draw_line(struct drm_log_scanout *scanout, const char *s,
+			      unsigned int len, unsigned int prefix_len)
+{
+	struct drm_framebuffer *fb = scanout->buffer->fb;
+	struct iosys_map map;
+	const struct font_desc *font = scanout->font;
+	size_t font_pitch = DIV_ROUND_UP(font->width, 8);
+	const u8 *src;
+	u32 px_width = fb->format->cpp[0];
+	struct drm_rect r = DRM_RECT_INIT(0, scanout->line * scanout->scaled_font_h,
+					  fb->width, (scanout->line + 1) * scanout->scaled_font_h);
+	u32 i;
+
+	if (drm_client_buffer_vmap_local(scanout->buffer, &map))
+		return;
+
+	iosys_map_incr(&map, r.y1 * fb->pitches[0]);
+	for (i = 0; i < len && i < scanout->columns; i++) {
+		u32 color = (i < prefix_len) ? scanout->prefix_color : scanout->front_color;
+		src = font_data_glyph_buf(font->data, font->width, font->height,
+					  (unsigned char)s[i]);
+		if (src)
+			drm_log_blit(&map, fb->pitches[0], src, font_pitch,
+				     scanout->scaled_font_h, scanout->scaled_font_w,
+				     px_width, color);
+		iosys_map_incr(&map, scanout->scaled_font_w * px_width);
+	}
+
+	scanout->line++;
+	if (scanout->line >= scanout->rows)
+		scanout->line = 0;
+	drm_client_buffer_vunmap_local(scanout->buffer);
+	drm_client_buffer_flush(scanout->buffer, &r);
+}
+
+static void drm_log_draw_new_line(struct drm_log_scanout *scanout,
+				  const char *s, unsigned int len, unsigned int prefix_len)
+{
+	if (scanout->line == 0) {
+		drm_log_clear_line(scanout, 0);
+		drm_log_clear_line(scanout, 1);
+		drm_log_clear_line(scanout, 2);
+	} else if (scanout->line + 2 < scanout->rows)
+		drm_log_clear_line(scanout, scanout->line + 2);
+
+	drm_log_draw_line(scanout, s, len, prefix_len);
+}
+
+/*
+ * Depends on print_time() in printk.c
+ * Timestamp is written with "[%5lu.%06lu]"
+ */
+#define TS_PREFIX_LEN 13
+
+static void drm_log_draw_kmsg_record(struct drm_log_scanout *scanout,
+				     const char *s, unsigned int len)
+{
+	u32 prefix_len = 0;
+
+	if (!len)
+		return;
+
+	if (len > TS_PREFIX_LEN && s[0] == '[' && s[6] == '.' && s[TS_PREFIX_LEN] == ']')
+		prefix_len = TS_PREFIX_LEN + 1;
+
+	/* do not print the ending \n character */
+	if (s[len - 1] == '\n')
+		len--;
+
+	while (len > scanout->columns) {
+		drm_log_draw_new_line(scanout, s, scanout->columns, prefix_len);
+		s += scanout->columns;
+		len -= scanout->columns;
+		prefix_len = 0;
+	}
+	if (len)
+		drm_log_draw_new_line(scanout, s, len, prefix_len);
+}
+
+static u32 drm_log_find_usable_format(struct drm_plane *plane)
+{
+	int i;
+
+	for (i = 0; i < plane->format_count; i++)
+		if (drm_draw_can_convert_from_xrgb8888(plane->format_types[i]))
+			return plane->format_types[i];
+	return DRM_FORMAT_INVALID;
+}
+
+static int drm_log_setup_modeset(struct drm_client_dev *client,
+				 struct drm_mode_set *mode_set,
+				 struct drm_log_scanout *scanout)
+{
+	struct drm_crtc *crtc = mode_set->crtc;
+	u32 width = mode_set->mode->hdisplay;
+	u32 height = mode_set->mode->vdisplay;
+	u32 format;
+
+	scanout->font = get_default_font(width, height, NULL, NULL);
+	if (!scanout->font)
+		return -ENOENT;
+
+	format = drm_log_find_usable_format(crtc->primary);
+	if (format == DRM_FORMAT_INVALID)
+		return -EINVAL;
+
+	scanout->buffer = drm_client_buffer_create_dumb(client, width, height, format);
+	if (IS_ERR(scanout->buffer)) {
+		drm_warn(client->dev, "drm_log can't create framebuffer %d %d %p4cc\n",
+			 width, height, &format);
+		return -ENOMEM;
+	}
+	mode_set->fb = scanout->buffer->fb;
+	scanout->scaled_font_h = scanout->font->height * scale;
+	scanout->scaled_font_w = scanout->font->width * scale;
+	scanout->rows = height / scanout->scaled_font_h;
+	scanout->columns = width / scanout->scaled_font_w;
+	if (!scanout->rows || !scanout->columns) {
+		drm_client_buffer_delete(scanout->buffer);
+		scanout->buffer = NULL;
+		mode_set->fb = NULL;
+		return -EINVAL;
+	}
+	scanout->front_color = drm_draw_color_from_xrgb8888(0xffffff, format);
+	scanout->prefix_color = drm_draw_color_from_xrgb8888(0x4e9a06, format);
+	return 0;
+}
+
+static int drm_log_count_modeset(struct drm_client_dev *client)
+{
+	struct drm_mode_set *mode_set;
+	int count = 0;
+
+	mutex_lock(&client->modeset_mutex);
+	drm_client_for_each_modeset(mode_set, client)
+		count++;
+	mutex_unlock(&client->modeset_mutex);
+	return count;
+}
+
+static void drm_log_init_client(struct drm_log *dlog)
+{
+	struct drm_client_dev *client = &dlog->client;
+	struct drm_mode_set *mode_set;
+	int i, max_modeset;
+	int n_modeset = 0;
+
+	dlog->probed = true;
+
+	if (drm_client_modeset_probe(client, 0, 0))
+		return;
+
+	max_modeset = drm_log_count_modeset(client);
+	if (!max_modeset)
+		return;
+
+	dlog->scanout = kzalloc_objs(*dlog->scanout, max_modeset);
+	if (!dlog->scanout)
+		return;
+
+	mutex_lock(&client->modeset_mutex);
+	drm_client_for_each_modeset(mode_set, client) {
+		if (!mode_set->mode)
+			continue;
+		if (drm_log_setup_modeset(client, mode_set, &dlog->scanout[n_modeset]))
+			continue;
+		n_modeset++;
+	}
+	mutex_unlock(&client->modeset_mutex);
+	if (n_modeset == 0)
+		goto err_nomodeset;
+
+	if (drm_client_modeset_commit(client))
+		goto err_failed_commit;
+
+	dlog->n_scanout = n_modeset;
+	return;
+
+err_failed_commit:
+	for (i = 0; i < n_modeset; i++)
+		drm_client_buffer_delete(dlog->scanout[i].buffer);
+
+err_nomodeset:
+	kfree(dlog->scanout);
+	dlog->scanout = NULL;
+}
+
+static void drm_log_free_scanout(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+	int i;
+
+	if (dlog->n_scanout) {
+		for (i = 0; i < dlog->n_scanout; i++)
+			drm_client_buffer_delete(dlog->scanout[i].buffer);
+		dlog->n_scanout = 0;
+		kfree(dlog->scanout);
+		dlog->scanout = NULL;
+	}
+}
+
+static void drm_log_client_free(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+	struct drm_device *dev = client->dev;
+
+	kfree(dlog);
+
+	drm_dbg(dev, "Unregistered with drm log\n");
+}
+
+static void drm_log_client_unregister(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+
+	unregister_console(&dlog->con);
+
+	mutex_lock(&dlog->lock);
+	drm_log_free_scanout(client);
+	mutex_unlock(&dlog->lock);
+	drm_client_release(client);
+}
+
+static int drm_log_client_restore(struct drm_client_dev *client, bool force)
+{
+	int ret;
+
+	if (force)
+		ret = drm_client_modeset_commit_locked(client);
+	else
+		ret = drm_client_modeset_commit(client);
+
+	return ret;
+}
+
+static int drm_log_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+
+	mutex_lock(&dlog->lock);
+	drm_log_free_scanout(client);
+	dlog->probed = false;
+	mutex_unlock(&dlog->lock);
+	return 0;
+}
+
+static int drm_log_client_suspend(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+
+	console_suspend(&dlog->con);
+
+	return 0;
+}
+
+static int drm_log_client_resume(struct drm_client_dev *client)
+{
+	struct drm_log *dlog = client_to_drm_log(client);
+
+	console_resume(&dlog->con);
+
+	return 0;
+}
+
+static const struct drm_client_funcs drm_log_client_funcs = {
+	.owner		= THIS_MODULE,
+	.free		= drm_log_client_free,
+	.unregister	= drm_log_client_unregister,
+	.restore	= drm_log_client_restore,
+	.hotplug	= drm_log_client_hotplug,
+	.suspend	= drm_log_client_suspend,
+	.resume		= drm_log_client_resume,
+};
+
+static void drm_log_write_thread(struct console *con, struct nbcon_write_context *wctxt)
+{
+	struct drm_log *dlog = console_to_drm_log(con);
+	int i;
+
+	if (!dlog->probed)
+		drm_log_init_client(dlog);
+
+	/* Check that we are still the master before drawing */
+	if (drm_master_internal_acquire(dlog->client.dev)) {
+		drm_master_internal_release(dlog->client.dev);
+
+		for (i = 0; i < dlog->n_scanout; i++)
+			drm_log_draw_kmsg_record(&dlog->scanout[i], wctxt->outbuf, wctxt->len);
+	}
+}
+
+static void drm_log_lock(struct console *con, unsigned long *flags)
+{
+	struct drm_log *dlog = console_to_drm_log(con);
+
+	mutex_lock(&dlog->lock);
+	migrate_disable();
+}
+
+static void drm_log_unlock(struct console *con, unsigned long flags)
+{
+	struct drm_log *dlog = console_to_drm_log(con);
+
+	migrate_enable();
+	mutex_unlock(&dlog->lock);
+}
+
+static void drm_log_register_console(struct console *con)
+{
+	strscpy(con->name, "drm_log");
+	con->write_thread = drm_log_write_thread;
+	con->device_lock = drm_log_lock;
+	con->device_unlock = drm_log_unlock;
+	con->flags = CON_PRINTBUFFER | CON_NBCON;
+	con->index = -1;
+
+	register_console(con);
+}
+
+/**
+ * drm_log_register() - Register a drm device to drm_log
+ * @dev: the drm device to register.
+ */
+void drm_log_register(struct drm_device *dev)
+{
+	struct drm_log *new;
+
+	if (!scale)
+		scale = 1;
+
+	new = kzalloc_obj(*new);
+	if (!new)
+		goto err_warn;
+
+	mutex_init(&new->lock);
+	if (drm_client_init(dev, &new->client, "drm_log", &drm_log_client_funcs))
+		goto err_free;
+
+	drm_client_register(&new->client);
+
+	drm_log_register_console(&new->con);
+
+	drm_dbg(dev, "Registered with drm log as %s\n", new->con.name);
+	return;
+
+err_free:
+	kfree(new);
+err_warn:
+	drm_warn(dev, "Failed to register with drm log\n");
+}