Re: [PATCH 09/12] drm/panic: Display panic screen via per-plane callback

On 18/08/2026 14:28, Thomas Zimmermann wrote:
> Add display_panic_screen to struct drm_plane_funcs. If set on a plane,
> register a panic handler for the plane from the DRM core's panic
> handling. Invoke this helper from the core to display a panic screen.
> 
> The new callback replaces get_scanout_buffer as signal for panic
> support in a plane. Using get_scanout_buffer is now merely a detail
> of the implementation. This will also free struct drm_scanout_buffer
> for use cases besides panic handling.
> 
> With display_panic_screen in place, rename draw_panic_plane() to
> drm_plane_helper_display_panic_screen() and make it available to DRM
> drivers via drm_panic_helper.h. Do not change the implementation or
> functionality of this code. drm_plane_helper_display_panic_screen()
> still supports kernel messages, user messages and QR codes on various
> color formats.
> 
> Then update all drivers that implement panic support. Provide the
> initializer macro DRM_PANIC_PLANE_FUNCS that sets display_panic_screen
> to drm_plane_helper_display_panic_screen(). If panic handling has
> been disabled, it instead clears the callback. There's again no change
> in functionality.
> 
> This logically splits panic handling into a set of entry points in the
> DRM code and a set of helper functions provided by drivers. The core
> invokes the driver's helper via callback, while the driver can tailor
> the implementation to its needs. Panic handling now works like most
> other interfaces in the DRM framework.
> 
> Locking and state-handling happens in the DRM core or helpers. Drivers
> that receive a call to display_panic_screen can assume that no concurrent
> modeset takes place on the plane or its CRTC.
> 
> Also update the documentation. Move information about locking and state
> guarantees from drm_panic_trylock() to display_panic_screen, where
> drivers authors can find it easily. Move information about the features
> of the current implementation to drm_panic_helper_display_panic_screen().
> 

Thanks, it looks good to me.

Reviewed-by: Jocelyn Falempe <[email protected]>

> Signed-off-by: Thomas Zimmermann <[email protected]>
> ---
>   MAINTAINERS                                   |  3 +-
>   .../amd/display/amdgpu_dm/amdgpu_dm_plane.c   |  2 +
>   drivers/gpu/drm/ast/ast_mode.c                |  2 +
>   drivers/gpu/drm/drm_panic.c                   | 78 ++++++++++---------
>   drivers/gpu/drm/hyperv/hyperv_drm_modeset.c   |  2 +
>   drivers/gpu/drm/i915/display/i9xx_plane.c     |  3 +
>   .../drm/i915/display/skl_universal_plane.c    |  4 +
>   drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c       |  2 +
>   drivers/gpu/drm/mgag200/mgag200_drv.h         |  4 +-
>   drivers/gpu/drm/nouveau/dispnv50/wndw.c       |  2 +
>   .../gpu/drm/renesas/rcar-du/rcar_du_plane.c   |  2 +
>   .../drm/renesas/shmobile/shmob_drm_plane.c    |  2 +
>   drivers/gpu/drm/sysfb/drm_sysfb_helper.h      |  4 +-
>   drivers/gpu/drm/sysfb/vesadrm.c               |  1 +
>   drivers/gpu/drm/tidss/tidss_plane.c           |  2 +
>   drivers/gpu/drm/tiny/bochs.c                  |  4 +-
>   drivers/gpu/drm/virtio/virtgpu_plane.c        |  2 +
>   include/drm/drm_mode_config.h                 |  4 +-
>   include/drm/drm_modeset_helper_vtables.h      | 11 ++-
>   include/drm/drm_panic.h                       | 49 +++---------
>   include/drm/drm_panic_helper.h                | 27 +++++++
>   include/drm/drm_plane.h                       | 57 ++++++++++++++
>   22 files changed, 180 insertions(+), 87 deletions(-)
>   create mode 100644 include/drm/drm_panic_helper.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 928b3ba23a76..472c5c48729d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -9020,7 +9020,8 @@ F:	drivers/gpu/drm/drm_draw.c
>   F:	drivers/gpu/drm/drm_draw_internal.h
>   F:	drivers/gpu/drm/drm_panic*.c
>   F:	drivers/gpu/drm/tests/drm_panic_test.c
> -F:	include/drm/drm_panic*
> +F:	include/drm/drm_panic.h
> +F:	include/drm/drm_panic_helper.h
>   
>   DRM PANIC QR CODE
>   M:	Jocelyn Falempe <[email protected]>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> index 824ef3ce5de0..eadc22a255bb 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> @@ -28,6 +28,7 @@
>   #include <drm/drm_blend.h>
>   #include "drm/drm_framebuffer.h"
>   #include <drm/drm_gem_atomic_helper.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_plane_helper.h>
>   #include <drm/drm_gem_framebuffer_helper.h>
>   #include <drm/drm_fourcc.h>
> @@ -2177,6 +2178,7 @@ static const struct drm_plane_funcs dm_plane_funcs = {
>   	.atomic_set_property = dm_atomic_plane_set_property,
>   	.atomic_get_property = dm_atomic_plane_get_property,
>   #endif
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   int amdgpu_dm_plane_init(struct amdgpu_display_manager *dm,
> diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
> index d5ed8c5c7925..ceebf9421100 100644
> --- a/drivers/gpu/drm/ast/ast_mode.c
> +++ b/drivers/gpu/drm/ast/ast_mode.c
> @@ -43,6 +43,7 @@
>   #include <drm/drm_gem_shmem_helper.h>
>   #include <drm/drm_managed.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_probe_helper.h>
>   
> @@ -652,6 +653,7 @@ static const struct drm_plane_funcs ast_primary_plane_funcs = {
>   	.disable_plane = drm_atomic_helper_disable_plane,
>   	.destroy = drm_plane_cleanup,
>   	DRM_GEM_SHADOW_PLANE_FUNCS,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static int ast_primary_plane_init(struct ast_device *ast)
> diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
> index 2263a11efdf6..2ecb4d1f6d47 100644
> --- a/drivers/gpu/drm/drm_panic.c
> +++ b/drivers/gpu/drm/drm_panic.c
> @@ -28,6 +28,7 @@
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_modeset_helper_vtables.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_plane.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_rect.h>
> @@ -42,32 +43,18 @@ MODULE_LICENSE("GPL");
>   /**
>    * DOC: overview
>    *
> - * To enable DRM panic for a driver, the primary plane must implement a
> - * &drm_plane_helper_funcs.get_scanout_buffer helper function. It is then
> - * automatically registered to the drm panic handler.
> - * When a panic occurs, the &drm_plane_helper_funcs.get_scanout_buffer will be
> - * called, and the driver can provide a framebuffer so the panic handler can
> - * draw the panic screen on it. Currently only linear buffer and a few color
> - * formats are supported.
> - * Optionally the driver can also provide a &drm_plane_helper_funcs.panic_flush
> - * callback, that will be called after that, to send additional commands to the
> - * hardware to make the scanout buffer visible.
> - */
> -
> -/*
> - * This module displays a user friendly message on screen when a kernel panic
> - * occurs. This is conflicting with fbcon, so you can only enable it when fbcon
> - * is disabled.
> - * It's intended for end-user, so have minimal technical/debug information.
> + * This module displays a user friendly message on screen when a kernel
> + * panic occurs. This is conflicting with fbcon, so you can only enable
> + * it when fbcon is disabled. It's intended for end users and therefore
> + * have minimal technical/debug information.
>    *
> - * Implementation details:
> + * To enable DRM panic for a driver, the at least one primary plane must
> + * implement struct &drm_plane_funcs.display_panic_screen. The plane is
> + * then automatically registered to the drm panic handler.
>    *
> - * It is a panic handler, so it can't take lock, allocate memory, run tasks/irq,
> - * or attempt to sleep. It's a best effort, and it may not be able to display
> - * the message in all situations (like if the panic occurs in the middle of a
> - * modesetting).
> - * It will display only one static frame, so performance optimizations are low
> - * priority as the machine is already in an unusable state.
> + * When a panic occurs, the DRM panic handler calls struct
> + * &drm_plane_funcs.display_panic_screen. See
> + * drm_plane_helper_display_panic_screen() for a generic implementation.
>    */
>   
>   struct drm_panic_line {
> @@ -821,12 +808,6 @@ static void drm_panic_qr_init(void) {};
>   static void drm_panic_qr_exit(void) {};
>   #endif
>   
> -enum drm_panic_type {
> -	DRM_PANIC_TYPE_KMSG,
> -	DRM_PANIC_TYPE_USER,
> -	DRM_PANIC_TYPE_QR,
> -};
> -
>   static enum drm_panic_type drm_panic_type = -1;
>   
>   static const char *drm_panic_type_map[] = {
> @@ -940,9 +921,29 @@ static void drm_panic_clear_description(void)
>   	desc_line->txt = NULL;
>   }
>   
> -static void draw_panic_plane(struct drm_plane *plane, const char *description,
> -			     enum drm_panic_type panic_type, u32 fg_color, u32 bg_color,
> -			     unsigned int qr_version)
> +/**
> + * drm_plane_helper_display_panic_screen - Displays a panic screen according to the given settings
> + * @plane: the DRM plane to display to
> + * @description: error message to display
> + * @panic_type: type of panic screen
> + * @fg_color: text foreground color
> + * @bg_color: text background color
> + * @qr_version: version of the QR code, if any
> + *
> + * This helper display a panic screen on common primary planes. The panic
> + * screen can either display a kernel message, a user message or a QR code.
> + *
> + * The helper uses struct drm_plane_helper_funcs.get_scanout_buffer, where
> + * the plane can provide a scanout buffer that the panic handler can draw to.
> + * Currently only linear buffer and a few color formats are supported.
> + *
> + * Optionally the plane can also provide a &drm_plane_helper_funcs.panic_flush
> + * callback, which the DRM panic handler calls after drawing to send additional
> + * commands to the hardware to make the scanout buffer visible.
> + */
> +void drm_plane_helper_display_panic_screen(struct drm_plane *plane, const char *description,
> +					   enum drm_panic_type panic_type,
> +					   u32 fg_color, u32 bg_color, unsigned int qr_version)
>   {
>   	struct drm_scanout_buffer sb = { };
>   	int ret;
> @@ -970,6 +971,7 @@ static void draw_panic_plane(struct drm_plane *plane, const char *description,
>   
>   	drm_panic_clear_description();
>   }
> +EXPORT_SYMBOL(drm_plane_helper_display_panic_screen);
>   
>   static void drm_panic_display_panic_screen(struct drm_plane *plane, const char *description)
>   {
> @@ -992,8 +994,8 @@ static void drm_panic_display_panic_screen(struct drm_plane *plane, const char *
>   	unsigned long flags;
>   
>   	if (drm_panic_trylock(dev, flags)) {
> -		draw_panic_plane(plane, description, drm_panic_type,
> -				 fg_color, bg_color, qr_version);
> +		plane->funcs->display_panic_screen(plane, description, drm_panic_type,
> +						   fg_color, bg_color, qr_version);
>   		drm_panic_unlock(dev, flags);
>   	}
>   }
> @@ -1064,7 +1066,7 @@ bool drm_panic_is_enabled(struct drm_device *dev)
>   		return false;
>   
>   	drm_for_each_plane(plane, dev)
> -		if (plane->helper_private && plane->helper_private->get_scanout_buffer)
> +		if (plane->funcs && plane->funcs->display_panic_screen)
>   			return true;
>   	return false;
>   }
> @@ -1083,7 +1085,7 @@ void drm_panic_register(struct drm_device *dev)
>   		return;
>   
>   	drm_for_each_plane(plane, dev) {
> -		if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
> +		if (!plane->funcs || !plane->funcs->display_panic_screen)
>   			continue;
>   		plane->kmsg_panic.dump = drm_panic;
>   		plane->kmsg_panic.max_reason = KMSG_DUMP_PANIC;
> @@ -1110,7 +1112,7 @@ void drm_panic_unregister(struct drm_device *dev)
>   		return;
>   
>   	drm_for_each_plane(plane, dev) {
> -		if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
> +		if (!plane->funcs || !plane->funcs->display_panic_screen)
>   			continue;
>   		kmsg_dump_unregister(&plane->kmsg_panic);
>   	}
> diff --git a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> index 1855749c1e41..3bf228ef97ff 100644
> --- a/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> +++ b/drivers/gpu/drm/hyperv/hyperv_drm_modeset.c
> @@ -18,6 +18,7 @@
>   #include <drm/drm_gem_shmem_helper.h>
>   #include <drm/drm_probe_helper.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_plane.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_vblank.h>
> @@ -237,6 +238,7 @@ static const struct drm_plane_funcs hv_drm_plane_funcs = {
>   	.disable_plane		= drm_atomic_helper_disable_plane,
>   	.destroy		= drm_plane_cleanup,
>   	DRM_GEM_SHADOW_PLANE_FUNCS,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const struct drm_encoder_funcs hv_drm_simple_encoder_funcs_cleanup = {
> diff --git a/drivers/gpu/drm/i915/display/i9xx_plane.c b/drivers/gpu/drm/i915/display/i9xx_plane.c
> index df6da1c6a359..0902b17d0269 100644
> --- a/drivers/gpu/drm/i915/display/i9xx_plane.c
> +++ b/drivers/gpu/drm/i915/display/i9xx_plane.c
> @@ -8,6 +8,7 @@
>   #include <drm/drm_atomic_helper.h>
>   #include <drm/drm_blend.h>
>   #include <drm/drm_fourcc.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   
>   #include "i9xx_plane.h"
> @@ -887,6 +888,7 @@ static const struct drm_plane_funcs i965_plane_funcs = {
>   	.atomic_destroy_state = intel_plane_destroy_state,
>   	.format_mod_supported = i965_plane_format_mod_supported,
>   	.format_mod_supported_async = intel_plane_format_mod_supported_async,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const struct drm_plane_funcs i8xx_plane_funcs = {
> @@ -897,6 +899,7 @@ static const struct drm_plane_funcs i8xx_plane_funcs = {
>   	.atomic_destroy_state = intel_plane_destroy_state,
>   	.format_mod_supported = i8xx_plane_format_mod_supported,
>   	.format_mod_supported_async = intel_plane_format_mod_supported_async,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static void i9xx_disable_tiling(struct intel_plane *plane)
> diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> index 07a683293352..45e8379d93d4 100644
> --- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> +++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> @@ -7,6 +7,7 @@
>   #include <drm/drm_blend.h>
>   #include <drm/drm_damage_helper.h>
>   #include <drm/drm_fourcc.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   #include <drm/intel/step.h>
>   
> @@ -2707,6 +2708,7 @@ static const struct drm_plane_funcs skl_plane_funcs = {
>   	.atomic_destroy_state = intel_plane_destroy_state,
>   	.format_mod_supported = skl_plane_format_mod_supported,
>   	.format_mod_supported_async = intel_plane_format_mod_supported_async,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const struct drm_plane_funcs icl_plane_funcs = {
> @@ -2717,6 +2719,7 @@ static const struct drm_plane_funcs icl_plane_funcs = {
>   	.atomic_destroy_state = intel_plane_destroy_state,
>   	.format_mod_supported = icl_plane_format_mod_supported,
>   	.format_mod_supported_async = intel_plane_format_mod_supported_async,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const struct drm_plane_funcs tgl_plane_funcs = {
> @@ -2727,6 +2730,7 @@ static const struct drm_plane_funcs tgl_plane_funcs = {
>   	.atomic_destroy_state = intel_plane_destroy_state,
>   	.format_mod_supported = tgl_plane_format_mod_supported,
>   	.format_mod_supported_async = intel_plane_format_mod_supported_async,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static void
> diff --git a/drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c b/drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c
> index c7ec09e557c1..377db7cea726 100644
> --- a/drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c
> +++ b/drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c
> @@ -14,6 +14,7 @@
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_gem_dma_helper.h>
>   #include <drm/drm_managed.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   
>   #include <video/imx-ipu-v3.h>
> @@ -362,6 +363,7 @@ static const struct drm_plane_funcs ipu_plane_funcs = {
>   	.atomic_duplicate_state	= ipu_plane_duplicate_state,
>   	.atomic_destroy_state	= ipu_plane_destroy_state,
>   	.format_mod_supported = ipu_plane_format_mod_supported,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static int ipu_plane_atomic_check(struct drm_plane *plane,
> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
> index 3732c62351bb..d3995ce876f4 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_drv.h
> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
> @@ -17,6 +17,7 @@
>   #include <drm/drm_encoder.h>
>   #include <drm/drm_gem.h>
>   #include <drm/drm_gem_shmem_helper.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_plane.h>
>   
>   #include "mgag200_reg.h"
> @@ -386,7 +387,8 @@ int mgag200_primary_plane_helper_get_scanout_buffer(struct drm_plane *plane,
>   	.update_plane = drm_atomic_helper_update_plane, \
>   	.disable_plane = drm_atomic_helper_disable_plane, \
>   	.destroy = drm_plane_cleanup, \
> -	DRM_GEM_SHADOW_PLANE_FUNCS
> +	DRM_GEM_SHADOW_PLANE_FUNCS, \
> +	DRM_PANIC_PLANE_FUNCS
>   
>   void mgag200_crtc_fill_gamma(struct mga_device *mdev, const struct drm_format_info *format);
>   void mgag200_crtc_load_gamma(struct mga_device *mdev,
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> index 15a322422f4e..fc29a291e96f 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
> @@ -39,6 +39,7 @@
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/ttm/ttm_bo.h>
>   
>   #include "nouveau_bo.h"
> @@ -841,6 +842,7 @@ nv50_wndw = {
>   	.atomic_duplicate_state = nv50_wndw_atomic_duplicate_state,
>   	.atomic_destroy_state = nv50_wndw_atomic_destroy_state,
>   	.format_mod_supported = nv50_plane_format_mod_supported,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const u64 nv50_cursor_format_modifiers[] = {
> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_du_plane.c b/drivers/gpu/drm/renesas/rcar-du/rcar_du_plane.c
> index 8870766b9e54..f4b0e5b70c7d 100644
> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_du_plane.c
> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_du_plane.c
> @@ -16,6 +16,7 @@
>   #include <drm/drm_fourcc.h>
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_gem_dma_helper.h>
> +#include <drm/drm_panic_helper.h>
>   
>   #include "rcar_du_drv.h"
>   #include "rcar_du_group.h"
> @@ -773,6 +774,7 @@ static const struct drm_plane_funcs rcar_du_plane_funcs = {
>   	.atomic_destroy_state = rcar_du_plane_atomic_destroy_state,
>   	.atomic_set_property = rcar_du_plane_atomic_set_property,
>   	.atomic_get_property = rcar_du_plane_atomic_get_property,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const uint32_t formats[] = {
> diff --git a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c b/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> index 148de34af785..907f85462fa0 100644
> --- a/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> +++ b/drivers/gpu/drm/renesas/shmobile/shmob_drm_plane.c
> @@ -14,6 +14,7 @@
>   #include <drm/drm_fourcc.h>
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_gem_dma_helper.h>
> +#include <drm/drm_panic_helper.h>
>   
>   #include "shmob_drm_drv.h"
>   #include "shmob_drm_kms.h"
> @@ -286,6 +287,7 @@ static const struct drm_plane_funcs shmob_drm_plane_funcs = {
>   	.reset = shmob_drm_plane_reset,
>   	.atomic_duplicate_state = shmob_drm_plane_atomic_duplicate_state,
>   	.atomic_destroy_state = shmob_drm_plane_atomic_destroy_state,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static const uint32_t formats[] = {
> diff --git a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
> index 547f2327af5e..232be339659e 100644
> --- a/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
> +++ b/drivers/gpu/drm/sysfb/drm_sysfb_helper.h
> @@ -12,6 +12,7 @@
>   #include <drm/drm_device.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_modes.h>
> +#include <drm/drm_panic_helper.h>
>   
>   struct drm_format_info;
>   struct drm_scanout_buffer;
> @@ -144,7 +145,8 @@ void drm_sysfb_plane_atomic_destroy_state(struct drm_plane *plane,
>   	.update_plane = drm_atomic_helper_update_plane, \
>   	.disable_plane = drm_atomic_helper_disable_plane, \
>   	.atomic_duplicate_state = drm_sysfb_plane_atomic_duplicate_state, \
> -	.atomic_destroy_state = drm_sysfb_plane_atomic_destroy_state
> +	.atomic_destroy_state = drm_sysfb_plane_atomic_destroy_state, \
> +	DRM_PANIC_PLANE_FUNCS
>   
>   /*
>    * CRTC
> diff --git a/drivers/gpu/drm/sysfb/vesadrm.c b/drivers/gpu/drm/sysfb/vesadrm.c
> index 6a67b2d2e451..14d2e6ab88aa 100644
> --- a/drivers/gpu/drm/sysfb/vesadrm.c
> +++ b/drivers/gpu/drm/sysfb/vesadrm.c
> @@ -24,6 +24,7 @@
>   #include <drm/drm_managed.h>
>   #include <drm/drm_modeset_helper.h>
>   #include <drm/drm_modeset_helper_vtables.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_probe_helper.h>
>   
> diff --git a/drivers/gpu/drm/tidss/tidss_plane.c b/drivers/gpu/drm/tidss/tidss_plane.c
> index 6d82976c2db1..b0d5d6959b88 100644
> --- a/drivers/gpu/drm/tidss/tidss_plane.c
> +++ b/drivers/gpu/drm/tidss/tidss_plane.c
> @@ -12,6 +12,7 @@
>   #include <drm/drm_fourcc.h>
>   #include <drm/drm_framebuffer.h>
>   #include <drm/drm_gem_atomic_helper.h>
> +#include <drm/drm_panic_helper.h>
>   
>   #include "tidss_crtc.h"
>   #include "tidss_dispc.h"
> @@ -182,6 +183,7 @@ static const struct drm_plane_funcs tidss_plane_funcs = {
>   	.atomic_create_state = drm_atomic_helper_plane_create_state,
>   	.atomic_duplicate_state = drm_atomic_helper_plane_duplicate_state,
>   	.atomic_destroy_state = drm_atomic_helper_plane_destroy_state,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   struct tidss_plane *tidss_plane_create(struct tidss_device *tidss,
> diff --git a/drivers/gpu/drm/tiny/bochs.c b/drivers/gpu/drm/tiny/bochs.c
> index e2d957e51505..076d19b26511 100644
> --- a/drivers/gpu/drm/tiny/bochs.c
> +++ b/drivers/gpu/drm/tiny/bochs.c
> @@ -20,6 +20,7 @@
>   #include <drm/drm_managed.h>
>   #include <drm/drm_module.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_plane_helper.h>
>   #include <drm/drm_print.h>
>   #include <drm/drm_probe_helper.h>
> @@ -501,7 +502,8 @@ static const struct drm_plane_funcs bochs_primary_plane_funcs = {
>   	.update_plane = drm_atomic_helper_update_plane,
>   	.disable_plane = drm_atomic_helper_disable_plane,
>   	.destroy = drm_plane_cleanup,
> -	DRM_GEM_SHADOW_PLANE_FUNCS
> +	DRM_GEM_SHADOW_PLANE_FUNCS,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static void bochs_crtc_helper_mode_set_nofb(struct drm_crtc *crtc)
> diff --git a/drivers/gpu/drm/virtio/virtgpu_plane.c b/drivers/gpu/drm/virtio/virtgpu_plane.c
> index 1d1b27ece62a..108b5b93f130 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_plane.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_plane.c
> @@ -30,6 +30,7 @@
>   #include <linux/virtio_dma_buf.h>
>   #include <drm/drm_managed.h>
>   #include <drm/drm_panic.h>
> +#include <drm/drm_panic_helper.h>
>   #include <drm/drm_print.h>
>   
>   #include "virtgpu_drv.h"
> @@ -94,6 +95,7 @@ static const struct drm_plane_funcs virtio_gpu_plane_funcs = {
>   	.reset			= drm_atomic_helper_plane_reset,
>   	.atomic_duplicate_state = virtio_gpu_plane_duplicate_state,
>   	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
> +	DRM_PANIC_PLANE_FUNCS,
>   };
>   
>   static int virtio_gpu_plane_atomic_check(struct drm_plane *plane,
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index d8f5b7e9673e..084517beb924 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -495,8 +495,8 @@ struct drm_mode_config {
>   	 *
>   	 * Raw spinlock used to protect critical sections of code that access
>   	 * the display hardware or modeset software state, which the panic
> -	 * printing code must be protected against. See drm_panic_trylock(),
> -	 * drm_panic_lock() and drm_panic_unlock().
> +	 * printing code must be protected against. See the documentation on
> +	 * DRM panic handling for more information.
>   	 */
>   	struct raw_spinlock panic_lock;
>   
> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
> index ca6268945c28..614bdee0c1ed 100644
> --- a/include/drm/drm_modeset_helper_vtables.h
> +++ b/include/drm/drm_modeset_helper_vtables.h
> @@ -1442,17 +1442,20 @@ struct drm_plane_helper_funcs {
>   	/**
>   	 * @get_scanout_buffer:
>   	 *
> -	 * Get the current scanout buffer, to display a message with drm_panic.
> +	 * Get the current scanout buffer to display a message with drm_panic.
>   	 * The driver should do the minimum changes to provide a buffer,
>   	 * that can be used to display the panic screen. Currently only linear
>   	 * buffers are supported. Non-linear buffer support is on the TODO list.
>   	 * The device &dev.mode_config.panic_lock is taken before calling this
>   	 * function, so you can safely access the &plane.state
>   	 * It is called from a panic callback, and must follow its restrictions.
> -	 * Please look the documentation at drm_panic_trylock() for an in-depth
> +	 * Please look the documentation on DRM panic handling for an in-depth
>   	 * discussions of what's safe and what is not allowed.
> +	 *
>   	 * It's a best effort mode, so it's expected that in some complex cases
> -	 * the panic screen won't be displayed.
> +	 * the panic screen won't be displayed. Drivers must not make any
> +	 * assumptions about the actual state of the hardware.
> +	 *
>   	 * The returned &drm_scanout_buffer.map must be valid if no error code is
>   	 * returned.
>   	 *
> @@ -1472,7 +1475,7 @@ struct drm_plane_helper_funcs {
>   	 * It is only called if get_scanout_buffer() returned successfully, and
>   	 * the &dev.mode_config.panic_lock is held during the entire sequence.
>   	 * It is called from a panic callback, and must follow its restrictions.
> -	 * Please look the documentation at drm_panic_trylock() for an in-depth
> +	 * Please look the documentation on DRM panic handling for an in-depth
>   	 * discussions of what's safe and what is not allowed.
>   	 */
>   	void (*panic_flush)(struct drm_plane *plane);
> diff --git a/include/drm/drm_panic.h b/include/drm/drm_panic.h
> index ac0e46b73436..430df536de14 100644
> --- a/include/drm/drm_panic.h
> +++ b/include/drm/drm_panic.h
> @@ -15,6 +15,14 @@
>   #include <drm/drm_device.h>
>   #include <drm/drm_fourcc.h>
>   
> +struct page;
> +
> +enum drm_panic_type {
> +	DRM_PANIC_TYPE_KMSG,
> +	DRM_PANIC_TYPE_USER,
> +	DRM_PANIC_TYPE_QR,
> +};
> +
>   /**
>    * struct drm_scanout_buffer - DRM scanout buffer
>    *
> @@ -87,45 +95,8 @@ struct drm_scanout_buffer {
>    * @dev: struct drm_device
>    * @flags: unsigned long irq flags you need to pass to the unlock() counterpart
>    *
> - * This function must be called by any panic printing code. The panic printing
> - * attempt must be aborted if the trylock fails.
> - *
> - * Panic printing code can make the following assumptions while holding the
> - * panic lock:
> - *
> - * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe
> - *   to access.
> - *
> - * - Furthermore the panic printing code only registers in drm_dev_unregister()
> - *   and gets removed in drm_dev_unregister(). This allows the panic code to
> - *   safely access any state which is invariant in between these two function
> - *   calls, like the list of planes &drm_mode_config.plane_list or most of the
> - *   struct drm_plane structure.
> - *
> - * Specifically thanks to the protection around plane updates in
> - * drm_atomic_helper_swap_state() the following additional guarantees hold:
> - *
> - * - It is safe to deference the drm_plane.state pointer.
> - *
> - * - Anything in struct drm_plane_state or the driver's subclass thereof which
> - *   stays invariant after the atomic check code has finished is safe to access.
> - *   Specifically this includes the reference counted pointers to framebuffer
> - *   and buffer objects.
> - *
> - * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up
> - *   &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays
> - *   invariant between these two calls. This also means that for drivers using
> - *   dynamic buffer management the framebuffer is pinned, and therefer all
> - *   relevant datastructures can be accessed without taking any further locks
> - *   (which would be impossible in panic context anyway).
> - *
> - * - Importantly, software and hardware state set up by
> - *   &drm_plane_helper_funcs.begin_fb_access and
> - *   &drm_plane_helper_funcs.end_fb_access is not safe to access.
> - *
> - * Drivers must not make any assumptions about the actual state of the hardware,
> - * unless they explicitly protected these hardware access with drm_panic_lock()
> - * and drm_panic_unlock().
> + * The panic-printing code calls this function. The panic printing attempt must
> + * be aborted if the trylock fails.
>    *
>    * Return:
>    * %0 when failing to acquire the raw spinlock, nonzero on success.
> diff --git a/include/drm/drm_panic_helper.h b/include/drm/drm_panic_helper.h
> new file mode 100644
> index 000000000000..e296620bbe34
> --- /dev/null
> +++ b/include/drm/drm_panic_helper.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 or MIT */
> +
> +#ifndef __DRM_DRM_PANIC_HELPER_H_
> +#define __DRM_DRM_PANIC_HELPER_H_
> +
> +#include <linux/types.h>
> +
> +enum drm_panic_type;
> +
> +struct drm_plane;
> +
> +/* drm_panic_helper.c */
> +void drm_plane_helper_display_panic_screen(struct drm_plane *plane,
> +					   const char *description,
> +					   enum drm_panic_type panic_type,
> +					   u32 fg_color, u32 bg_color,
> +					   unsigned int qr_version);
> +
> +#if IS_ENABLED(CONFIG_DRM_PANIC)
> +#define DRM_PANIC_PLANE_FUNCS \
> +	.display_panic_screen = drm_plane_helper_display_panic_screen
> +#else
> +#define DRM_PANIC_PLANE_FUNCS \
> +	.display_panic_screen = NULL
> +#endif
> +
> +#endif
> diff --git a/include/drm/drm_plane.h b/include/drm/drm_plane.h
> index 2c5a5a70a71b..317af17bac26 100644
> --- a/include/drm/drm_plane.h
> +++ b/include/drm/drm_plane.h
> @@ -32,6 +32,8 @@
>   #include <drm/drm_modeset_lock.h>
>   #include <drm/drm_util.h>
>   
> +enum drm_panic_type;
> +
>   struct drm_crtc;
>   struct drm_plane_size_hint;
>   struct drm_printer;
> @@ -590,6 +592,61 @@ struct drm_plane_funcs {
>   	bool (*format_mod_supported_async)(struct drm_plane *plane,
>   					   u32 format, u64 modifier);
>   
> +	/**
> +	 * @display_panic_screen:
> +	 *
> +	 * DRM panic handling invokes this callback on panics.
> +	 *
> +	 * It is a panic handler, so it can't take locks, allocate memory, run tasks/irq,
> +	 * or attempt to sleep. It's a best effort, and it may not be able to display
> +	 * the message in all situations (like if the panic occurs in the middle of a
> +	 * modesetting).
> +	 *
> +	 * Panic-printing code must acquire the panic lock before interacting with the
> +	 * scanout buffer. Such helpers can make the following assumptions while holding
> +	 * the panic lock:
> +	 *
> +	 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe
> +	 *   to access.
> +	 *
> +	 * - Furthermore the panic printing code only registers in drm_dev_unregister()
> +	 *   and gets removed in drm_dev_unregister(). This allows the panic code to
> +	 *   safely access any state which is invariant in between these two function
> +	 *   calls, like the list of planes &drm_mode_config.plane_list or most of the
> +	 *   struct drm_plane structure.
> +	 *
> +	 * Specifically thanks to the protection around plane updates in
> +	 * drm_atomic_helper_swap_state() the following additional guarantees hold:
> +	 *
> +	 * - It is safe to deference the drm_plane.state pointer.
> +	 *
> +	 * - Anything in struct drm_plane_state or the driver's subclass thereof which
> +	 *   stays invariant after the atomic check code has finished is safe to access.
> +	 *   Specifically this includes the reference counted pointers to framebuffer
> +	 *   and buffer objects.
> +	 *
> +	 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up
> +	 *   &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays
> +	 *   invariant between these two calls. This also means that for drivers using
> +	 *   dynamic buffer management the framebuffer is pinned, and therefer all
> +	 *   relevant datastructures can be accessed without taking any further locks
> +	 *   (which would be impossible in panic context anyway).
> +	 *
> +	 * - Importantly, software and hardware state set up by
> +	 *   &drm_plane_helper_funcs.begin_fb_access and
> +	 *   &drm_plane_helper_funcs.end_fb_access is not safe to access.
> +	 *
> +	 * It will display only one static frame, so performance optimizations are
> +	 * low priority as the machine is already in an unusable state.
> +	 *
> +	 * This callback is optional. Planes without will not be considered
> +	 * for panic output.
> +	 */
> +	void (*display_panic_screen)(struct drm_plane *plane,
> +				     const char *description,
> +				     enum drm_panic_type panic_type,
> +				     u32 fg_color, u32 bg_color,
> +				     unsigned int qr_version);
>   };
>   
>   /**