drm/panic: Compile KUnit tests as module

Fix dependency of the panic-helper KUnit tests on CONFIG_DRM_KUNIT_TEST=y
and make them build as a module. Export the necessary interfaces from the
panic helpers iff the KUnit framework has been enabled.

Select DRM_PANIC_HELPER from DRM_KUNIT_TEST to meet the dependencies of
the panic-helper tests.

It is now possible to run the tests by modprobe-ing drm_panic_helper_test
at runtime.

v5:
- clear test description with drm_panic_helper_clear_description() (Sashiko)
v3:
- clean up after each test case (Sashiko)
v2:
- fix parameter order in decl of drm_panic_helper_draw_screen_qr()
  (Sashiko)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patch.msgid.link/20260911124540.279841-15-tzimmermann@suse.de

drivers/gpu/drm/Kconfig.debug

@@ -69,6 +69,7 @@ config DRM_KUNIT_TEST
 	select DRM_EXPORT_FOR_TESTS if m
 	select DRM_GEM_SHMEM_HELPER
 	select DRM_KUNIT_TEST_HELPERS
+	select DRM_PANIC_HELPER
 	select DRM_SYSFB_HELPER
 	select PRIME_NUMBERS
 	default KUNIT_ALL_TESTS

drivers/gpu/drm/drm_panic_helper.c

@@ -8,6 +8,8 @@
 #include <linux/utsname.h>
 #include <linux/zlib.h>
 
+#include <kunit/visibility.h>
+
 #include <drm/drm_fourcc.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_modeset_helper_vtables.h>
@@ -433,8 +435,8 @@ static void drm_panic_helper_logo_draw(struct drm_scanout_buffer *sb, struct drm
 				   fg_color);
 }
 
-static int drm_panic_helper_draw_screen_user(struct drm_scanout_buffer *sb,
-					     u32 fg_color, u32 bg_color)
+VISIBLE_IF_KUNIT int drm_panic_helper_draw_screen_user(struct drm_scanout_buffer *sb,
+						       u32 fg_color, u32 bg_color)
 {
 	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
 	struct drm_rect r_screen, r_logo, r_msg;
@@ -466,6 +468,7 @@ static int drm_panic_helper_draw_screen_user(struct drm_scanout_buffer *sb,
 
 	return 0;
 }
+EXPORT_SYMBOL_IF_KUNIT(drm_panic_helper_draw_screen_user);
 
 /*
  * Draw one line of kmsg, and handle wrapping if it won't fit in the screen width.
@@ -504,8 +507,8 @@ static int draw_line_with_wrap(struct drm_scanout_buffer *sb, const struct font_
  * Draw the kmsg buffer to the screen, starting from the youngest message at the bottom,
  * and going up until reaching the top of the screen.
  */
-static int drm_panic_helper_draw_screen_kmsg(struct drm_scanout_buffer *sb,
-					     u32 fg_color, u32 bg_color)
+VISIBLE_IF_KUNIT int drm_panic_helper_draw_screen_kmsg(struct drm_scanout_buffer *sb,
+						       u32 fg_color, u32 bg_color)
 {
 	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
 	struct drm_rect r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);
@@ -549,6 +552,7 @@ static int drm_panic_helper_draw_screen_kmsg(struct drm_scanout_buffer *sb,
 
 	return 0;
 }
+EXPORT_SYMBOL_IF_KUNIT(drm_panic_helper_draw_screen_kmsg);
 
 #if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
 /*
@@ -691,9 +695,9 @@ static int drm_panic_helper_get_qr_code(u8 **qr_image, unsigned int qr_version)
 /*
  * Draw the panic message at the center of the screen, with a QR Code
  */
-static int drm_panic_helper_draw_screen_qr_code(struct drm_scanout_buffer *sb,
-						u32 fg_color, u32 bg_color,
-						unsigned int qr_version)
+VISIBLE_IF_KUNIT int drm_panic_helper_draw_screen_qr_code(struct drm_scanout_buffer *sb,
+							  u32 fg_color, u32 bg_color,
+							  unsigned int qr_version)
 {
 	const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
 	struct drm_rect r_screen, r_logo, r_msg, r_qr, r_qr_canvas;
@@ -763,6 +767,7 @@ static int drm_panic_helper_draw_screen_qr_code(struct drm_scanout_buffer *sb,
 	drm_panic_helper_blit(sb, &r_qr, qr_image, qr_pitch, scale, fg_color);
 	return 0;
 }
+EXPORT_SYMBOL_IF_KUNIT(drm_panic_helper_draw_screen_qr_code);
 #else
 static void __init drm_panic_helper_qr_init(void) { };
 static void __exit drm_panic_helper_qr_exit(void) { };
@@ -815,7 +820,7 @@ static int draw_panic_helper_dispatch(struct drm_scanout_buffer *sb,
 	return ret;
 }
 
-static void drm_panic_helper_set_description(const char *description)
+VISIBLE_IF_KUNIT void drm_panic_helper_set_description(const char *description)
 {
 	u32 len;
 
@@ -830,14 +835,16 @@ static void drm_panic_helper_set_description(const char *description)
 		desc_line->len = len;
 	}
 }
+EXPORT_SYMBOL_IF_KUNIT(drm_panic_helper_set_description);
 
-static void drm_panic_helper_clear_description(void)
+VISIBLE_IF_KUNIT void drm_panic_helper_clear_description(void)
 {
 	struct drm_panic_line *desc_line = &panic_msg[panic_msg_lines - 1];
 
 	desc_line->len = 0;
 	desc_line->txt = NULL;
 }
+EXPORT_SYMBOL_IF_KUNIT(drm_panic_helper_clear_description);
 
 /**
  * drm_plane_helper_display_panic_screen - Displays a panic screen according to the given settings
@@ -910,7 +917,3 @@ void __exit drm_panic_helper_exit(void)
 {
 	drm_panic_helper_qr_exit();
 }
-
-#ifdef CONFIG_DRM_KUNIT_TEST
-#include "tests/drm_panic_helper_test.c"
-#endif

drivers/gpu/drm/tests/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_DRM_KUNIT_TEST) += \
 	drm_managed_test.o \
 	drm_mm_test.o \
 	drm_modes_test.o \
+	drm_panic_helper_test.o \
 	drm_plane_helper_test.o \
 	drm_probe_helper_test.o \
 	drm_rect_test.o \

drivers/gpu/drm/tests/drm_panic_helper_test.c

@@ -6,13 +6,17 @@
  * KUNIT tests for DRM panic helpers
  */
 
-#include <drm/drm_fourcc.h>
-#include <drm/drm_panic.h>
+#include <linux/highmem.h>
+#include <linux/units.h>
+#include <linux/vmalloc.h>
 
 #include <kunit/test.h>
 
-#include <linux/units.h>
-#include <linux/vmalloc.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_panic.h>
+#include <drm/drm_panic_helper.h>
+
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");
 
 static void drm_panic_check_color_byte(struct kunit *test, u8 b)
 {
@@ -86,6 +90,11 @@ static int drm_test_panic_init(struct kunit *test)
 	return 0;
 }
 
+static void drm_test_panic_exit(struct kunit *test)
+{
+	drm_panic_helper_clear_description();
+}
+
 /*
  * Test drawing the panic screen, using a memory mapped framebuffer
  * Set the whole buffer to 0xa5, and then check that all pixels have been
@@ -229,7 +238,11 @@ static struct kunit_case drm_panic_screen_user_test[] = {
 static struct kunit_suite drm_panic_helper_suite = {
 	.name = "drm_panic_helper",
 	.init = drm_test_panic_init,
+	.exit = drm_test_panic_exit,
 	.test_cases = drm_panic_screen_user_test,
 };
 
 kunit_test_suite(drm_panic_helper_suite);
+
+MODULE_DESCRIPTION("KUnit test suite for DRM panic handling");
+MODULE_LICENSE("GPL");

include/drm/drm_panic_helper.h

@@ -8,6 +8,7 @@
 enum drm_panic_type;
 
 struct drm_plane;
+struct drm_scanout_buffer;
 
 /* drm_panic_helper.c */
 int drm_plane_helper_display_panic_screen(struct drm_plane *plane,
@@ -15,6 +16,14 @@ int drm_plane_helper_display_panic_screen(struct drm_plane *plane,
 					  enum drm_panic_type panic_type,
 					  u32 fg_color, u32 bg_color,
 					  unsigned int qr_version);
+#if IS_ENABLED(CONFIG_KUNIT)
+int drm_panic_helper_draw_screen_user(struct drm_scanout_buffer *sb, u32 fg_color, u32 bg_color);
+int drm_panic_helper_draw_screen_kmsg(struct drm_scanout_buffer *sb, u32 fg_color, u32 bg_color);
+int drm_panic_helper_draw_screen_qr_code(struct drm_scanout_buffer *sb,
+					 u32 fg_color, u32 bg_color, unsigned int qr_version);
+void drm_panic_helper_set_description(const char *description);
+void drm_panic_helper_clear_description(void);
+#endif
 
 /* drm_panic_helper_qr.rs */
 size_t drm_panic_helper_qr_max_data_size(u8 version, size_t url_len);