drm/panic: Add drm_panic_is_enabled()

It allows to check if the drm device supports drm_panic.
Prepare the work to have better integration with fbcon and vtconsole.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20240717090102.968152-2-jfalempe@redhat.com

drivers/gpu/drm/drm_crtc_internal.h

@@ -317,4 +317,11 @@ drm_edid_load_firmware(struct drm_connector *connector)
 }
 #endif
 
+/* drm_panic.c */
+#ifdef CONFIG_DRM_PANIC
+bool drm_panic_is_enabled(struct drm_device *dev);
+#else
+bool drm_panic_is_enabled(struct drm_device *dev) {return false; }
+#endif
+
 #endif /* __DRM_CRTC_INTERNAL_H__ */

drivers/gpu/drm/drm_panic.c

@@ -703,6 +703,26 @@ static void debugfs_register_plane(struct drm_plane *plane, int index)
 static void debugfs_register_plane(struct drm_plane *plane, int index) {}
 #endif /* CONFIG_DRM_PANIC_DEBUG */
 
+/**
+ * drm_panic_is_enabled
+ * @dev: the drm device that may supports drm_panic
+ *
+ * returns true if the drm device supports drm_panic
+ */
+bool drm_panic_is_enabled(struct drm_device *dev)
+{
+	struct drm_plane *plane;
+
+	if (!dev->mode_config.num_total_plane)
+		return false;
+
+	drm_for_each_plane(plane, dev)
+		if (plane->helper_private && plane->helper_private->get_scanout_buffer)
+			return true;
+	return false;
+}
+EXPORT_SYMBOL(drm_panic_is_enabled);
+
 /**
  * drm_panic_register() - Initialize DRM panic for a device
  * @dev: the drm device on which the panic screen will be displayed.