drm/fb-helper: Introduce drm_fb_helper_unprepare()

Move the fb-helper clean-up code into drm_fb_helper_unprepare(). No
functional changes.

v2:
	* declare as static inline (kernel test robot)
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230125200415.14123-4-tzimmermann@suse.de

drivers/gpu/drm/drm_fb_helper.c

@@ -433,6 +433,18 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 }
 EXPORT_SYMBOL(drm_fb_helper_prepare);
 
+/**
+ * drm_fb_helper_unprepare - clean up a drm_fb_helper structure
+ * @fb_helper: driver-allocated fbdev helper structure to set up
+ *
+ * Cleans up the framebuffer helper. Inverse of drm_fb_helper_prepare().
+ */
+void drm_fb_helper_unprepare(struct drm_fb_helper *fb_helper)
+{
+	mutex_destroy(&fb_helper->lock);
+}
+EXPORT_SYMBOL(drm_fb_helper_unprepare);
+
 /**
  * drm_fb_helper_init - initialize a &struct drm_fb_helper
  * @dev: drm device
@@ -559,7 +571,7 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
 	}
 	mutex_unlock(&kernel_fb_helper_lock);
 
-	mutex_destroy(&fb_helper->lock);
+	drm_fb_helper_unprepare(fb_helper);
 
 	if (!fb_helper->client.funcs)
 		drm_client_release(&fb_helper->client);

include/drm/drm_fb_helper.h

@@ -230,6 +230,7 @@ drm_fb_helper_from_client(struct drm_client_dev *client)
 #ifdef CONFIG_DRM_FBDEV_EMULATION
 void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
 			   const struct drm_fb_helper_funcs *funcs);
+void drm_fb_helper_unprepare(struct drm_fb_helper *fb_helper);
 int drm_fb_helper_init(struct drm_device *dev, struct drm_fb_helper *helper);
 void drm_fb_helper_fini(struct drm_fb_helper *helper);
 int drm_fb_helper_blank(int blank, struct fb_info *info);
@@ -296,6 +297,10 @@ static inline void drm_fb_helper_prepare(struct drm_device *dev,
 {
 }
 
+static inline void drm_fb_helper_unprepare(struct drm_fb_helper *fb_helper)
+{
+}
+
 static inline int drm_fb_helper_init(struct drm_device *dev,
 		       struct drm_fb_helper *helper)
 {