1 files changed, 35 insertions, 6 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 1bdfb37377e3..a63566ba230b 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -76,6 +76,7 @@ MODULE_LICENSE("GPL");
 static int brightness_switch_enabled = 1;
 module_param(brightness_switch_enabled, bool, 0644);
 
+static int register_count = 0;
 static int acpi_video_bus_add(struct acpi_device *device);
 static int acpi_video_bus_remove(struct acpi_device *device, int type);
 static int acpi_video_resume(struct acpi_device *device);
@@ -2318,6 +2319,13 @@ static int __init intel_opregion_present(void)
 int acpi_video_register(void)
 {
         int result = 0;
+        if (register_count) {
+                /*
+                 * if the function of acpi_video_register is already called,
+                 * don't register the acpi_vide_bus again and return no error.
+                 */
+                return 0;
+        }
 
         acpi_video_dir = proc_mkdir(ACPI_VIDEO_CLASS, acpi_root_dir);
         if (!acpi_video_dir)
@@ -2329,10 +2337,35 @@ int acpi_video_register(void)
                 return -ENODEV;
         }
 
+        /*
+         * When the acpi_video_bus is loaded successfully, increase
+         * the counter reference.
+         */
+        register_count = 1;
+
         return 0;
 }
 EXPORT_SYMBOL(acpi_video_register);
 
+void acpi_video_unregister(void)
+{
+        if (!register_count) {
+                /*
+                 * If the acpi video bus is already unloaded, don't
+                 * unload it again and return directly.
+                 */
+                return;
+        }
+        acpi_bus_unregister_driver(&acpi_video_bus);
+
+        remove_proc_entry(ACPI_VIDEO_CLASS, acpi_root_dir);
+
+        register_count = 0;
+
+        return;
+}
+EXPORT_SYMBOL(acpi_video_unregister);
+
 /*
  * This is kind of nasty. Hardware using Intel chipsets may require
  * the video opregion code to be run first in order to initialise
@@ -2350,16 +2383,12 @@ static int __init acpi_video_init(void)
         return acpi_video_register();
 }
 
-void acpi_video_exit(void)
+static void __exit acpi_video_exit(void)
 {
-
-        acpi_bus_unregister_driver(&acpi_video_bus);
-
-        remove_proc_entry(ACPI_VIDEO_CLASS, acpi_root_dir);
+        acpi_video_unregister();
 
         return;
 }
-EXPORT_SYMBOL(acpi_video_exit);
 
 module_init(acpi_video_init);
 module_exit(acpi_video_exit);