ACPI: Add the reference count to avoid unloading ACPI video bus twice
[linux-2.6.git] / drivers / acpi / video.c
index 1bdfb37..a63566b 100644 (file)
@@ -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);