ACPI: Add the reference count to avoid unloading ACPI video bus twice

Sometimes both acpi video and i915 driver are compiled as modules.
And there exists the strict dependency between the two drivers.
The acpi video bus will be unloaded in course of unloading the i915 driver.
If we unload the acpi video driver, then the kernel oops will be triggered.

Add the reference count to avoid unloading the ACPI video bus twice.
The reference count should be checked before unregistering the acpi video bus.
If the reference count is already zero, it won't unregister it again.
And after the acpi video bus is already unregistered, the reference count
will be set to zero.

http://bugzilla.kernel.org/show_bug.cgi?id=13396

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/acpi/video.h b/include/acpi/video.h
index af6fe95fd3d0..cf7be3dd157b 100644
--- a/include/acpi/video.h
+++ b/include/acpi/video.h
@@ -3,10 +3,10 @@
 
 #if (defined CONFIG_ACPI_VIDEO || defined CONFIG_ACPI_VIDEO_MODULE)
 extern int acpi_video_register(void);
-extern int acpi_video_exit(void);
+extern void acpi_video_unregister(void);
 #else
 static inline int acpi_video_register(void) { return 0; }
-static inline void acpi_video_exit(void) { return; }
+static inline void acpi_video_unregister(void) { return; }
 #endif
 
 #endif