tree ac6ec8b6ac4f96ce7ef7b5e9fa057099d7ce9af1
parent 07a2039b8eb0af4ff464efd3dfd95de5c02648c6
author Zhao Yakui <yakui.zhao@intel.com> 1245122593 +0800
committer Len Brown <len.brown@intel.com> 1245814721 -0400

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>