ACPI: thinkpad-acpi: allow use of CMOS NVRAM for brightness control

It appears that Lenovo decided to break the EC brightness control interface
in a weird way in their latest BIOSes.  Fortunately, the old CMOS NVRAM
interface works just fine in such BIOSes.

Add a module parameter that allows the user to select which strategy to use
for brightness control: EC, NVRAM, or both.  By default, do both (which is
the way thinkpad-acpi used to work until now) on IBM ThinkPads, and use
NVRAM only on Lenovo ThinkPads.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 5197f9b9b65d..aaaa61ea4217 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -150,6 +150,7 @@ config THINKPAD_ACPI
         depends on X86 && ACPI
         select BACKLIGHT_CLASS_DEVICE
         select HWMON
+        select NVRAM
         ---help---
           This is a driver for the IBM and Lenovo ThinkPad laptops. It adds
           support for Fn-Fx key combinations, Bluetooth control, video