UBUNTU: SAUCE: (drop after 3.0) ideapad: Check if acpi already handle backlight power in 'ideapad_backlight_notify_power' to avoid a page fault

This patch avoid a page fault in the ideapad-laptop extras when
turning the backlight power on or off.

Signed-off-by: Rene Bolldorf <xsecute@googlemail.com>
Signed-off-by: Ike Panhc <ike.pan@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/platform/x86/ideapad-laptop.c b/drivers/platform/x86/ideapad-laptop.c
index 0c595410e78..0d94eec00f4 100644
--- a/drivers/platform/x86/ideapad-laptop.c
+++ b/drivers/platform/x86/ideapad-laptop.c
@@ -493,6 +493,8 @@ static void ideapad_backlight_notify_power(struct ideapad_private *priv)
         unsigned long power;
         struct backlight_device *blightdev = priv->blightdev;
 
+        if (!blightdev)
+                return;
         if (read_ec_data(ideapad_handle, 0x18, &power))
                 return;
         blightdev->props.power = power ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;