[PATCH] ideapad: Check if acpi already handle backlight power in 'ideapad_backlight_notify_power' to avoid a page fault

Ike Panhc ike.pan at canonical.com
Sun Sep 11 06:09:40 UTC 2011

From: Rene Bolldorf <xsecute at googlemail.com>

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 at googlemail.com>
Signed-off-by: Ike Panhc <ike.pan at canonical.com>
 drivers/platform/x86/ideapad-laptop.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/platform/x86/ideapad-laptop.c b/drivers/platform/x86/ideapad-laptop.c
index 0c59541..0d94eec 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))
 	blightdev->props.power = power ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;

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