ideapad: Check if acpi already handle backlight power to avoid a page fault

commit d4afc7754a60b885b63ef23fd194984e2d53a4e6 upstream.

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: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Tested-by: Artem X <artem.brz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/platform/x86/ideapad-laptop.c b/drivers/platform/x86/ideapad-laptop.c
index 0c595410e78897e8b6b3f4b9e9c84e765ac0ba57..0d94eec00f4d8d4ec5ed1081d868cb0536083cb8 100644 (file)
--- 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;