Bug#655377: [3.0 -> 3.1 regression] Kernel panic when turning off screen backlight using laptop Fn key
tags 655377 + patch moreinfo
Jonathan Nieder wrote:
> Artem X wrote:
>> Hello, there's patch available to fix the kernel panic when 'turning
>> off screen backlight'
>> which me and other people experienced (on various distros including
>> debian testing on lenovo).
> Might be fixed by v3.2-rc1~111^2~22 (ideapad: Check if acpi already
> handle backlight power to avoid a page fault, 2011-10-23). Could you
> try a 3.2.y release candidate from experimental to check?
Even better, please try this patch against a 3.1.y kernel.org kernel.
Instructions for testing a patched kernel are at .
If it works, we can send it to Greg to consider applying to the 3.1.y
Luckily the ideapad-laptop backlight driver was only introduced in
v3.1-rc1~14^2~29, so older kernels do not have this bug.
-- >8 --
From: Rene Bollford <firstname.lastname@example.org>
Date: Sun, 23 Oct 2011 09:56:42 +0200
Subject: 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 <email@example.com>
Signed-off-by: Matthew Garrett <firstname.lastname@example.org>
Signed-off-by: Jonathan Nieder <email@example.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 0c595410e788..0d94eec00f4d 100644
@@ -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)
if (read_ec_data(ideapad_handle, 0x18, &power))
blightdev->props.power = power ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;