I agree with your approach, below is a new patch which apply clean on
top of v3.1-rc3.
Best regards
René
---
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))
return;
blightdev->props.power = power ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
--
On Wed, Aug 24, 2011 at 5:12 AM, Ike Panhc <[email protected]> wrote:
> Nice done. Thanks for finding the bug. I write most part of ideapad-laptop.c
> though the maintainer is still Matthew.
>
> I think the patch attached below is much simple and we can avoid unnecessary
> read_ec_data if blightdev is not set. Since you are the one who find the bug
> and have the first patch, I would like to keep you as author and your sign
> off. Of course I need your agree. (Hoping I do not break the sign-off rule)
>
> Please review the patch below and reply if you agree with this or disagree.
>
>
> Hi Matthew,
>
> When acpi_backlight=video, priv->blightdev will be NULL and use it without
> checking will cause kernel oops. I suggest we shall have the fix in v3.1
> cycle.
>
>
> ====== 8< ======
>
> From 8bd37cd5da31abaca4b906bc84eb45a0834678ea Mon Sep 17 00:00:00 2001
> From: Rene Bolldorf <[email protected]>
> Date: Wed, 24 Aug 2011 09:56:24 +0800
> Subject: [PATCH] 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 <[email protected]>
> Signed-off-by: Ike Panhc <[email protected]>
> ---
> 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))
> return;
> blightdev->props.power = power ? FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
> --
> 1.7.5.4
>
>
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