linux-kernel - Re: ACPI fan driver: uninitialized variable when CONFIG

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Message-ID: <1368666443.2063.22.camel@rzhang1-mobl4>
Date:	Thu, 16 May 2013 09:07:23 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	linux-acpi@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: ACPI fan driver: uninitialized variable when CONFIG_PM is not
 set

Hi, Michel,

On Mon, 2013-04-29 at 05:32 -0700, Michel Lespinasse wrote:
> In the following code:
> 
> static int fan_get_cur_state(struct thermal_cooling_device *cdev, unsigned long
>                              *state)
> {
>         struct acpi_device *device = cdev->devdata;
>         int result;
>         int acpi_state;
> 
>         if (!device)
>                 return -EINVAL;
> 
>         result = acpi_bus_update_power(device->handle, &acpi_state);
>         if (result)
>                 return result;
> 
>         *state = (acpi_state == ACPI_STATE_D3 ? 0 :
>                  (acpi_state == ACPI_STATE_D0 ? 1 : -1));
>         return 0;
> }
> 
> With CONFIG_PM not set, acpi_bus_update_power() returns 0 and does not
> initialize acpi_state. This results in acpi_state being used before
> initialization.
> 
> (I found out by random chance, as I suppose people don't normally
> build without CONFIG_PM anymore ?)
> 
> I'm not sure what a proper fix would be, so I'll just report this here
> and enable CONFIG_PM locally :)
> 
thanks for your report.
please check if the following patch helps or not.
https://patchwork.kernel.org/patch/2574691/

thanks,
rui

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