linux-kernel - Re: [PATCH] misc,acpi,backlight: MSI S270 Laptop support

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Date:	Tue, 3 Oct 2006 21:37:29 -0400
From:	Dmitry Torokhov <dtor@...ightbb.com>
To:	Lennart Poettering <mzxreary@...inter.de>
Cc:	len.brown@...el.com, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH] misc,acpi,backlight: MSI S270 Laptop support

On Tuesday 03 October 2006 21:28, Lennart Poettering wrote:
> On Mon, 02.10.06 22:27, Dmitry Torokhov (dtor@...ightbb.com) wrote:
> 
> > > +        ret = sysfs_create_group(&msipf_device->dev.kobj, &msipf_attribute_group);
> > > +        if (ret)
> > > +                goto fail_platform_device;
> > > +
> > > +
> > > +        /* Enable automatic brightness control again */
> > > +        if (auto_brightness != 2)
> > > +                set_auto_brightness(1);     
> > > +
> > 
> > What happens if auto_brightness is 2 but userspace messed up with it
> > through device's sysfs attribute? 
> 
> If auto_brightness is 2 we assume that the user doesn't want the
> module to fiddle with the automatic brightness control
> automatically. So we don't do it, neither when loading nor when
> unloading the module. However, if the user wants to fiddle with the
> setting through sysfs he may do so and we will not reset his changes
> when unloading the module. This allows the user to do something like
> this to disable the brightness control without having the the driver
> loaded the whole time:
> 
>   modprobe msi-laptop auto_brightness=2 && echo 0 > /sys/devices/platform/msi-laptop-pf/auto_brightness && modprobe -r msi-laptop
> 
> If auto_brightness is 1 or 0, we do as requested but reset the control
> to the bootup default when unloading. (i.e. enable it again)

Normally drivers clean up after themselves as if they were never loaded,
taht is why I questioned partial cleanup.

-- 
Dmitry
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