linux-kernel - Re: [BUG] /sys/class/power_supply/BAT0/ shouldn't disappear when battery is unplugged

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Message-Id: <1240952444.3781.34.camel@maxim-laptop>
Date:	Wed, 29 Apr 2009 00:00:44 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	avorontsov@...mvista.com
Cc:	cbou@...l.ru, dwmw2@...radead.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] /sys/class/power_supply/BAT0/ shouldn't disappear when
 battery is unplugged

On Mon, 2009-04-27 at 21:49 +0400, Anton Vorontsov wrote:
> On Sun, Apr 26, 2009 at 04:36:58PM +0300, Maxim Levitsky wrote:
> > New sysfs battery interface has a flaw.
> > 
> > Suppose I removed battery from the system, and then booted it.
> > then gnome power manager has no idea that my system has battery, and
> > thus it hides battery settings.
> 
> If after insertion the battery is visible in /sys/class/power_supply/,
> then it's not a kernel bug. That's purely gnome issue (or HAL), it
> seem to not handle hot-plugged batteries.
No, I am talking about the following situation:

Suppose:

I keep battery in the closet.
I turn my system on
Gpm has no idea my system has a battery, thus it hides battery tab.
I want to set change battery settings.





> 
> > It also has a bug that prevents it from hiding battery icon, when I
> > unplug the battery, in other words, it isn't prepared for battery to
> > disappear.
> 
> Again, you should report that to HAL/Gnome maintainers, so that gnome
> power manager would handle battery removal events generated by the
> power supply class.
I did, no reaction so far...

> 
> > I think it would be nice to keep /sys/class/power_supply/BAT0/ even if
> > battery isn't present.
> 
> That isn't always possible. Imagine a battery inside some hot-pluggable
> PCI device. Or an USB device, or a battery with a built-in controller
> connected through W1 bus (i.e. batteries w/ ds2760 chip).
Ok, why not to do so for acpi devices?


> 
> > btw, there is /sys/class/power_supply/BAT0/present, thus maybe this is
> > just a bug?
> 
> Nope. And personally I think we should remove the "present"
> property, and drivers should learn to remove stuff from power_supply/
> if there is no battery inserted. But so far HAL/Gnome/whatever have
> to handle both methods.
> 
> Thanks,
> 

Best regards,
	Maxim Levitsky

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