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

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Date:	Mon, 27 Apr 2009 21:49:37 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Maxim Levitsky <maximlevitsky@...il.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 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.

> 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 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).

> 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,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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