[arch-general] Battery status files created on the fly?

[Wim Van Deun]

Hi Norbert,

I have the exact same issue on a dell latitude e5510 running the x86_64
kernel. And on a dell latitude 1220 running the i686 kernel.
Didn't know about the hack, thanks.

Regards,
Wim


On Tue, May 17, 2011 at 7:26 PM, Norbert Zeh <nzeh at cs.dal.ca> wrote:

> Hi folks,
>
> I've run into a weird problem with monitoring the status of my laptop
> battery.
> Since I assume I'm doing something wrong, I thought I'd ask for feedback
> here
> first before going and filing a bug report.  Here goes:
>
> When my machine boots, /sys/class/power_supply/BAT0 and all the files in it
> do
> not exist:
>
> $ ls /sys/class/power_supply
> AC
>
> Since my battery monitor uses this as the source of information, it
> obviously
> fails.
>
> Now, as soon as I query the state of the battery through
> /proc/acpi/battery/BAT0, the missing files under /sys/class/power_supply
> get
> created:
>
> $ cat /proc/acpi/battery/BAT0/state
> present:                 yes
> capacity state:          ok
> charging state:          discharging
> present rate:            1265 mA
> remaining capacity:      4234 mAh
> present voltage:         11340 mV
>
> $ ls /sys/class/power_supply
> AC  BAT0
>
> This is not just a timeout issue.  If I don't query
> /proc/acpi/battery/BAT0/state, /sys/class/power_supply/BAT0 does not get
> created even after a few hours of uptime.
>
> Also, after suspending, the files remain present but cannot be read.
>  Querying
> the battery through the /proc interface once again brings everything back
> to
> normal.
>
> Now what's funny about this is that I read online that the
> /proc/acpi/battery
> interface is deprecated and that the /sys/... interface should be used
> instead.
> Yet, without querying the former, the latter doesn't even exist.
>
> Did anybody run into similar issues?  Does anybody have any ideas how to
> fix
> this "the proper way"?  (My workaround right now is to include "cat
> /proc/acpi/battery/BAT0/state > /dev/null" in rc.local, but that's
> obviously a
> hack.)
>
> Thanks for any pointers you may give.
>
> Cheers,
> Norbert
>
> PS: Machine is Dell Latitude E6510 running 64-bit ARCH.
>