linux-kernel - Re: libbattery was Re: [RFC PATCH 5/5] power: generic-adc-battery: Add capacity handling

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Date:   Wed, 18 Oct 2017 17:52:22 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Tony Lindgren <tony@...mide.com>,
        Sebastian Reichel <sebastian.reichel@...labora.co.uk>,
        pali.rohar@...il.com, sre@...nel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-omap@...r.kernel.org, khilman@...nel.org,
        aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
        patrikbachan@...il.com, serge@...lyn.com, abcloriens@...il.com,
        clayton@...ftyguy.net, martijn@...xit.nl,
        sakari.ailus@...ux.intel.com,
        Marek Belisko <marek.belisko@...n-nandra.com>,
        robh+dt@...nel.org, linux-pm@...r.kernel.org,
        Marek Belisko <marek.belisko@...il.com>
Subject: Re: libbattery was Re: [RFC PATCH 5/5] power: generic-adc-battery: Add capacity handling


> Am 18.10.2017 um 15:56 schrieb Pavel Machek <pavel@....cz>:
> 
> On Wed 2017-10-18 06:22:04, Tony Lindgren wrote:
>> * H. Nikolaus Schaller <hns@...delico.com> [171018 05:49]:
>>>> Am 18.10.2017 um 14:28 schrieb Pavel Machek <pavel@....cz>:
>>>> 
>>>> So I started something, it is at.
>>>> 
>>>> https://github.com/pavelmachek/libbattery
>>>> 
>>>> My battery on n900 is currently uncalibrated (and charging), still it
>>>> gets some kind of estimation:
>>>> 
>>>> Battery -1 %
>>>> Seconds -1
>>>> State 1
>>>> Voltage 3.88 V
>>>> Battery 63 %
>>>> 
>>>> Of course, there's a lot more work to be done.
>>> 
>>> Nice start but not a solution to our problem.
>>> 
>>> Our problem is that people simply expect that for example https://packages.debian.org/wheezy/xfce/xfce4-battery-plugin
>>> displays the battery percentage.
>> 
>> I think we could make things compatible with various battery apps by
>> having libbattery write back the capacity percentage and time remaining
>> to the kernel driver via sysfs or a dev entry. Then the kernel interface
>> can just display the data to whatever apps.
> 
> Hmm. This could be as simple as providing symlink from
> /sys/class/power/userland-battery to some place writable by
> userspace...

Well, please implement arbitrary symlinks in /sysfs...

root@...ux:~# ln -sf /tmp/somewhere /sys/class/power_supply/fake-battery
ln: failed to create symbolic link '/sys/class/power_supply/fake-battery': Operation not permitted
root@...ux:~#

And you need to run a daemon so that the data is available
somewhere.

BR and thanks,
Nikolaus


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