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 18:48:36 +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 18:13 schrieb Pavel Machek <pavel@....cz>:
> 
> On Wed 2017-10-18 17:52:22, H. Nikolaus Schaller wrote:
>> 
>>> 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...
> 
> Any reason why I'd like to do that?

I don't know if you like it or not.

But it appears to be a strict necessity to make your proposal of
"as simple as providing symlink from /sys/class/power/userland-battery
to some place writable by userspace" work.

So if a different solution to provide /sys/class/power/*-battery
is possible, it should probably be preferred and nobody will ask
you to do something you don't like.

BR,
Nikolaus


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