linux-kernel - Re: [PATCH v4 2/4] power: supply: core: add input voltage/current measurements

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Message-ID: <20200503000921.6krrkai7onsba2uz@earth.universe>
Date:   Sun, 3 May 2020 02:09:21 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v4 2/4] power: supply: core: add input voltage/current
 measurements

Hi,

On Sun, May 03, 2020 at 01:11:58AM +0200, Michał Mirosław wrote:
> On Sun, May 03, 2020 at 12:45:26AM +0200, Michał Mirosław wrote:
> > On Sun, May 03, 2020 at 12:23:49AM +0200, Sebastian Reichel wrote:
> > > On Fri, May 01, 2020 at 05:11:18PM +0200, Michał Mirosław wrote:
> [...]
> > > > --- a/include/linux/power_supply.h
> > > > +++ b/include/linux/power_supply.h
> > > > @@ -127,7 +127,9 @@ enum power_supply_property {
> > > >  	POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX,
> > > >  	POWER_SUPPLY_PROP_CHARGE_CONTROL_START_THRESHOLD, /* in percents! */
> > > >  	POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD, /* in percents! */
> > > > +	POWER_SUPPLY_PROP_INPUT_CURRENT_NOW,
> > > 
> > > What:           /sys/class/power_supply/<supply_name>/current_avg    
> > > Date:           May 2007
> > > Contact:        linux-pm@...r.kernel.org                          
> > > Description:                  
> > >                 Reports an average IBUS current reading over a fixed period.   
> > >                 Normally devices will provide a fixed interval in which they   
> > >                 average readings to smooth out the reported value.             
> > >                                                                                 
> > >                 Access: Read    
> > >                 Valid values: Represented in microamps
> > > 
> > 
> > There are two entries for /sys/class/power_supply/<supply_name>/current_avg
> > in the file, the other one mentions IBAT instead. "voltage_now" has the
> > same problem.
> [...]
> 
> So the general idea of the sysfs API seems to require separate devices for the
> input (charger) and battery elements.
>
> Since what I'm looking at is an integrated battery controller
> (bq25896) which has three connections: an USB power (VBUS), a
> battery and the system load, but it creates only a single
> power-class device.

power-supply exposes either TYPE_MAINS/TYPE_USB or TYPE_BATTERY.
If a device is combined function, then it should register two
power-supply devices.

> This is complicated by the fact that this is an OTG device and so
> it can sink or source VBUS power.

Ok.

-- Sebastian

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