linux-kernel - Re: [PATCH v2 2/3] bq2415x_charger: Use power

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Date:	Mon, 25 Nov 2013 22:50:01 +0100
From:	Sebastian Reichel <sre@...g0.de>
To:	Ивайло Димитров 
	<freemangordon@....bg>
Cc:	pavel@....cz, pali.rohar@...il.com, anton@...msg.org,
	dwmw2@...radead.org, tony@...mide.com, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	aaro.koskinen@....fi
Subject: Re: [PATCH v2 2/3] bq2415x_charger: Use power_supply notifier for
 automode

Hi,

On Mon, Nov 25, 2013 at 08:32:46PM +0200, Ивайло Димитров wrote:
> So, AIUI there are 2 options:
> 
> 1. charger driver polls the battery driver every n (60?) seconds.
> 2. battery driver sends PSY_EVENT_PROP_CHANGED on every degree
>    up or down.
>  
> In both cases if the temperature is outside of the safe margins, the
> charging should be stopped.

ACK.

> 2 seems more generic to me, but as rx51-battery is missing the
> functionality to send events on temperature change, I guess 1 will
> be easier to implement.

The temperature must be polled anyway, if the ADC does not support
interrupts.

> And I think there should be some method (sysfs entry?, /dev/bqxxx
> opened?) to tell the charger driver to stop polling the battery 
> driver once (and if) the userspace has started to take care of the 
> battery temperature - makes no sense to duplicate the checks IMO.

I would just cache the temperature value in the battery driver for a
couple of seconds. Then userspace can check for very high temperatures
(-> system shutdown) and the charging driver can check for
temperatures, which are critical for charging.

-- Sebastian

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