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

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Message-ID: <20131124192608.GA11338@earth.universe>
Date:	Sun, 24 Nov 2013 20:26:09 +0100
From:	Sebastian Reichel <sre@...g0.de>
To:	Pali Rohár <pali.rohar@...il.com>
Cc:	Anton Vorontsov <anton@...msg.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	freemangordon@....bg, aaro.koskinen@....fi, pavel@....cz
Subject: Re: [PATCH v2 2/3] bq2415x_charger: Use power_supply notifier for
 automode

On Sun, Nov 24, 2013 at 08:01:16PM +0100, Pali Rohár wrote:
> > I'm wondering if the watchdog thread should check some values,
> > like e.g. battery temperature. It should stop charging the
> > battery if some critical battery temperature threshold is
> > reached.
> 
> For checking battery temperature is needed third driver 
> (rx51_battery.ko).

I know, but that doesn't mean one can skip the check.

> And I think this should not be implemented in driver itself but in
> charger manager framework...

There is a reason, that the HW has a watchdog. I think the safety
relevant stuff should be done in the watchdog thread. This ensures,
that charging depends on reading the safety relevant sensors.

Of course the watchdog stuff could be moved into the charger manager
framework...

> Currently on Maemo 5 this is handled in userspace (with open 
> source dsme daemon).

I assume it currently also takes care of the bq2415x watchdog? That
means if the daemon dies charging will stop, because the watchdog
does no longer trigger.

When your patch is applied you have introduced a safety issue.
When the daemon dies charging will continue and temperature is
no longer checked.

-- Sebastian

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