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

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Message-ID: <20131124210041.GA12180@earth.universe>
Date:	Sun, 24 Nov 2013 22:00:43 +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 08:41:46PM +0100, Pali Rohár wrote:
> On Sunday 24 November 2013 20:26:09 Sebastian Reichel wrote:
> > On Sun, Nov 24, 2013 at 08:01:16PM +0100, Pali Rohár wrote:
> > > 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
> 
> No dsme checking battery temperature and does not handle bq24510 
> timer (previously this was in closed bme daemon which 
> functionality is now in kernel drivers).

Ok, so then the temperature checks are done by bme.

> But dsme daemon also kicking tlw4030 watchdog, so when daemon dies
> after 30s tlw4030 reboot device.

Yes, but that does not matter if it does not take care of the
charging. If the dsme daemon is not started for some reason
phone will not be rebootet and phone charges.

> But right you can implement correctly this in userspace (e.g. 
> when daemon not running/crashed, you can restart daemon or reboot 
> system or disable charing, whatever...) and you do not need to 
> have it in kernel...

That does not change the fact, that the kernel openes a safety issue
in default configuration. To be on the safe side charging must be
disabled until some safety checking daemon enables it.

-- Sebastian

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