linux-kernel - Re: [PATCH 5/5] power_supply: add a charge_type status to the api, and use it for olpc driver

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Message-ID: <20090630191547.GA24002@rakim.wolfsonmicro.main>
Date:	Tue, 30 Jun 2009 20:15:47 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Anton Vorontsov <avorontsov@...mvista.com>
Cc:	Andres Salomon <dilinger@...labora.co.uk>, cbou@...l.ru,
	dwmw2@...radead.org, linux-kernel@...r.kernel.org,
	richard@...top.org, Andrew Morton <akpm@...ux-foundation.org>,
	Paul Fox <pgf@...top.org>, dsaxena@...top.org
Subject: Re: [PATCH 5/5] power_supply: add a charge_type status to the api,
 and use it for olpc driver

On Tue, Jun 30, 2009 at 11:02:39PM +0400, Anton Vorontsov wrote:
> On Tue, Jun 30, 2009 at 04:57:14PM +0100, Mark Brown wrote:

> > I strongly suspect you will find that the "slow" mode there is actually
> > a trickle charge.  It's a lot more practical to trickle charge in mobile
> > phone sized systems since the batteries are so much smaller than laptop
> > batteries. 

...

>  For a Li-ion battery, the precharge current is typically 0.1C
>  (C = charge rate = the charge current which will fully charge the
>  battery in one hour)."

Yup, that sounds like a trickle charge all right.

> There is also precharge-wait and fastcharge-wait modes, FWIW.
> But we don't expose this information to the userspace.

Those *probably* boil down to one of the other states - without looking
at the datasheet they sound like waiting for the conditions required to
do one of the other charges to be satisfied.

> Probably not, Fast/Slow/Trickle are quite vague terms anyway.
> I'd prefer if we could measure this in some real units, but alas...

Fast and trickle charge are fairly well understood terms, I think.  For
specific numbers you'd need to look at the particular batteries
involved, unfortunately, but they do tend to be fairly obvious when
looking at a particular charger and/or battery.
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