linux-kernel - Re: [POWER] battery calibration parameters from sysfs

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Date:	Tue, 8 Dec 2009 10:28:12 +0000
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Brian Swetland <swetland@...gle.com>
Cc:	Rebecca Schultz Zavin <rebecca@...roid.com>,
	Mike Lockwood <lockwood@...roid.com>,
	Linus Walleij <linus.walleij@...ricsson.com>, cbou@...l.ru,
	dwmw2@...radead.org, LKML <linux-kernel@...r.kernel.org>,
	linux-embedded@...r.kernel.org
Subject: Re: [POWER] battery calibration parameters from sysfs

On Mon, Dec 07, 2009 at 09:27:20PM -0800, Brian Swetland wrote:
> On Mon, Dec 7, 2009 at 8:56 AM, Mark Brown

> > I don't think the existing Android devices are much of an issue here,
> > it's not as though end users have the ability modify the firmware on
> > them (modulo the fairly small number of ADP devices).  This is an issue
> > for people producing new devices who are already going to be doing some
> > development to get the kernel up and running on their hardware.

> My preference, from an Android point of view, would be to make sure we
> have some reasonable userspace abstraction and provide a default
> implementation that will do the right thing with an intelligent
> battery driver (our usual design for inhouse work).  Then alternative
> implementations can be plugged in, should that not be sufficient.

It proably makes sense to have some of the performance tracking in there
by default - while there are some systems out there which are able to do
high quality battery tracking there's several previous generations of
monitoring technology out there which have substantial accuracy issues
(especially in the face of removable battery packs) but which will
report information to userspace.  This makes it unwise to rely to
totally on the information you're getting from the kernel - the
smartness of a smart battery driver can vary greatly.
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