linux-kernel - Re: Generic battery interface

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Date:	Mon, 31 Jul 2006 04:34:15 +0300
From:	"Shem Multinymous" <multinymous@...il.com>
To:	"Valdis.Kletnieks@...edu" <Valdis.Kletnieks@...edu>
Cc:	"Vojtech Pavlik" <vojtech@...e.cz>, "Pavel Machek" <pavel@...e.cz>,
	"Brown, Len" <len.brown@...el.com>,
	"Matthew Garrett" <mjg59@...f.ucam.org>,
	"kernel list" <linux-kernel@...r.kernel.org>,
	linux-thinkpad@...ux-thinkpad.org, linux-acpi@...r.kernel.org
Subject: Re: Generic battery interface

On 7/31/06, Valdis.Kletnieks@...edu <Valdis.Kletnieks@...edu> wrote:
> OK, if you meant this one (that hadn't shown up here before I hit 'send'):

No, I ment this one: http://lkml.org/lkml/2006/7/30/193
(or actually its parent, at the time).

> was commenting about.  A gkrellm-ish program can query every 100ms and
> get a cached value 49 times out of 50 for a value that's hardware-updated
> every 5 seconds, and all will be well (of course, there's room for some
> added optimization,

That's exactly what we're trying to avoid -- excessive polling of
values that don't change. It causes unnecessary system load and timer
interrupts on tickless kernels.

> unless the kernel has
> a good way to pass back a good hint of when the next update will be...)

The kernel often doesn't know when it will get the next update. But on
the other hand, apps usually know well in advance  when they'll *want*
the next update. My proposal exploits this to get optimal behavior (if
the driver+infrastructure do the right thing).

  Shem
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