linux-kernel - Re: [PATCH 1/2] hwmon: Enhance the sysfs API for power meters.

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Message-ID: <20090812115653.GJ24339@elf.ucw.cz>
Date:	Wed, 12 Aug 2009 13:56:54 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Darrick J. Wong" <djwong@...ibm.com>
Cc:	Len Brown <lenb@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	lm-sensors <lm-sensors@...sensors.org>,
	linux-acpi <linux-acpi@...r.kernel.org>,
	Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH 1/2] hwmon: Enhance the sysfs API for power meters.

On Mon 2009-08-10 14:12:11, Darrick J. Wong wrote:
> On Sat, Aug 08, 2009 at 11:48:30PM +0200, Pavel Machek wrote:
> > 
> > Uhuh. This is hwmon documentation AFAICT; so a) it should be
> > documented here, and b) interface should be generic so that it works
> > without ACPI, too.
> 
> Perhaps it is time to set up a netlink interface for all the hwmon drivers?
> >From what I can tell, some of the chips can send interrupts when alarms go off,
> though I don't see much of an effort by the drivers to catch those interrupts.
> For sure there's no netlink socket that one can read for that sort of thing; a
> far as I can tell, client programs are expected to bang on sysfs periodicially
> to figure out when things have gone bad.

Is netlink right interface for that? Perhaps /sys files should be
pollable?

> > > The ACPI spec is silent on this matter.  It's not clear if the OS is supposed
> > > to monitor and take action on its own when power > cap, or if the hardware/BIOS
> > > will take action, or possibly both...?
> > 
> > Having user<->kernel interface that is well... uh... undocumented
> > makes little sense.
> 
> So it goes with ACPI.  Given that things like Node Manager and Active Energy
> Manager claim to be able to control power use, I would guess that it is
> generally likely that a power monitoring system would take action on its own to
> cut power use, and not necessarily bothering to tell the OS exactly what it's
> doing.

I guess this needs to be clarified/documented properly because it
should go anywhere near mainline.
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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