linux-kernel - RE: Thermal kernel events API to userspace - Was: Re: thermal: Avoid CONFIG

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Message-ID: <D6D887BA8C9DFF48B5233887EF046541094488C0CB@bgsmsx502.gar.corp.intel.com>
Date:	Tue, 25 Jan 2011 16:44:54 +0530
From:	"R, Durgadoss" <durgadoss.r@...el.com>
To:	Thomas Renninger <trenn@...e.de>,
	"Zhang, Rui" <rui.zhang@...el.com>
CC:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	"jdelvare@...ell.com" <jdelvare@...ell.com>,
	Len Brown <lenb@...nel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>,
	"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-trace-users@...r.kernel.org" 
	<linux-trace-users@...r.kernel.org>
Subject: RE: Thermal kernel events API to userspace - Was: Re: thermal:
 Avoid CONFIG_NET compile dependency

Hi Thomas,

> 
> I wonder which events would need userspace to take specific
> (configured) actions at all and what kind of action it could be.
> 
> What is THERMAL_USER_AUX0?
> When will it get thrown and what is userspace expected to do?
> 

This THERMAL_USER_AUX0 is meant for the DTS core thresholds.
In ACPI compliant systems, There are two core thresholds, that
Can be programmed and read via IA32_THERM_INTERRUPT MSR. One is the
Lower threshold (AUX0) and the other one is the higher threshold(AUX1).

When the Current temperature goes below the lower threshold, or above
the higher threshold, the HW generates an interrupt. This is what is
forwarded to the user space through the netlink events.

The user app can increase performance(increase CPU speed..)
on receiving AUX0 events, and try to reduce performance
(like CPU frequency reduction, display control..)on getting AUX1 events.
Basically, the app can do anything to reduce the temperature of the
Platform.

Thanks,
Durga