linux-kernel - Re: x86/hwmon: conditionalize coretemp's dependency on PCI

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Message-ID: <20100928172023.75607337@endymion.delvare>
Date:	Tue, 28 Sep 2010 17:20:23 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Jan Beulich <JBeulich@...ell.com>,
	"r.marek@...embler.cz" <r.marek@...embler.cz>,
	"fenghua.yu@...el.com" <fenghua.yu@...el.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: x86/hwmon: conditionalize coretemp's dependency on PCI

On Tue, 28 Sep 2010 05:00:00 -0700, Guenter Roeck wrote:
> On Tue, Sep 28, 2010 at 03:17:59AM -0400, Jean Delvare wrote:
> > Do you mean it is strange from a technical perspective, or do you have
> > evidences that it doesn't work properly? This trick come from Intel
> > themselves, I would guess they know their business.
>
> From a technical perspective. Hard to see what a PCI bridge ID has to do with Tjmax.

I agree. If you search the archives, you'll see I emitted exactly the
same complaint back then.

> > (...)
> > Higher or lower doesn't make a difference. As long as the coretemp
> > driver doesn't properly report the temperature values as being
> > relative, users don't expect the value to change depending on the
> > kernel version or configuration options. We have had dozens of user
> > reports because of this.
> > 
> You are right, functionality would change if someone runs a kernel with PCI undefined 
> on the specific systems which do use the PCI bridge ID to determine Tjmax. So 
> if there are no other options, maybe the big fat warning in that case would make sense.
> I would definitely prefer that over disabling coretemp entirely just because it _might_
> possibly report a wrong Tjmax (which it doees anyway for many CPUs).

I fully agree.

-- 
Jean Delvare
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