linux-kernel - Re: [lm-sensors] it87 sensors need an ACPI driver (2.6.31)

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Date:	Tue, 6 Oct 2009 17:04:12 +0100
From:	Alan Jenkins <sourcejedi.lkml@...glemail.com>
To:	Michael Tokarev <mjt@....msk.ru>
Cc:	Luca Tettamanti <kronos.it@...il.com>,
	Brad Campbell <brad@...p.net.au>, lm-sensors@...sensors.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [lm-sensors] it87 sensors need an ACPI driver (2.6.31)

On 10/6/09, Michael Tokarev <mjt@....msk.ru> wrote:
> Luca Tettamanti wrote:
>> On Mon, Oct 5, 2009 at 6:42 PM, Michael Tokarev <mjt@....msk.ru> wrote:
> []
>>> Well, I just tried it here and it works here too, on 3 different
>>> asus motherboards.  But asus_atk0110 is far less useful than the
>>> it87 variant.  Yes atk0110 shows correct labels for various sensors,
>>> but for one there's no way to control fan speeds using it, at least
>>> not currently, -- something which is done by it87 easily.
> []
>> The main reason for using atk0110 is correctness: the resources are
>> claimed by ACPI, it might not be safe to touch them (for the same
>> reason two drivers are not allowed to map e.g. the same PCI BAR).
>> On newer boards the risk of collision is pretty high, since the hwmon
>> chip is used by an EC that works in background... on other boards the
>> risk is much lower since the hwmon chip doesn't seem to be probed
>> actively.
>> Anyway, as user you can override this decision with
>> "acpi_enforce_resources=lax", but _I_ wouldn't recommend it.
>
> If there's a choice between "does not work but correct" and
> "incorrect but works", i'd prefer the latter, and I'd say any
> sane person agrees.

It works fine on your system but it _doesn't_ work in the general case.

If you build a kernel with it87 and use acpi_enforce_resources=lax, it
will cause a 15 second boot delay on certain models of EeePC.  There
may be worse consequences on other machines, but that's bad enough.

So this doesn't depend on sanity, it's simply a matter of whether
you're interested enough to test "acpi_enforce_resources=lax" on your
system and identify any failures.  Most people aren't that interested.
 For the rest, there's always the option.  (Which should probably set
a TAINT flag if it doesn't already).

Thanks
Alan
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