Re: [PATCH] ACPI: Clarify resource conflict message

[Jean Delvare <jdelvare@suse.de>]

Hi Len,

Le lundi 31 août 2009, Len Brown a écrit :
> > > The message "ACPI: Device needs an ACPI driver" is misleading...
> 
> > > ACPI: Device may still be supported by an ACPI driver
> 
> > I would drop the word "still", but otherwise I think this is a good idea.
> 
> I agree we need to clarify this message.
> 
> Right now we have (copied from a recent bug report):
> 
> w83627ehf: Found W83627EHG chip at 0x290
> ACPI: I/O resource w83627ehf [0x295-0x296] conflicts with ACPI region SEN1
> [0x295-0x296]
> ACPI: Device needs an ACPI driver
> 
> This results in people filing bugs against ACPI because their sensor
> driver does not load -- we've seen several already.

I know, and this is why I sent a patch to change the wording.

> I'm okay with the 1st ACPI line -- it tells somebody who cares exactly
> what is going on.
> 
> "Device needs an ACPI driver", however, fails to tell the administrator
> what they can do about it.  We should probably mention that they
> can test "acpi_enforce_resources=lax".  However, we should probably
> put a big WARNING - using-at-own-risk note in the dmesg when
> that option is actually used.

I don't think we want to unconditionally point the user to
"acpi_enforce_resources=lax". Doing so would essentially void our
effort to get rid of concurrent access to these resources.

In particular, now that we have the asus_atk0110 driver and this
driver loads automatically on the boards which need it, we certainly
do NOT want to tell these users that they should use
"acpi_enforce_resources=lax". What they should do is use the
asus_atk0110 driver instead of the native driver they were using so
far.

Only if no ACPI-based hardware monitoring driver has been loaded, we
could point the user to "acpi_enforce_resources=lax". With a warning
and disclaimer, of course.

> And then what is the next course of action -- possible inclusion
> on a white-list if they conflict turns out to be benign,
> or (less likely) possible development of a missing ACPI driver?

I wasn't sure whether you would be OK with a whitelist. I too
think we will need one, although this won't be in 2.6.31. Then it
indeed makes sense to ask the users to test
"acpi_enforce_resources=lax", and if it works, they can report to us
and after a DSDT code review, their system can be added to the
whitelist.

I am curious how many systems will have to be added to the whitelist.
I presume that the whitelist would consist in DMI board vendor +
model entries?

> We could have quite a few bug reports filed on this,
> so wording is important.

I fully agree.

What I propose:
* For 2.6.30 (if we are fast enough), an updated version of my patch,
  taking Alan Jenkins' suggestion into account, and an additional
  warning when "acpi_enforce_resources=lax" is used.
* For 2.6.31, a whitelisting mechanism, and a verbose log message
  explaining the steps to get a system into this whitelist.

OK?

Thanks,
-- 
Jean Delvare
Suse L3
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