Luca Tettamanti wrote:
The following patch changes the default for "acpi_enforce_resources" option to
"strict", disallowing access by native drivers to IO ports and memory regions
claimed by ACPI firmware.
Hi Luca (et all)
I know it was me who proposed to send a mail about this to the ACPI list, but
when I did I had an RFC mail in mind, not a patch.
I've been discussing this with Jean Delvare (he is back from his holliday), and
he agrees that in the end this is the right thing to do. But this will probably
stop the smbus controller drivers (Jean is the i2c subsystem maintainer) from
loading on quite a few motherboards. Given that ACPI claims it is using these,
this would actually be a good thing, but still it will probably make for a lot
of unhappy users. So his call (and I support him there) is that it is too early
to do that.
<Intermezzo to get those not involved in earlier discussion up to speed>
For those not familiar with the hwmon subsystem. Some (one or 2?) release ago a
couple of new acpi functions were added:
acpi_check_resource_conflict()
acpi_check_region()
acpi_check_mem_region()
Which can be called by drivers to see if they are not trying to do IO to any
ranges claimed by ACPI.
I did a full grep for these in 2.6.28, and they are only used by the smbus /
i2c controller drivers there. In 2.6.29 the hwmon drivers for the hwmon part of
superio IC's starts checking these too.
The behaviour of these 3 functions gets controlled by the global
acpi_enforce_resources kernel (cmdline) option (and changing this from lax to
strict will only influence these 3 methods). The default currently is lax,
which will cause these methods to only issue a warning about conflicts, but not
report any actual conflicts to the caller. Changing this to strict would
actually report the conflict, stopping the smbus drivers (and hwmon superio)
drivers from loading. As said before: Given that ACPI claims it is using these,
this would actually be a good thing. But it is a change from current behaviour
so quite some people will probably start yelling.
</intermezzo>
So back to the discussion about changing the default of acpi_enforce_resources
to strict, Jean and I have been discussing this on IRC and we feel it will most
likely cause too much pain. So we would like to suggest to make the default
depend up on the motherboard. Our plan is to have the default be "auto" and
that will mean "lax", unless the motherboard is atk0110 (Asus ACPI interface
for reading hwmon data) capable and in that case "auto" will mean "strict"
The plan is then to merge this acpi subsystem change and the atk0110 driver at
the same time, so that people will get different hwmon capabilities, but won't
loose hwmon capabilities all together. Important note: this is meant as an
temporary state of affairs, the end goal is to make the checking strict.
Luca do you think you could do a patch implementing the described "auto" value
for acpi_enforce_resources ?
ACPI people, would this be acceptable as a temporary solution ?
Thanks & Regards,
Hans
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