Re: [lm-sensors] Intel Core voltage monitoring

[Peter Ganzhorn <peter.ganzhorn@googlemail.com>]

This sounds quite interesting to me - do you think it should be possible 
to find out what's the matter about the removal of the driver and would 
I have been able to access my smbus and the hwmon chip in my laptop with it?
It would be great to have a driver for this stuff, but it should work 
flawlessly of course...and if it was removed I suppose there was a 
problem with it :(

But thanks for the info, please keep me up2date if you're going to 
investigate a bit more!

Peter


Jean Delvare wrote:
> On 12 Dec 2007 01:39:30 -0500, linux@horizon.com wrote:
>   
>>> You're not missing any driver. What you're missing is the SMBus master
>>> device itself, because it was hidden from you by the BIOS, but given
>>> what the BIOS does with it, that's the only safe approach.
>>>       
>> I don't see a Linux driver for it, but there is a spec for SMBus
>> access via ACPI, which could synchronize with SMM properly.
>>
>> The spec's at http://www.smbus.org/specs/
>> specifically
>> SMBus Control Method Interface Specification, version 1.0
>> http://www.smbus.org/specs/smbus_cmi10.pdf
>>
>> Supposedly there should be something like
>>
>> Device(SMB<id>){
>>    Name(_HID, "SMBUS01")   // Hardware ID (PnP ID)
>>    Name(_UID, <uid>)       // Unique Identification
>>    Method(_SBI, 0) {...}   // SMBus Information
>>    Method(_SBR, 3) {...}   // SMBus Data Read
>>    Method(_SBW, 6) {...}   // SMBus Data Write
>>    Method(_SBT, 6) {...}   // SMBus Data Transfer
>>    Method(_SBA, 0) {...}   // SMBus Alert Information
>> }
>>     
>
> There has been a driver doing that in kernel 2.6.18 to 2.6.22, named
> i2c_ec:
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=history;f=drivers/acpi/i2c_ec.c
> But then the driver we deleted by Len Brown. As the log message is
> empty, I can't tell you why the driver was deleted.
>
> Note that this driver was looking for an ACPI device named "ACPI0001",
> not SMB<id> as you described above. So maybe it's something different,
> I don't know.
>
>   
>> Does anyone know the right incanation (probably using "acpidump")
>> to see if this is supported on the problematic machines?  If so,
>> writing a driver becomes an interesting question.
>>     
>
> Yes, acpidump should tell you. Or just run "iasl -d" on your DSDT
> table, I guess that this is where the device in question would be
> declared. But I don't remember ever seeing the above implemented in any
> ACPI DSDT I've disassembled.
>
> I'm not sure why this would be more robust to SMM than any other driver
> though. How could the ACPI code synchronize with SMM given that you do
> not know when an SMI happens?
>
>   
>> (This seems rather obvious, so I hope this idea hasn't been
>> discarded already for some reason I have overlooked.)
>>     
>
> There clearly is a need for this on some machines, but it remains to be
> understood why the Linux ACPI people apparently do not want to expose
> this interface.
>
>   


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