Re: PMBus support in Linux

[Guenter Roeck <guenter.roeck-IzeFyvvaP7pWk0Htik3J/w@public.gmane.org>]

On Sat, May 29, 2010 at 04:53:01AM -0400, Wolfram Sang wrote:
> > If there is no activity yet, question is if I should write individual drivers or 
> > if I should define a PMBus infrastructure on top of i2c/smbus first.
> > Any thoughts on which approach would be more likely to be accepted into the kernel ?
> 
> Did I get this correct: The plan is to support PMBus-devices and let them
> report their data in a hwmon-compatible-way?
> 
Yes.

> (If so, did you already check how well PMBus data maps to the
> hwmon-sysfs-interface?)
> 
Yes. PMBus uses i2c as transport, so it can use the existing i2c/smbus infrastructure. 
Data reported is voltage, temperature, current, power, and fan data as available
from the individual chip. Chips support a chip dependent number of channels.
Values reported are typically in the form of X = Y * 2^N, ie there is a mantissa
and an exponent.

So I would say it maps pretty well; I don't really see a substantial difference
to other HW monitoring chips in that respect. Key difference may be that PMBus devices 
typically also have a control component, but I don't have plans to implement that,
at least not for now.

Guenter