[lm-sensors] Adding critical/fault limits to hwmon sysfs API

Jean Delvare khali at linux-fr.org
Wed Jun 23 14:43:46 CEST 2010

Hi Guenter,

On Sun, 20 Jun 2010 09:37:59 -0700, Guenter Roeck wrote:
> the current hwmon sysfs API does not specify critical or fault limits for voltage
> and current readings.
> Many recent power controller/monitoring chips have support for such limits in addition
> to alarm limits. Typical action, when a the critical or fault limit is reached,
> may be a board reset or power shutdown, or to report the fault condition.
> Examples for chips supporting critical/fault limits are SMM665 and variants as well
> as many PMBus devices, such as MAX8688, MAX16064, LTC2978, and others.
> I think it would make sense to add critical/fault limits to the hwmon sysfs API,
> to be able to report those limits if supported by a chip.
> Any thoughts on this ?

I agree it would be good to have standard names (and libsensors
support) if these features are popular. It might be a little difficult
to come up with the right attribute names though.

For temperatures, we have temp[1-*]_crit, for the critical limit on the
high end. We don't have a name for the critical limit on the low end,
because no chip ever implemented that. The name we chose doesn't offer
much possibilities for a nice name while staying consistent. Maybe
"lcrit" would be acceptable for the low end critical limit, and we keep
"crit" for the high end critical limit?

Jean Delvare

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