sysmon_envsys - Setting sensor on-chip thresholds from userland

[Paul Goyette <paul%whooppee.com@localhost>]

I'm working on a driver for On-DIMM temperature sensors for memory 
modules, similar to OpenBSD's sdtemp but with sysmon_envsys(9) support.

These sensors have on-chip limit registers for a Lower, Uppper, and 
Critical boundary setting, and have on-chip comparison and flag-bit 
setting when the actual temp transitions from one zone to another.
(The sensor chips also have an event output pin, which might be able to 
generate an I2C interrupt, but that's a question for another day!)

I've been muddling through the sysmon_envsys stuff, and I'm having 
difficulty understanding how a userland program might provide some 
threshold values to the driver.  Would it be correct (or at least 
acceptable) for the driver's sensor refresh routine to grovel through 
the sensor's event queue to find the values associated with certain 
monitor types (ie, ENVSYS_FMONWARNUNDER, WARNOVER, and CRITOVER)?

I'm also a bit more confused about all this, since the example in the 
sysmon_envsys(9) man page seems to use a hard-wired threshold for 
setting the sensor state, rather than using a limit from userland.

Any guidance in this area would be greatly appreciated.


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