Re: Soliciting opinions on desired "envstat -S" behavior

[Jukka Ruohonen <jruohonen%iki.fi@localhost>]

On Fri, Mar 19, 2010 at 11:16:31PM -0500, Constantine A. Murenin wrote:
> On 19/03/2010, Paul Goyette <paul%whooppee.com@localhost> wrote:
> >  As a result, the current behavior is sub-optimal, as it removes _ALL_
> > sensor limits, regardless of whether those limits were learned from the
> > hardware driver or provided by the configuration file.  Even worse, the

This indeed makes the flag dangerous.

> >  B. Sensors that can provide initial limit values, but which cannnot
> >    handle changes to those values in hardware.  All limit processing is
> >    actually handled in the sysmon_envsys(9) framework and not in the
> >    driver or hardware.
> >
> >    The current behavior works, but I believe that we should really
> >    "re-import" the initial values from the driver/hardware.  This is
> >    closest to the documented behavior.
> 
> I disagree that the current behaviour works as documented, since it
> doesn't restore the defaults as per the driver (and it is documented
> to restore "the setting that the drivers use by default").  Therefore,
> I absolutely agree with your "re-import" proposal.

I agree with both of you. In the past some concerns have been raised about
"mangling" the limit values in sensors that have system-wide responsibilities.
If someone however decides to alter the limits in such sensors for whatever
reason, this way it would be easy to restore these to the "defaults".

> This part certainly gets complicated, and a C3 variation may sound
> like the right thing to do.  I think it would be best if the drivers
> could reset the limits internally with an appropriate reset command
> issued directly to the underlying hardware as opposed to the
> bookkeeping of the values in the software (otherwise, what would
> happen after a soft reboot?), but I'm unaware regarding whether or not
> such hardware support is usually present.

Additionally, the limit values can be in read-only registers, etc.

> I think a new option should be used for the removal of all the
> hardware-set limits (both internally from sysmon_envsys(9) and from
> the underlying hardware if the hardware-based monitoring is
> applicable), which should be separate from -S.  Perhaps it could even

I disagree for the reasons mentioned above. It is not a good idea to
possibly alter the default system behavior (e.g. gracefully shutting down
the system) with a single (unprivileged?) sensor-knob.

- Jukka.