linux-kernel - Re: [lm-sensors] [PATCH 1/3] hwmon: Driver for SMM665 Six-Channel Active DC Output Controller/Monitor

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Date:	Sat, 19 Jun 2010 10:27:29 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	guenter.roeck@...csson.com
Cc:	Jonathan Cameron <jic23@....ac.uk>,
	Hans de Goede <hdegoede@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>
Subject: Re: [lm-sensors] [PATCH 1/3] hwmon: Driver for SMM665 Six-Channel 
 Active DC Output Controller/Monitor

On Fri, 18 Jun 2010 12:13:25 -0700, Guenter Roeck wrote:
> On Fri, 2010-06-18 at 14:10 -0400, Jonathan Cameron wrote:
> > Another quick query.  Are the _min / _max attributes as defined in the
> > abi meant for alarms?  I always thought they were to tell userspace the
> > limits on measurement?
> > 
> Good question. I thought it is supposed to refer to alarm limits, but I
> may be wrong. 
> 
> Browsing through a couple of drivers, it _looks_ like the values are
> used for alarm limits (eg adm1025 or lm85). Limits are not always set to

Yes, these are alarms. _min and _max are really misnomers, these should
have been _low and _high but by the time I realized it, _min and _max
were already de facto standards and it was too late to change this.

Documentation/hwmon/sysfs-interface says:

Usual items are "input" (measured value), "max" (high threshold,
"min" (low threshold).

Specific occurrences are then left without details. If you think this
document can be improved, I welcome patches.

> useful values, though. This is what my CPU board returns:
> 
> lm85-i2c-0-2e
> Adapter: SMBus PIIX4 adapter at 0580
> V1.5:        +1.80 V  (min =  +0.00 V, max =  +3.32 V)   
> VCore:       +1.29 V  (min =  +0.00 V, max =  +2.99 V)   
> V3.3:        +3.32 V  (min =  +0.00 V, max =  +4.38 V)   
> V5:          +5.00 V  (min =  +0.00 V, max =  +6.64 V)   
> V12:        +12.12 V  (min =  +0.00 V, max = +15.94 V)   
> 
> The lm85 datasheet says: "If a voltage input either exceeds the value
> set in the voltage high limit register or falls below the value set in
> the voltage low limit register, the corresponding bit will be set
> automatically by the LM85 in the interrupt status registers (41-42h)."
> 
> > Either way, one of us has misunderstood so perhaps the documentation needs
> > to be more specific....
> 
> Agreed.

-- 
Jean Delvare
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