Re: [lm-sensors] [RFC] [PATCH] hwmon: Add LTC4245 driver

[Hans de Goede <hdegoede@redhat.com>]

Jean Delvare wrote:
> On Sun, 12 Oct 2008 12:12:19 +0200, Hans de Goede wrote:
>> Ira Snyder wrote:
>>> Add Linux support for the Linear Technology LTC4245 Multiple Supply Hot
>>> Swap controller I2C monitoring interface.
>> (...)
>> That only leaves one issue, it would be nice to be able to map the currents and 
>> voltages together by something other then labels, but allas we have no API in 
>> place for that. We could however try to give them to same numbers.
>>
>> So what I would like to suggest is to have the following sysfs attributes for 
>> inputs:
>>
>> in1_input	12v input  voltage (mV)
>> in2_input	5v  input  voltage (mV)
>> in3_input	3v  input  voltage (mV)
>> curr1_input	12v amperage (mA)
>> curr2_input	12v amperage (mA)
> 
> I guess you mean 5v...
> 
>> curr3_input	12v amperage (mA)
> 
> ... and 3v.
> 

Erm, yes.

>> Given that we measure both output voltage and current, I think it would be cool 
>> to also add power#_input's to the driver, as thats just "output voltage * 
>> current". I know people will start screaming that we should do things like this 
>> in userspace, but given the fact that we have no API to match voltages and 
>> currents, let alone one to do the interesting mapping here, where one current 
>> corresponds to 2 voltages, and given how easy it is to add these 2 this driver, 
>> I'm in favor of adding them, so then we would also get:
>>
>> power1_input 12v power consumption (micro watt)
>> power2_input 5v power consumption (micro watt)
>> power3_input 3v power consumption (micro watt)
>>
>> Jean, whats your 2 cents on this ?
> 
> I don't have enough free time these days to afford having an objection.
> I am not too happy to see non-independent inputs in sysfs, as there's
> no way for the user to know which values are independent and which are
> computer, but indeed we lack a good way to express the relations
> between different inputs. That's the same problem we had for fan# and
> pwm#, or pwm# and temp# for automatic fan speed control. At some point
> it might be convenient to introduce virtual sub-devices grouping
> together things related items. For now, all we have is
> pwm[1-*]_auto_channels_temp to map temperature channels to pwm outputs.
> I guess we could do something similar to link voltage and current
> channels.
> 
> But then again I do not have enough time to properly think about this
> and propose something. So I'd say, do whatever you want, and whoever
> really cares will have to do the thinking and the proposal and update
> the drivers and libsensors if/as needed.

I hear you, but as everyone involved in hwmon seems to be short on time, and as 
  this is the first IC to expose this kind of problems, I think for now its 
best to just stick with what we have. And add the power#_input attributes to 
this driver as a service to userspace, as userspace cannot easily find this out 
itself due to lack of API.

>>> Take it easy on me, this is my first hwmon driver :) I'd love
>>> suggestions for improvements, however.
>> Don't worry, for a first driver it is pretty good :) If you agree with my 
>> proposed sysfs interface and change the driver to match, I think we can get it 
>> in to 2.6.28.
> 
> That's a pretty optimistic statement from someone who isn't in charge ;)

Erm (I get the hint), yes it is :)

Regards,

Hans

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