Re: ABI for these two registers?

[Nicolin Chen <nicoleotsuka@gmail.com>]

Hello Guenter,

It's been nearly three weeks. Would it be possible for you to
provide some advice on my latest questions? I'd like to write
code and submit changes once ABI is confirmed...

Thank you!

On Thu, Sep 12, 2019 at 05:12:38PM -0700, Nicolin Chen wrote:

> > > > > > Datasheet: http://www.ti.com/lit/ds/symlink/ina3221.pdf
> > > > > > (At page 32, chapter 8.6.2.14 and 8.6.2.15)
> > > > > > 
> > > > > > I have two registers that I need to expose to user space:
> > > > > > 	Shunt-Voltage-Sum and Shunt-Voltage-Limit registers
> > > > > > 
> > > > > > Right now in[123]_input of INA3221 are for voltage channels
> > > > > > while in[456]_input are for Shunt voltage channels.
> > > > > > 
> > > > > > So can I just use in7_input and in7_crit for them?
> > > > > > 
> > > > > Doesn't Shunt-Voltage-Limit apply to in[456]_input ?
> > > > > If so, the limit should be attached to those.
> > > > 
> > > > The initial patch of ina3221 driver applied Shunt-Voltage-Limits,
> > > > being named as "Critical Alert Limit Registers" in the datasheet,
> > > > to curr[123]_crit, corresponding to curr[123] and in[456]_input.
> > > > 
> > > > And this Shunt-Voltage-Limit-Sum is more related to the reading
> > > > from Shunt-Voltage-Sum, which we just agreed it to be in7_input.
> > > > 
> > > You didn't say Shunt-Voltage-Limit-Sum earlier. You said
> > 
> > Ah....right...it's my fault. Sorry.
> > 
> > > Shunt-Voltage-Limit. I would agree that Shunt-Voltage-Limit-Sum is
> > > associated with Shunt-Voltage-Sum, but, again, that is not what you
> > > said earlier. Confused :-(
> > 
> > So, those two should be in7_input and in7_crit?
> 
> And a couple of more questions upon it:
> 
> 1) There are 3 control bits for the summation of this
>    shunt-voltage-sum register to enable corresponding
>    input channels. But in7_enable only allows users to
>    en/disable all three channels at the same time. So
>    how should I attach three enable bits using ABI?
>    Or should I create a device-specific sysfs node?
> 
> 2) We have a requirement of providing current-sum and
>    current-limit-sum nodes, for use cases where those
>    enabled channels use same value shunt resistors.
>    It's similar to provide curr[1-3]_crit by dividing
>    shunt[123]_resistor from in[456]_input. So could I
>    deploy curr4_input and curr4_crit nodes for this
>    requirement?