Re: [PATCH 0/4] IIO wrapper drivers, dpot-dac and envelope-detector

[jic23]

On 20.10.2016 19:17, Peter Rosin wrote:
> On 2016-10-20 19:37, Jonathan Cameron wrote:
> > On 20 October 2016 18:30:19 BST, Jonathan Cameron 
> > <jic23@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > > On 20 October 2016 13:55:12 BST, Lars-Peter Clausen <lars@xxxxxxxxxx> 
> > > wrote:
> > > > On 10/20/2016 11:25 AM, Peter Rosin wrote:
> > > > > Also, is there some agreed-upon way to dig out the maximum value 
> > > > > from
> > > > > an iio channel? If so, "dpot-dac,max-ohms" can be eliminated from 
> > > > > the
> > > > > dt bindings, which would have been nice...
> > > >
> > > > Yes, this is something we could really use. In a sense it exists for
> > > > the
> > > > devices with buffer-capable channels where there is the real_bits 
> > > > field
> > > > which tells us the data width of the channel. But a dedicated 
> > > > mechanism
> > > > for
> > > > querying the maximum (and minimum) valid code seems like a useful
> > > > feature.
> > > > Not only for in-kernel clients, but also for userspace.
> > >
> > > This was something that was addressed by the rather ancient patch
> > > series i posted that added
> > > an available call back which provided info on range and values for 
> > > all
> > > info mask elements.
> > > Series got buried by there being a lot of precursors but quite a few 
> > > of
> > > those have merged since.
> > >
> > > Hmm Google won't let me find it on my phone. Was a while back now. 
> > > Will
> > > try to get on pc with
> > > decent email archive later and dig out a reference.
> > http://marc.info/?l=linux-iio&m=138469765309868&w=2 I think...
>
> Interesting, one issue with that is that it is all in real world
> units, while I'd rather have the raw value.
Um.. It's been a while, but the principle was (IIRC) that every
_available would match the units fo the associated info mask element.
Thus if you have a _raw element it would be in adc counts (most likely).

_input would be in relevant real world units, scale etc in the whatever
units the value itself is in.

> So, I would need to
> convert back to the raw value using the scale, which sounds boring
> but doable. However, I wonder if calibration may also be involved
> with that conversion back to raw for some channels? That sounds a
> bit more driver specific and potentially troublesome...
I've not had a chance to look at your code (only picked up on this as
there was a fair length thread developing), but I wouldn't have thought 
we'd
need to deal with calibrations.   Might need them to move to real world
units from raw but that's always the case anyway (unfortunately).

Jonathan
> Cheers,
> Peter
>
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