linux-kernel - Re: [Letux-kernel] [PATCH 0/4] mfd: rn5t618: Extend ADC support

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Date:   Sun, 4 Jul 2021 17:10:23 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     Discussions about the Letux Kernel <letux-kernel@...nphoenux.org>,
        devicetree@...r.kernel.org, lars@...afoo.de,
        linux-pm@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, sre@...nel.org, robh+dt@...nel.org,
        leonard.crestez@....com, lee.jones@...aro.org
Subject: Re: [Letux-kernel] [PATCH 0/4] mfd: rn5t618: Extend ADC support

On Sat, 3 Jul 2021 18:55:40 +0200
Andreas Kemnade <andreas@...nade.info> wrote:

> On Sat, 3 Jul 2021 18:39:40 +0200
> Andreas Kemnade <andreas@...nade.info> wrote:
> 
> > Hi,
> > 
> > On Sat, 3 Jul 2021 16:59:50 +0100
> > Jonathan Cameron <jic23@...nel.org> wrote:
> >   
> > > On Sat,  3 Jul 2021 10:42:20 +0200
> > > Andreas Kemnade <andreas@...nade.info> wrote:
> > >     
> > > > Add devicetree support so that consumers can reference the channels
> > > > via devicetree, especially the power subdevice can make use of that
> > > > to provide voltage_now properties.      
> > > 
> > > Does the mapping vary from board to board?  Often these mappings are
> > > internal to the chip so might as well be provided hard coded in the
> > > relevant drivers rather than via DT. See drivers that have iio_map
> > > structure arrays.
> > >     
> > Most things are internal to the chip, but 
> > AIN1/AIN0 are external and could be connected to anything.
> >   
> hmm, iio_map stuff looks nice, so before messing with devicetree,
> I could solve 90% of the problem by just using iio_map? For my use
> cases it is enough to have the internal stuff at the moment. That would
> simplify stuff a lot.
> 
> So I could go forward with the iio_map stuff now, and if there is a use
> case for AIN1/0, the devicetree stuff can be added later?

I was just thinking the same.  I 'think' that it will first try to find
a mapping via device tree and then use the iio_map stuff.

So you can probably get away with a mixture of the two.
Worth testing that works though (hook up iio-hwmon to AIN0 perhaps whilst
also using the iio_map approach).

I might be completely wrong though and am not aware of anyone currently
doing this...

Jonathan

> 
> Regards,
> Andreas