Re: [PATCH v3 22/27] staging: iio: resolver: ad2s1210: convert LOS threshold to event attr

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 4 Oct 2023 11:01:56 +0000
"Hennerich, Michael" <Michael.Hennerich@analog.com> wrote:

> > -----Original Message-----
> > From: Jonathan Cameron <jic23@kernel.org>
> > Sent: Samstag, 30. September 2023 17:32
> > To: David Lechner <dlechner@baylibre.com>
> > Cc: linux-iio@vger.kernel.org; devicetree@vger.kernel.org; linux-
> > staging@lists.linux.dev; David Lechner <david@lechnology.com>; Rob Herring
> > <robh+dt@kernel.org>; Krzysztof Kozlowski
> > <krzysztof.kozlowski+dt@linaro.org>; Conor Dooley <conor+dt@kernel.org>;
> > Hennerich, Michael <Michael.Hennerich@analog.com>; Sa, Nuno
> > <Nuno.Sa@analog.com>; Axel Haslam <ahaslam@baylibre.com>; Philip Molloy
> > <pmolloy@baylibre.com>; linux-kernel@vger.kernel.org
> > Subject: Re: [PATCH v3 22/27] staging: iio: resolver: ad2s1210: convert LOS
> > threshold to event attr
> > 
> > 
> > On Fri, 29 Sep 2023 12:23:27 -0500
> > David Lechner <dlechner@baylibre.com> wrote:
> >   
> > > From: David Lechner <david@lechnology.com>
> > >
> > > From: David Lechner <dlechner@baylibre.com>
> > >
> > > The AD2S1210 has a programmable threshold for the loss of signal (LOS)
> > > fault. This fault is triggered when either the sine or cosine input
> > > falls below the threshold voltage.
> > >
> > > This patch converts the custom device LOS threshold attribute to an
> > > event falling edge threshold attribute on a new monitor signal channel.
> > > The monitor signal is an internal signal that combines the amplitudes
> > > of the sine and cosine inputs as well as the current angle and
> > > position output. This signal is used to detect faults in the input signals.
> > >
> > > The attribute now uses millivolts instead of the raw register value in
> > > accordance with the IIO ABI.
> > >
> > > Emitting the event will be implemented in a later patch.
> > >
> > > Signed-off-by: David Lechner <dlechner@baylibre.com>  
> > 
> > I think I'm fine with treating these internal signals like this, but I would ideally
> > like someone from Analog devices to take a look at how these are being done
> > and make sure our interpretations of the signals make sense to them.  We are
> > pushing the boundaries a little here (though we have done similar before for
> > fault events I think.)  
> 
> Hi Jonathan,
> David and I we also had some internal discussion related to this.
> I'm sure these fault events and thresholds are understood correctly.
> Doing it this or the other way, it needs to be properly documented in order to make sense.
> So from my perspective whatever makes the most sense from a IIO ABI
> perspective, is the way to forward.

Great - as long as keep to a logical mapping I quite like the events
approach.  Most of these faults are real thresholds on things being measured
(even if those 'things' are signals from which stuff is derived for the main
measurements the device is making.)

Jonathan

> 
> -Michael
> 
> > 
> > Jonathan  
>