linux-kernel - Re: [PATCH v3 26/27] staging: iio: resolver: ad2s1210: implement fault events

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Date:   Mon, 2 Oct 2023 11:43:19 -0500
From:   David Lechner <dlechner@...libre.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        David Lechner <david@...hnology.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Philip Molloy <pmolloy@...libre.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 26/27] staging: iio: resolver: ad2s1210: implement
 fault events

On Sat, Sep 30, 2023 at 11:00 AM Jonathan Cameron <jic23@...nel.org> wrote:
>
> On Fri, 29 Sep 2023 12:23:31 -0500
> David Lechner <dlechner@...libre.com> wrote:
>
> > From: David Lechner <david@...hnology.com>
> >
> > From: David Lechner <dlechner@...libre.com>
> >
> > When reading the position and velocity on the AD2S1210, there is also a
> > 3rd byte following the two data bytes that contains the fault flag bits.
> > This patch adds support for reading this byte and generating events when
> > faults occur.
> >
> > The faults are mapped to various channels and event types in order to
> > have a unique event for each fault.
> >
> > Signed-off-by: David Lechner <dlechner@...libre.com>
>
> Use of x and y modifiers is a little odd.  What was your reasoning?
> Was it just that there was a X_OR_Y modifier?  If so, don't use that!
> It seemed like a good idea at the time, but it's not nice to deal with
> and requires a channel with that modifier to hang the controls off
> + make sure userspace expects that event code.
>

Yes, I was perhaps getting a bit too creative here (the two inputs
come from transformers mounted 90 degrees apart so measure X and Y
component of an angle). The only reason I did this was to take
advantage of the possibility of an "OR" event to avoid double events
for a single fault bit. We can just go with the double event on the
two different input channels as discussed in "[PATCH v3 22/27]
staging: iio: resolver: ad2s1210: convert LOS threshold to event
attr".