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From:   David Lechner <dlechner@baylibre.com>
Date:   Mon, 2 Oct 2023 13:49:51 -0500
Message-ID: <CAMknhBGFpYx3oYqJgVgKZpoeANmVmXtUn+V3VnAW7woc7ytTow@mail.gmail.com>
Subject: Re: [PATCH v3 26/27] staging: iio: resolver: ad2s1210: implement
 fault events
To:     Jonathan Cameron <jic23@kernel.org>
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>,
        Michael Hennerich <Michael.Hennerich@analog.com>,
        =?UTF-8?B?TnVubyBTw6E=?= <nuno.sa@analog.com>,
        Axel Haslam <ahaslam@baylibre.com>,
        Philip Molloy <pmolloy@baylibre.com>,
        linux-kernel@vger.kernel.org
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On Mon, Oct 2, 2023 at 11:58=E2=80=AFAM David Lechner <dlechner@baylibre.co=
m> wrote:
>
> On Sat, Sep 30, 2023 at 11:00=E2=80=AFAM Jonathan Cameron <jic23@kernel.o=
rg> wrote:
> >
> > On Fri, 29 Sep 2023 12:23:31 -0500
> > David Lechner <dlechner@baylibre.com> wrote:
> >
> > > From: David Lechner <david@lechnology.com>
> > >
> > > From: David Lechner <dlechner@baylibre.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 bi=
ts.
> > > This patch adds support for reading this byte and generating events w=
hen
> > > 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@baylibre.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.
>
>
> Regarding the point about "requires a channel with that modifier to
> hang the controls off...". Although that comment was about modifiers,
> does it also apply in general.
>
> There are several fault events that don't have any configurable
> parameters, namely _sine/cosine inputs clipping_ and _velocity exceeds
> max tracking rate_. So there won't be any attributes that contain the
> event specification for those (e.g. no `events/in_angl0_*`
> attributes). It sounds like this would be a problem as well?
>
> Should we consider a IIO_EV_INFO_LABEL so that we can have some sort
> of attribute (namely `events/<dir>_<channel spec>_label`) so that
> userspace can enumerate expected events for non-configurable events?

Well, I didn't think that all the way through before I hit send.
IIO_EV_INFO_LABEL is clearly not the right way to implement a
`events/*_label` attribute, but however we consider going about it,
the point of adding such an attribute was the main idea.