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Message-ID: <380ae3c3-14c2-db1a-954c-caf8180746f0@vixtechnology.com>
Date:   Fri, 11 Nov 2022 21:44:48 +0800
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Subject: Re: [PATCH] iio: light: apds9960: Fix iio_event_spec structures
To:     Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
        Matt Ranostay <matt.ranostay@konsulko.com>
Cc:     jic23@kernel.org, lars@metafoo.de, linux-kernel@vger.kernel.org,
        linux-iio@vger.kernel.org
References: <20221110101241.10576-1-subhajit.ghosh@vixtechnology.com>
 <CAJCx=g=qRd+WaCLOHwnEjg1Myg4Ng=PK0sxcGgEG9VT+VpondA@mail.gmail.com>
 <b6ac2692-3152-dfc4-5388-7986042970f0@vixtechnology.com>
 <CAJCx=g=WaGiBFYJTTjNgzrnW3We0qpuMvyy9iFAVDC8Mkbscsg@mail.gmail.com>
 <20221111111049.0000467f@Huawei.com>
From:   Subhajit Ghosh <subhajit.ghosh@vixtechnology.com>
In-Reply-To: <20221111111049.0000467f@Huawei.com>
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> Hmm.  Given that event enables often cover a couple of different things
> (as done here) it isn't unknown for those to not be as easily covered
> as you have done.  As such, we have drivers were the ABI allows for
> enabling one event to end up enabling several others (even though they
> have separate enable attributes).  It's always been permitted for one
> IIO attribute write to have an effect on other attributes simply because
> we can't represent all dependencies.
>=20
> Now the bigger complexity / surprise here is the return of the either
> direction in response to enabling either rising or falling.=20
> That is going to rather surprise your average writer of userspace cod Thi=
s is where the inconsistency was found. When an ALS threshold rising=20
value was given and as soon as it was enabled, interrupts started firing
in low light conditions as there was some value present in the ALS falling=
=20
threshold(reset value is not defined in the datasheet for this register),=
=20
but falling threshold value was neither fed nor enabled!

> So patch covers what we should definitely have had in the first place.
> Hence it's a question of risk of someone running code that will be affect=
ed
> by the ABI change.  One of those fingers crossed moments...
I understand that breaking existing userspace applications is not the best
thing to do.

>=20
> Jonathan

Thank you for your time and comments.

Regards,
Subhajit Ghosh

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