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From:   David Lechner <dlechner@baylibre.com>
Date:   Thu, 7 Dec 2023 17:26:02 -0600
Message-ID: <CAMknhBFPbAqp4-AQdmbp+VRW-Ksk1PxaLCG+3n=Zk4gyStqhgw@mail.gmail.com>
Subject: Re: [PATCH v3 00/13] Add support for AD7091R-2/-4/-8
To:     Marcelo Schmitt <marcelo.schmitt@analog.com>
Cc:     apw@canonical.com, joe@perches.com, dwaipayanray1@gmail.com,
        lukas.bulwahn@gmail.com, paul.cercueil@analog.com,
        Michael.Hennerich@analog.com, lars@metafoo.de, jic23@kernel.org,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, dan.carpenter@linaro.org,
        marcelo.schmitt1@gmail.com, linux-iio@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
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On Thu, Dec 7, 2023 at 12:36=E2=80=AFPM Marcelo Schmitt
<marcelo.schmitt@analog.com> wrote:
>
> From: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
>
> ----------------- Updates -----------------
>
> Applied all changes suggested to the previous series.
>
> I tried to better explain the changes but, since there is a fair amount o=
f
> rework in ad7091-base and ad7091r5, it may be hard to get the reasoning f=
or the
> early patches before looking at the patch for ad7091r8.
>
> Change log v2 -> v3:
> - Split alert fix patch into 2 fix patches and one alignment cleanup patc=
h
> - Corrected Fixes tag format
> - Moved MAINTAINERS update to the end of the series
> - Reworded some commit messages to provide context and make their goal cl=
earer
> - Removed erroneous gmail sign off
> - Created container struct to store chip_info, regmap_config, and callbac=
ks
>   specific to each ADC design
> - Created callbacks for chip specific tasks such as setting device operat=
ion mode
> - Dropped the chip type enum struct
> - Applied suggestions related to device tree documentation
> - Added __aligned to list the of checkpatch attribute notes
> - Other code style tidy ups.
>
> I see regmap's interface for reading device registers under /sys/kernel/d=
ebug/regmap/.
> I can read all registers but can't write to any of them unless I force de=
fine
> REGMAP_ALLOW_WRITE_DEBUGFS.
>
> When testing events for this driver I often write to device registers
> to set different rising/falling thresholds. I do something like this:
> # echo 0x17 0x100 > /sys/kernel/debug/iio/iio:device0/direct_reg_access
>
> I tried read/writing to files under iio:device events directory but alway=
s
> get segmentation fault. I must be forgetting to implement something.
> What am I missing?
>

It looks like event callbacks (.read_event_value and friends) are
missing from `static const struct iio_info ad7091r_info =3D { ... }`.
These callbacks aren't checked for NULL, e.g. in iio_ev_value_show(),
so that is likely where the segfault is happening.