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From:   Andrea Merello <Andrea.Merello@iit.it>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
CC:     Jonathan Cameron <jic23@kernel.org>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        "Rob Herring" <robh+dt@kernel.org>,
        Matt Ranostay <matt.ranostay@konsulko.com>,
        Alexandru Ardelean <ardeleanalex@gmail.com>,
        jmondi <jacopo@jmondi.org>,
        "andrea.merello@gmail.com" <andrea.merello@gmail.com>
Subject: Re: [v6 08/14] iio: imu: add Bosch Sensortec BNO055 core driver
Thread-Topic: [v6 08/14] iio: imu: add Bosch Sensortec BNO055 core driver
Thread-Index: AQHYfx3utmV3pJ3K2U+b/YbA0CL4iq1NadiAgAExt3mAAAAAgIAAMcuB
Date:   Tue, 14 Jun 2022 12:15:09 +0000
Message-ID: <a41936e4063f4c2c9da7c7e1d915bd62@iit.it>
References: <20220613120534.36991-1-andrea.merello@iit.it>
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    >
> ...
>
>> >> +static void bno055_debugfs_init(struct iio_dev *iio_dev)
>> >> +{
>> >> +       struct bno055_priv *priv =3D iio_priv(iio_dev);
>> >> +
>> >> +       priv->debugfs =3D debugfs_create_file("firmware_version", 040=
0,
>> >> +                                           iio_get_debugfs_dentry(ii=
o_dev),
>> >> +                                           priv, &bno055_fw_version_=
ops);
>> >
>> >> +       devm_add_action_or_reset(priv->dev, bno055_debugfs_remove, pr=
iv->debugfs);
>> >
>> >Shouldn't we report the potential error here? It's not directly
>> >related to debugfs, but something which is not directly related.
>>
>> The error eventually comes out from something that has nothing to do wit=
h debugs per se (i.e. the devm stuff), but it will only affect debugfs inde=
ed.
>>
>> Assuming that we don't want to make the whole driver fail in case debugf=
s stuff fails (see last part of the comment above debugfs_create_file() imp=
lementation), and given that the devm_add_action_or_reset(), should indeed =
"reset" in case of failure (i.e.  we should be in a clean situation anyway)=
, I would say it should be OK not to propagate the error and let things go =
on.
>
>As I said, it's not directly related to debugfs. Here is the resource
>leak possible or bad things happen if you probe the driver, that fails
>to add this call for removal, remove it, and try to insert again, in
>such case the debugfs will be stale.

Hum, I would say this shouldn't ever happen: AFAICS devm_add_action_or_rese=
t() is a wrapper around devm_add_action() and it's purpose is exactly to ad=
d a check for failure; devm_add_action_or_reset() immediately invokes the a=
ction handler in case devm_add_action() fails. IOW in case of failure to ad=
d the devm stuff, the debugfs file is removed immediately and it shouldn't =
cause any mess with next times probe()s; just the driver will go on without=
 the debugfs file being here.

I think this is the point of using devm_add_action_or_reset() instead of de=
v_add_action()  indeed, or am I missing something?

>> However we can add a dev_warn() to report what happened.
>
>Not sure if it would suffice, I leave it to Jonathan.
>
>--=20
>With Best Regards,
>Andy Shevchenko=