linux-kernel - Re: [PATCH v2 3/5] iio:accel:mxc4005: rearrange iio trigger get and register

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Date:   Tue, 24 May 2022 21:50:49 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Dmitry Rokosov <DDRokosov@...rdevices.ru>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "lorenzo.bianconi83@...il.com" <lorenzo.bianconi83@...il.com>,
        "srinivas.pandruvada@...ux.intel.com" 
        <srinivas.pandruvada@...ux.intel.com>,
        "teodora.baluta@...el.com" <teodora.baluta@...el.com>,
        "narcisaanamaria12@...il.com" <narcisaanamaria12@...il.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] iio:accel:mxc4005: rearrange iio trigger get and register

On Tue, May 24, 2022 at 8:14 PM Dmitry Rokosov <DDRokosov@...rdevices.ru> wrote:
>
> IIO trigger interface function iio_trigger_get() should be called after
> iio_trigger_register() (or its devm analogue) strictly, because of
> iio_trigger_get() acquires module refcnt based on the trigger->owner
> pointer, which is initialized inside iio_trigger_register() to
> THIS_MODULE.
> If this call order is wrong, the next iio_trigger_put() (from sysfs
> callback or "delete module" path) will dereference "default" module
> refcnt, which is incorrect behaviour.

Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Fixes: 47196620c82f ("iio: mxc4005: add data ready trigger for mxc4005")
> Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
> ---
>  drivers/iio/accel/mxc4005.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/accel/mxc4005.c b/drivers/iio/accel/mxc4005.c
> index b3afbf064915..df600d2917c0 100644
> --- a/drivers/iio/accel/mxc4005.c
> +++ b/drivers/iio/accel/mxc4005.c
> @@ -456,8 +456,6 @@ static int mxc4005_probe(struct i2c_client *client,
>
>                 data->dready_trig->ops = &mxc4005_trigger_ops;
>                 iio_trigger_set_drvdata(data->dready_trig, indio_dev);
> -               indio_dev->trig = data->dready_trig;
> -               iio_trigger_get(indio_dev->trig);
>                 ret = devm_iio_trigger_register(&client->dev,
>                                                 data->dready_trig);
>                 if (ret) {
> @@ -465,6 +463,8 @@ static int mxc4005_probe(struct i2c_client *client,
>                                 "failed to register trigger\n");
>                         return ret;
>                 }
> +
> +               indio_dev->trig = iio_trigger_get(data->dready_trig);
>         }
>
>         return devm_iio_device_register(&client->dev, indio_dev);
> --
> 2.36.0



-- 
With Best Regards,
Andy Shevchenko