linux-kernel - Re: [PATCH v2 5/5] iio:humidity:hts221: rearrange iio trigger get and register

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Date:   Tue, 24 May 2022 21:52:02 +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 5/5] iio:humidity:hts221: 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: e4a70e3e7d84 ("iio: humidity: add support to hts221 rh/temp combo device")
> Signed-off-by: Dmitry Rokosov <ddrokosov@...rdevices.ru>
> ---
>  drivers/iio/humidity/hts221_buffer.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/humidity/hts221_buffer.c b/drivers/iio/humidity/hts221_buffer.c
> index f29692b9d2db..66b32413cf5e 100644
> --- a/drivers/iio/humidity/hts221_buffer.c
> +++ b/drivers/iio/humidity/hts221_buffer.c
> @@ -135,9 +135,12 @@ int hts221_allocate_trigger(struct iio_dev *iio_dev)
>
>         iio_trigger_set_drvdata(hw->trig, iio_dev);
>         hw->trig->ops = &hts221_trigger_ops;
> +
> +       err = devm_iio_trigger_register(hw->dev, hw->trig);
> +
>         iio_dev->trig = iio_trigger_get(hw->trig);
>
> -       return devm_iio_trigger_register(hw->dev, hw->trig);
> +       return err;
>  }
>
>  static int hts221_buffer_preenable(struct iio_dev *iio_dev)
> --
> 2.36.0



-- 
With Best Regards,
Andy Shevchenko