linux-kernel - [PATCH v1 5/5] iio:humidity:hts221: rearrange iio trigger get and register

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Date:   Mon, 23 May 2022 18:36:30 +0000
From:   Dmitry Rokosov <DDRokosov@...rdevices.ru>
To:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "lars@...afoo.de" <lars@...afoo.de>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "lorenzo.bianconi83@...il.com" <lorenzo.bianconi83@...il.com>
CC:     "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        kernel <kernel@...rdevices.ru>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dmitry Rokosov <DDRokosov@...rdevices.ru>
Subject: [PATCH v1 5/5] iio:humidity:hts221: rearrange iio trigger get and
 register

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
callbacks or rmmod) will derefence "default" module refcnt, which is
completely incorrect.

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