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From: Pekka Korpinen <pekka.korpinen@iki.fi>
To: unlisted-recipients:; (no To-header on input)
Cc: ardeleanalex@gmail.com, Pekka Korpinen <pekka.korpinen@iki.fi>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Michael Hennerich <Michael.Hennerich@analog.com>,
	Jonathan Cameron <jic23@kernel.org>,
	Jean-Francois Dagenais <jeff.dagenais@gmail.com>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] iio: dac: ad5446: Fix ad5622_write() return value
Date: Wed, 29 Sep 2021 21:57:55 +0300	[thread overview]
Message-ID: <20210929185755.2384-1-pekka.korpinen@iki.fi> (raw)
In-Reply-To: <20d11fbb-ba93-802c-1abc-60d7f5ec0c0c@metafoo.de>

On success i2c_master_send() returns the number of bytes written. The
call from iio_write_channel_info(), however, expects the return value to
be zero on success.

This bug causes incorrect consumption of the sysfs buffer in
iio_write_channel_info(). When writing more than two characters to
out_voltage0_raw, the ad5446 write handler is called multiple times
causing unexpected behavior.

Fixes: 3ec36a2cf0d5 ("iio:ad5446: Add support for I2C based DACs")
Signed-off-by: Pekka Korpinen <pekka.korpinen@iki.fi>
---
v1->v2: Check against expected result, otherwise -EIO. Add Fixes tag.

A similar bug was fixed for ad5064.c in 2015 - commit 03fe472ef33b
("iio:ad5064: Make sure ad5064_i2c_write() returns 0 on success").

 drivers/iio/dac/ad5446.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/dac/ad5446.c b/drivers/iio/dac/ad5446.c
index 488ec69967d6..e50718422411 100644
--- a/drivers/iio/dac/ad5446.c
+++ b/drivers/iio/dac/ad5446.c
@@ -531,8 +531,15 @@ static int ad5622_write(struct ad5446_state *st, unsigned val)
 {
 	struct i2c_client *client = to_i2c_client(st->dev);
 	__be16 data = cpu_to_be16(val);
+	int ret;
+
+	ret = i2c_master_send(client, (char *)&data, sizeof(data));
+	if (ret < 0)
+		return ret;
+	if (ret != sizeof(data))
+		return -EIO;
 
-	return i2c_master_send(client, (char *)&data, sizeof(data));
+	return 0;
 }
 
 /*
-- 
2.33.0


  reply	other threads:[~2021-09-29 18:58 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-28 19:55 [PATCH] " Pekka Korpinen
2021-09-29  9:46 ` Alexandru Ardelean
2021-09-29  9:59 ` Lars-Peter Clausen
2021-09-29 18:57   ` Pekka Korpinen [this message]
2021-10-17 10:43     ` [PATCH v2] " Jonathan Cameron

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