linux-kernel - [PATCH] iio: dac: ad5446: Fix ad5622

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Date:   Tue, 28 Sep 2021 22:55:48 +0300
From:   Pekka Korpinen <pekka.korpinen@....fi>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Pekka Korpinen <pekka.korpinen@....fi>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] iio: dac: ad5446: Fix ad5622_write() return value

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.

Signed-off-by: Pekka Korpinen <pekka.korpinen@....fi>
---
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.

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

 drivers/iio/dac/ad5446.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/dac/ad5446.c b/drivers/iio/dac/ad5446.c
index 488ec69967d6..dfd541bbde5b 100644
--- a/drivers/iio/dac/ad5446.c
+++ b/drivers/iio/dac/ad5446.c
@@ -531,8 +531,13 @@ 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;
 
-	return i2c_master_send(client, (char *)&data, sizeof(data));
+	return 0;
 }
 
 /*
-- 
2.33.0