iio: dac: ad5446: Fix ad5622_write() return value

BugLink: https://bugs.launchpad.net/bugs/1951822
commit 558df982d4ead9cac628153d0d7b60feae05ddc8 upstream.

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>
Link: https://lore.kernel.org/r/20210929185755.2384-1-pekka.korpinen@iki.fi
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/iio/dac/ad5446.c b/drivers/iio/dac/ad5446.c
index 488ec69967d671f842d6e89591a69508ac806064..e50718422411dcb81eb64f9f02b0ae8c9b29fc6b 100644 (file)
--- 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;
 }
 
 /*