Re: [PATCH] iio: dac: ad5446: Fix ad5622_write() return value

From: Alexandru Ardelean <ardeleanalex@gmail.com>
To: Pekka Korpinen <pekka.korpinen@iki.fi>
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	Michael Hennerich <Michael.Hennerich@analog.com>,
	Jonathan Cameron <jic23@kernel.org>,
	linux-iio <linux-iio@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iio: dac: ad5446: Fix ad5622_write() return value
Date: Wed, 29 Sep 2021 12:46:02 +0300	[thread overview]
Message-ID: <CA+U=DspS04Crdr7OwfrTuBueTYOA+rV9sS0_mB-Q9+hsoufxKw@mail.gmail.com> (raw)
In-Reply-To: <20210928195548.17846-1-pekka.korpinen@iki.fi>

On Tue, Sep 28, 2021 at 10:57 PM Pekka Korpinen <pekka.korpinen@iki.fi> wrote:
>
> 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.
>

Requires a Fixes tag.
But other than that:

Reviewed-by: Alexandru Ardelean <ardeleanalex@gmail.com>

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