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

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

[Pekka Korpinen]

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@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

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

[Alexandru Ardelean]

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
>

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

[Lars-Peter Clausen]

On 9/28/21 9:55 PM, Pekka Korpinen 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.
>
> 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.

I'd put this into the commit message itself. This is useful information 
that should be part of the commit log.

>
> 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;
Like you wrote in the commit message the function returns the number of 
bytes written. We should check that this matches the number of bytes we 
wanted to send and return an error (EIO) otherwise.
>   
> -	return i2c_master_send(client, (char *)&data, sizeof(data));
> +	return 0;
>   }
>   
>   /*

[PATCH v2] iio: dac: ad5446: Fix ad5622_write() return value

[Pekka Korpinen]

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

Re: [PATCH v2] iio: dac: ad5446: Fix ad5622_write() return value

[Jonathan Cameron]

On Wed, 29 Sep 2021 21:57:55 +0300
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.
> 
> 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>
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan

> ---
> 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;
>  }
>  
>  /*