[PATCH] iio: dac: cio-dac: Fix max DAC write value check for 12-bit

[PATCH] iio: dac: cio-dac: Fix max DAC write value check for 12-bit

[William Breathitt Gray]

The CIO-DAC series of devices only supports DAC values up to 12-bit
rather than 16-bit. Trying to write a 16-bit value results in only the
lower 12 bits affecting the DAC output which is not what the user
expects. Instead, adjust the DAC write value check to reject values
larger than 12-bit so that they fail explicitly as invalid for the user.

Fixes: 3b8df5fd526e ("iio: Add IIO support for the Measurement Computing CIO-DAC family")
Cc: stable@vger.kernel.org
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
---
 drivers/iio/dac/cio-dac.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/dac/cio-dac.c b/drivers/iio/dac/cio-dac.c
index 791dd999cf29..18a64f72fc18 100644
--- a/drivers/iio/dac/cio-dac.c
+++ b/drivers/iio/dac/cio-dac.c
@@ -66,8 +66,8 @@ static int cio_dac_write_raw(struct iio_dev *indio_dev,
 	if (mask != IIO_CHAN_INFO_RAW)
 		return -EINVAL;
 
-	/* DAC can only accept up to a 16-bit value */
-	if ((unsigned int)val > 65535)
+	/* DAC can only accept up to a 12-bit value */
+	if ((unsigned int)val > 4095)
 		return -EINVAL;
 
 	priv->chan_out_states[chan->channel] = val;

base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
-- 
2.39.2

Re: [PATCH] iio: dac: cio-dac: Fix max DAC write value check for 12-bit

[Jonathan Cameron]

On Fri, 10 Mar 2023 19:22:48 -0500
William Breathitt Gray <william.gray@linaro.org> wrote:

> The CIO-DAC series of devices only supports DAC values up to 12-bit
> rather than 16-bit. Trying to write a 16-bit value results in only the
> lower 12 bits affecting the DAC output which is not what the user
> expects. Instead, adjust the DAC write value check to reject values
> larger than 12-bit so that they fail explicitly as invalid for the user.
> 
> Fixes: 3b8df5fd526e ("iio: Add IIO support for the Measurement Computing CIO-DAC family")
> Cc: stable@vger.kernel.org
> Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Applied to the fixes-togreg branch of iio.git.

Thanks,

Jonathan

> ---
>  drivers/iio/dac/cio-dac.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/dac/cio-dac.c b/drivers/iio/dac/cio-dac.c
> index 791dd999cf29..18a64f72fc18 100644
> --- a/drivers/iio/dac/cio-dac.c
> +++ b/drivers/iio/dac/cio-dac.c
> @@ -66,8 +66,8 @@ static int cio_dac_write_raw(struct iio_dev *indio_dev,
>  	if (mask != IIO_CHAN_INFO_RAW)
>  		return -EINVAL;
>  
> -	/* DAC can only accept up to a 16-bit value */
> -	if ((unsigned int)val > 65535)
> +	/* DAC can only accept up to a 12-bit value */
> +	if ((unsigned int)val > 4095)
>  		return -EINVAL;
>  
>  	priv->chan_out_states[chan->channel] = val;
> 
> base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6