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

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Message-ID: <20230311123547.66adc751@jic23-huawei>
Date:   Sat, 11 Mar 2023 12:35:47 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     lars@...afoo.de, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] iio: dac: cio-dac: Fix max DAC write value check for
 12-bit

On Fri, 10 Mar 2023 19:22:48 -0500
William Breathitt Gray <william.gray@...aro.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@...r.kernel.org
> Signed-off-by: William Breathitt Gray <william.gray@...aro.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