Re: [PATCH] iio: dac: Fix passing uninitialized vref1_uV for no Vref1 case

[David Lechner <dlechner@baylibre.com>]

On 4/14/26 7:33 AM, Ariana Lazar wrote:
> Initialize vref1_uV variable to 0 before calling
> mcp47feb02_init_ch_scales() in mcp47feb02_probe() to avoid passing an
> uninitialized value when have_ext_vref1 is false.
> 
> Fixes: dd154646d292 ("iio: dac: mcp47feb02: Fix Vref validation [1-999] case")
> Reported-by: Dan Carpenter <error27@gmail.com>
> Closes: https://lore.kernel.org/all/adiPnla0M5EzvgD-@stanley.mountain/
> Signed-off-by: Ariana Lazar <ariana.lazar@microchip.com>
> ---
>  drivers/iio/dac/mcp47feb02.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/dac/mcp47feb02.c b/drivers/iio/dac/mcp47feb02.c
> index faccb804a5ed548088aaf83266b16ed45a92916c..efd4847913e46a4fa1b671aa9c5bd3e1430406b7 100644
> --- a/drivers/iio/dac/mcp47feb02.c
> +++ b/drivers/iio/dac/mcp47feb02.c
> @@ -1095,9 +1095,10 @@ static int mcp47feb02_probe(struct i2c_client *client)
>  {
>  	const struct mcp47feb02_features *chip_features;
>  	struct device *dev = &client->dev;
> +	int vdd_uV, vref_uV, vref1_uV;
>  	struct mcp47feb02_data *data;
>  	struct iio_dev *indio_dev;
> -	int vref1_uV, vref_uV, vdd_uV, ret;
> +	int ret;
>  
>  	indio_dev = devm_iio_device_alloc(dev, sizeof(*data));
>  	if (!indio_dev)
> @@ -1146,13 +1147,13 @@ static int mcp47feb02_probe(struct i2c_client *client)
>  		dev_dbg(dev, "Vref is unavailable.\n");
>  	}
>  
> +	vref1_uV = 0;
>  	if (chip_features->have_ext_vref1) {
>  		ret = devm_regulator_get_enable_read_voltage(dev, "vref1");

I don't think ignoring all errors here is a good idea. For example, what
if it returned -EPROBE_DEFER? Then we could end up with the wrong reference
voltage instead of trying again later.

So probably something like this would be better (also fixes uninitialized
variable):

	if (chip_features->have_ext_vref1 &&
	    device_property_present(dev, "vref1")) {
		ret = devm_regulator_get_enable_read_voltage(dev, "vref1");
		if (ret < 0)
			return ret;

		vref1_uV = ret;
		data->use_vref1 = true;
	} else {
		vref1_uV = 0;
		dev_dbg(dev, "using internal band gap as voltage reference 1.\n");
	}


>  		if (ret > 0) {
>  			vref1_uV = ret;
>  			data->use_vref1 = true;
>  		} else {
> -			vref1_uV = 0;
>  			dev_dbg(dev, "using internal band gap as voltage reference 1.\n");
>  			dev_dbg(dev, "Vref1 is unavailable.\n");
>  		}
> 
> ---
> base-commit: 51e7665ab81f02adc80a1219c260ee678e9c6eb8
> change-id: 20260414-mcp47feb02-fix4-614de9334f22
> 
> Best regards,