Re: [PATCH] iio: dac: mcp47feb02: Fix mutex used before initialization

[Nuno Sá]

On Mon, 2026-02-23 at 16:03 +0800, Felix Gu wrote:
> The mcp47feb02_parse_fw() function uses data->lock, but the mutex was
> initialized after this function in probe path.
> 
> Fix this by moving devm_mutex_init() before mcp47feb02_parse_fw().
> 
> Fixes: bf394cc80369 ("iio: dac: adding support for Microchip MCP47FEB02")
> Signed-off-by: Felix Gu <ustc.gu@xxxxxxxxx>
> ---
>  drivers/iio/dac/mcp47feb02.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/dac/mcp47feb02.c b/drivers/iio/dac/mcp47feb02.c
> index b218f0c3a0bd..4ff5abcfecea 100644
> --- a/drivers/iio/dac/mcp47feb02.c
> +++ b/drivers/iio/dac/mcp47feb02.c
> @@ -1131,14 +1131,14 @@ static int mcp47feb02_probe(struct i2c_client *client)
>  
>  	indio_dev->name = chip_features->name;
>  
> -	ret = mcp47feb02_parse_fw(indio_dev, chip_features);
> -	if (ret)
> -		return dev_err_probe(dev, ret, "Error parsing firmware data\n");
> -
>  	ret = devm_mutex_init(dev, &data->lock);
>  	if (ret)
>  		return ret;
>  
> +	ret = mcp47feb02_parse_fw(indio_dev, chip_features);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Error parsing firmware data\n");
> +

Actually I think the better fix is to not lock at all? Why do we need a lock around 
mcp47feb02_parse_fw() if it's only called from probe()?

- Nuno Sá
>