Re: [PATCH v4 02/13] iio: adc: ad4134: Sign extend sample data

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] build: -Wmaybe-uninitialized warning for conditionally assigned 'sample'
--

commit 6ed41c1a7f4a36c8c7537ebc2c932623b78e2afa
Author: Marcelo Schmitt <marcelo.schmitt@analog.com>

iio: adc: ad4134: Sign extend sample data

Sign extend ADC sample data for correct delivery of negative ADC input
difference.

> diff --git a/drivers/iio/adc/ad4134.c b/drivers/iio/adc/ad4134.c
> index e53c10b9a44a9..6fdeb27d7a42b 100644
> --- a/drivers/iio/adc/ad4134.c
> +++ b/drivers/iio/adc/ad4134.c
> @@ -172,6 +172,7 @@ static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
>  			    unsigned int *val)
>  {
>  	unsigned int i;
> +	u32 sample;
>  	int ret;
>  
>  	/*
> @@ -196,8 +197,9 @@ static int ad4134_data_read(struct ad4134_state *st, unsigned int reg,
>  		 * Clock out data from all channels to avoid that.
>  		 */
>  		if (i == AD4134_VREG_CH(reg))
> -			*val = get_unaligned_be24(st->rx_buf);
> +			sample = get_unaligned_be24(st->rx_buf);
>  	}
> +	*val = sign_extend32(sample, AD4134_CHAN_PRECISION_BITS - 1);
                             ^^^^^^

[Severity: Low]
Does this code trigger a -Wmaybe-uninitialized compiler warning?

The local variable sample is declared without initialization and is only
assigned conditionally if i == AD4134_VREG_CH(reg). While the regmap core
strictly validates reg before invoking the read callback, the compiler analyzes
ad4134_data_read() locally and cannot statically deduce this external bounds
guarantee.

Consequently, the compiler evaluates a theoretical path where the condition is
never met, leaving sample unassigned before it is passed to sign_extend32().

This can cause build failures in kernel configurations with CONFIG_WERROR
enabled. Explicitly initializing u32 sample = 0; or unconditionally performing
the sign extension inside the if block would resolve this.

>  
>  	return 0;
>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/cover.1791309733.git.marcelo.schmitt@analog.com?part=2