Re: [PATCH 2/2] iio: adc: ad7173: Fix comparison of channel configs

[Andy Shevchenko <andy@kernel.org>]

On Thu, Jan 30, 2025 at 06:45:02PM +0100, Uwe Kleine-König wrote:
> Checking the binary representation of two structs (of the same type)
> for equality doesn't have the same semantic as comparing all members for
> equality. The former might find a difference where the latter doesn't in
> the presence of padding or when ambiguous types like float or bool are
> involved. (Floats typically have different representations for single
> values, like -0.0 vs +0.0, or 0.5 * 2² vs 0.25 * 2³. The type bool has
> at least 8 bits and the raw values 1 and 2 (probably) both evaluate to
> true, but memcmp finds a difference.)

memcmp()

> When searching for a channel that already has the configuration we need,
> the comparison by member is the one that is needed.
> 
> Convert the comparison accordingly to compare the members one after
> another. Also add a BUILD_BUG guard to (somewhat) ensure that when

static_assert() will give a better messaging.

> struct ad7173_channel_config::config_props is expanded, the comparison
> is adapted, too.

-- 
With Best Regards,
Andy Shevchenko