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.)
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
struct ad7173_channel_config::config_props is expanded, the comparison
is adapted, too.
Fixes: 76a1e6a42802 ("iio: adc: ad7173: add AD7173 driver")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxx>
---
drivers/iio/adc/ad7173.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
index 6c4ed10ae580..67821c889010 100644
--- a/drivers/iio/adc/ad7173.c
+++ b/drivers/iio/adc/ad7173.c
@@ -712,15 +712,24 @@ static struct ad7173_channel_config *
ad7173_find_live_config(struct ad7173_state *st, struct ad7173_channel_config *cfg)
{
struct ad7173_channel_config *cfg_aux;
- ptrdiff_t cmp_size;
int i;
- cmp_size = sizeof_field(struct ad7173_channel_config, config_props);
+ BUILD_BUG_ON(sizeof_field(struct ad7173_channel_config, config_props) !=
+ sizeof(struct {
+ bool bipolar;
+ bool input_buf;
+ u8 odr;
+ u8 ref_sel;
+ }));
+
for (i = 0; i < st->num_channels; i++) {
cfg_aux = &st->channels[i].cfg;
if (cfg_aux->live &&
- !memcmp(&cfg->config_props, &cfg_aux->config_props, cmp_size))
+ cfg->bipolar == cfg_aux->bipolar &&
+ cfg->input_buf == cfg_aux->input_buf &&
+ cfg->odr == cfg_aux->odr &&
+ cfg->ref_sel == cfg_aux->ref_sel)
return cfg_aux;
}
return NULL;
--
2.47.1
