iio: adc: ad7124: fix config comparison

commit 2f6b92d0f69f04d9e2ea0db1228ab7f82f3173af upstream.

The ad7124_find_similar_live_cfg() computes the compare size by
substracting the address of the cfg struct from the address of the live
field. Because the live field is the first field in the struct, the
result is 0.

Also, the memcmp() call is made from the start of the cfg struct, which
includes the live and cfg_slot fields, which are not relevant for the
comparison.

Fix by grouping the relevant fields with struct_group() and use the
size of the group to compute the compare size; make the memcmp() call
from the address of the group.

Fixes: 7b8d045e497a ("iio: adc: ad7124: allow more than 8 channels")
Signed-off-by: Dumitru Ceclan <dumitru.ceclan@analog.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://patch.msgid.link/20240731-ad7124-fix-v1-2-46a76aa4b9be@analog.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index b9b206fcd748f585c53595f7da3ba13988c13acb..c56227f42a5a3665fc671cfa5e833ba87e658f09 100644 (file)
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -146,15 +146,18 @@ struct ad7124_chip_info {
 struct ad7124_channel_config {
        bool live;
        unsigned int cfg_slot;
-       enum ad7124_ref_sel refsel;
-       bool bipolar;
-       bool buf_positive;
-       bool buf_negative;
-       unsigned int vref_mv;
-       unsigned int pga_bits;
-       unsigned int odr;
-       unsigned int odr_sel_bits;
-       unsigned int filter_type;
+       /* Following fields are used to compare equality. */
+       struct_group(config_props,
+               enum ad7124_ref_sel refsel;
+               bool bipolar;
+               bool buf_positive;
+               bool buf_negative;
+               unsigned int vref_mv;
+               unsigned int pga_bits;
+               unsigned int odr;
+               unsigned int odr_sel_bits;
+               unsigned int filter_type;
+       );
 };
 
 struct ad7124_channel {
@@ -333,11 +336,12 @@ static struct ad7124_channel_config *ad7124_find_similar_live_cfg(struct ad7124_
        ptrdiff_t cmp_size;
        int i;
 
-       cmp_size = (u8 *)&cfg->live - (u8 *)cfg;
+       cmp_size = sizeof_field(struct ad7124_channel_config, config_props);
        for (i = 0; i < st->num_channels; i++) {
                cfg_aux = &st->channels[i].cfg;
 
-               if (cfg_aux->live && !memcmp(cfg, cfg_aux, cmp_size))
+               if (cfg_aux->live &&
+                   !memcmp(&cfg->config_props, &cfg_aux->config_props, cmp_size))
                        return cfg_aux;
        }