[PATCH] iio: proximity: sx9324: Correct proximity channel resolution
From: Zhang Jie
Date: Tue Aug 18 2026 - 03:30:14 EST
The proximity channels were previously defined with 12 realbits.
However, PROXDIFF is read from RegDiffMsb (0x65) and RegDiffLsb
(0x66). The SX9324 datasheet assigns bits 7:0 of each register to
PROXDIFF and documents it as a signed two's-complement value
(Revision 3, Section 8, Table 8, page 43). In contrast, RegOffsetMsb
explicitly marks bits 7:6 as reserved. Thus, PROXDIFF is a 16-bit
signed value.
With realbits = 12, sx_common_read_proximity() uses bit 11 as the
sign bit in sign_extend32(), causing samples outside the 12-bit
signed range to wrap into the [-2048, 2047] range.
Correct the realbits value to 16 to accurately reflect the hardware.
Tested on an SX9324-based device: a phase 0 DIFF readback of 0x7fff
was reported as -1 before this change and as 32767 afterward.
Fixes: 4c18a890dff8 ("iio:proximity:sx9324: Add SX9324 support")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Zhang Jie <zhangjie14@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
---
drivers/iio/proximity/sx9324.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iio/proximity/sx9324.c b/drivers/iio/proximity/sx9324.c
index 36c45d101336..de6176fd8d47 100644
--- a/drivers/iio/proximity/sx9324.c
+++ b/drivers/iio/proximity/sx9324.c
@@ -223,7 +223,7 @@ static const struct iio_chan_spec_ext_info sx9324_channel_ext_info[] = {
.scan_index = idx, \
.scan_type = { \
.sign = 's', \
- .realbits = 12, \
+ .realbits = 16, \
.storagebits = 16, \
.endianness = IIO_BE, \
}, \
--
2.53.0