This is a note to let you know that I've just added the patch titled
iio: pressure: ms5611: ms5611_prom_is_valid false negative bug
to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From fd39d9668f2ce9f4b05ad55e8c8d80c098073e0b Mon Sep 17 00:00:00 2001
From: Alexander Zangerl <az@xxxxxxxxxxxxxxxx>
Date: Wed, 20 Sep 2023 10:01:10 +1000
Subject: iio: pressure: ms5611: ms5611_prom_is_valid false negative bug
The ms5611 driver falsely rejects lots of MS5607-02BA03-50 chips
with "PROM integrity check failed" because it doesn't accept a prom crc
value of zero as legitimate.
According to the datasheet for this chip (and the manufacturer's
application note about the PROM CRC), none of the possible values for the
CRC are excluded - but the current code in ms5611_prom_is_valid() ends with
return crc_orig != 0x0000 && crc == crc_orig
Discussed with the driver author (Tomasz Duszynski) and he indicated that
at that time (2015) he was dealing with some faulty chip samples which
returned blank data under some circumstances and/or followed example code
which indicated CRC zero being bad.
As far as I can tell this exception should not be applied anymore; We've
got a few hundred custom boards here with this chip where large numbers
of the prom have a legitimate CRC value 0, and do work fine, but which the
current driver code wrongly rejects.
Signed-off-by: Alexander Zangerl <az@xxxxxxxxxxxxxxxx>
Fixes: c0644160a8b5 ("iio: pressure: add support for MS5611 pressure and temperature sensor")
Link: https://lore.kernel.org/r/2535-1695168070.831792@xxxxxxxxx.s3fx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
---
drivers/iio/pressure/ms5611_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/iio/pressure/ms5611_core.c b/drivers/iio/pressure/ms5611_core.c
index 627497e61a63..2fc706f9d8ae 100644
--- a/drivers/iio/pressure/ms5611_core.c
+++ b/drivers/iio/pressure/ms5611_core.c
@@ -76,7 +76,7 @@ static bool ms5611_prom_is_valid(u16 *prom, size_t len)
crc = (crc >> 12) & 0x000F;
- return crc_orig != 0x0000 && crc == crc_orig;
+ return crc == crc_orig;
}
static int ms5611_read_prom(struct iio_dev *indio_dev)
--
2.42.0
