hwmon: (nct6775) Do not accept force_id unless chip is found
Since commit 698a7c24a544 ("hwmon: (nct6775) Support two SuperIO chips
in the same system"), the driver supports two Super-IO chips. This has
the undesirable side effect that force_id always detects a second chip
at address 0xfff8, even if no chip exists at that address.
nct6775: Found NCT6793D or compatible chip at 0x4e:0xfff8
If no chip at all is found at a given SIO address, it does not make sense
to instantiate it. Limit force_id to only work if some chip is found,
that is if the chip ID returns a value other than 0xffff.
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
diff --git a/drivers/hwmon/nct6775.c b/drivers/hwmon/nct6775.c
index d087a8e..7859a30 100644
--- a/drivers/hwmon/nct6775.c
+++ b/drivers/hwmon/nct6775.c
@@ -4232,11 +4232,11 @@
if (err)
return err;
- if (force_id)
+ val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8) |
+ superio_inb(sioaddr, SIO_REG_DEVID + 1);
+ if (force_id && val != 0xffff)
val = force_id;
- else
- val = (superio_inb(sioaddr, SIO_REG_DEVID) << 8)
- | superio_inb(sioaddr, SIO_REG_DEVID + 1);
+
switch (val & SIO_ID_MASK) {
case SIO_NCT6106_ID:
sio_data->kind = nct6106;
