hwmon: (lm75) Strengthen detect function

A chip returning 0x00 in all registers is erroneously detected
as LM75. Check hysteresis and temperature limit registers and
abort if both are 0 to reduce the likelyhood for this to happen.

Reviewed-by: Rob Coulson <rob.coulson@gmail.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index f58439b817b5..6753fd940c76 100644
--- a/drivers/hwmon/lm75.c
+++ b/drivers/hwmon/lm75.c
@@ -415,6 +415,12 @@ static int lm75_detect(struct i2c_client *new_client,
                  || i2c_smbus_read_byte_data(new_client, 7) != os)
                         return -ENODEV;
         }
+        /*
+         * It is very unlikely that this is a LM75 if both
+         * hysteresis and temperature limit registers are 0.
+         */
+        if (hyst == 0 && os == 0)
+                return -ENODEV;
 
         /* Addresses cycling */
         for (i = 8; i <= 248; i += 40) {