[PATCH] hwmon: (lm75) Strengthen detect function

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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.

Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
 drivers/hwmon/lm75.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/lm75.c b/drivers/hwmon/lm75.c
index f58439b..6753fd9 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) {
-- 
1.9.1


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