hwmon: (tmp421) Strengthen detect function

Not all supported chips support the entire I2C address range.
Only accept specific chips at the addresses supported by that chip.
Check for invalid values in conversion rate and status registers.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>

2 files changed, 16 insertions, 2 deletions

diff --git a/Documentation/hwmon/tmp421 b/Documentation/hwmon/tmp421
index 0cf07f824741..d0e77143077f 100644
--- a/Documentation/hwmon/tmp421
+++ b/Documentation/hwmon/tmp421
@@ -8,11 +8,11 @@ Supported chips:
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
   * Texas Instruments TMP422
     Prefix: 'tmp422'
-    Addresses scanned: I2C 0x2a, 0x4c, 0x4d, 0x4e and 0x4f
+    Addresses scanned: I2C 0x4c, 0x4d, 0x4e and 0x4f
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
   * Texas Instruments TMP423
     Prefix: 'tmp423'
-    Addresses scanned: I2C 0x2a, 0x4c, 0x4d, 0x4e and 0x4f
+    Addresses scanned: I2C 0x4c and 0x4d
     Datasheet: http://focus.ti.com/docs/prod/folders/print/tmp421.html
 
 Authors:
diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
index 7bab7a9bedc6..9438c1bd5d59 100644
--- a/drivers/hwmon/tmp421.c
+++ b/drivers/hwmon/tmp421.c
@@ -42,6 +42,7 @@ static const unsigned short normal_i2c[] = { 0x2a, 0x4c, 0x4d, 0x4e, 0x4f,
 enum chips { tmp421, tmp422, tmp423 };
 
 /* The TMP421 registers */
+#define TMP421_STATUS_REG                       0x08
 #define TMP421_CONFIG_REG_1                     0x09
 #define TMP421_CONVERSION_RATE_REG              0x0B
 #define TMP421_MANUFACTURER_ID_REG              0xFE
@@ -235,6 +236,7 @@ static int tmp421_detect(struct i2c_client *client,
         enum chips kind;
         struct i2c_adapter *adapter = client->adapter;
         const char *names[] = { "TMP421", "TMP422", "TMP423" };
+        int addr = client->addr;
         u8 reg;
 
         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
@@ -244,15 +246,27 @@ static int tmp421_detect(struct i2c_client *client,
         if (reg != TMP421_MANUFACTURER_ID)
                 return -ENODEV;
 
+        reg = i2c_smbus_read_byte_data(client, TMP421_CONVERSION_RATE_REG);
+        if (reg & 0xf8)
+                return -ENODEV;
+
+        reg = i2c_smbus_read_byte_data(client, TMP421_STATUS_REG);
+        if (reg & 0x7f)
+                return -ENODEV;
+
         reg = i2c_smbus_read_byte_data(client, TMP421_DEVICE_ID_REG);
         switch (reg) {
         case TMP421_DEVICE_ID:
                 kind = tmp421;
                 break;
         case TMP422_DEVICE_ID:
+                if (addr == 0x2a)
+                        return -ENODEV;
                 kind = tmp422;
                 break;
         case TMP423_DEVICE_ID:
+                if (addr != 0x4c && addr != 0x4d)
+                        return -ENODEV;
                 kind = tmp423;
                 break;
         default: