hwmon: (lm73) Make detection less problematic

Word reads can cause trouble with some I2C devices, so do as much
detection as we can using only byte reads, and only use a word read in
the end to confirm the positive match. Also properly handle read
errors.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Robert Casanova <robertcasanova@nanometrics.ca>

1 files changed, 18 insertions, 4 deletions

diff --git a/drivers/hwmon/lm73.c b/drivers/hwmon/lm73.c
index 29b9030d42c..24be17608fb 100644
--- a/drivers/hwmon/lm73.c
+++ b/drivers/hwmon/lm73.c
@@ -150,17 +150,31 @@ static int lm73_detect(struct i2c_client *new_client,
                         struct i2c_board_info *info)
 {
         struct i2c_adapter *adapter = new_client->adapter;
-        u16 id;
-        u8 ctrl;
+        int id, ctrl, conf;
 
         if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
                                         I2C_FUNC_SMBUS_WORD_DATA))
                 return -ENODEV;
 
+        /*
+         * Do as much detection as possible with byte reads first, as word
+         * reads can confuse other devices.
+         */
+        ctrl = i2c_smbus_read_byte_data(new_client, LM73_REG_CTRL);
+        if (ctrl < 0 || (ctrl & 0x10))
+                return -ENODEV;
+
+        conf = i2c_smbus_read_byte_data(new_client, LM73_REG_CONF);
+        if (conf < 0 || (conf & 0x0c))
+                return -ENODEV;
+
+        id = i2c_smbus_read_byte_data(new_client, LM73_REG_ID);
+        if (id < 0 || id != (LM73_ID & 0xff))
+                return -ENODEV;
+
         /* Check device ID */
         id = i2c_smbus_read_word_data(new_client, LM73_REG_ID);
-        ctrl = i2c_smbus_read_byte_data(new_client, LM73_REG_CTRL);
-        if ((id != LM73_ID) || (ctrl & 0x10))
+        if (id < 0 || id != LM73_ID)
                 return -ENODEV;
 
         strlcpy(info->type, "lm73", I2C_NAME_SIZE);