i2c: Share the I2C device presence detection code

Use the same I2C device presence detection code for legacy and new
device detection functions. This is more consistent and makes the code
smaller.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Matthieu Castet <castet.matthieu@free.fr>

drivers/i2c/i2c-core.c

@@ -1277,6 +1277,41 @@ EXPORT_SYMBOL(i2c_master_recv);
  * ----------------------------------------------------
  */
 
+/*
+ * Legacy default probe function, mostly relevant for SMBus. The default
+ * probe method is a quick write, but it is known to corrupt the 24RF08
+ * EEPROMs due to a state machine bug, and could also irreversibly
+ * write-protect some EEPROMs, so for address ranges 0x30-0x37 and 0x50-0x5f,
+ * we use a short byte read instead. Also, some bus drivers don't implement
+ * quick write, so we fallback to a byte read in that case too.
+ * On x86, there is another special case for FSC hardware monitoring chips,
+ * which want regular byte reads (address 0x73.) Fortunately, these are the
+ * only known chips using this I2C address on PC hardware.
+ * Returns 1 if probe succeeded, 0 if not.
+ */
+static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
+{
+	int err;
+	union i2c_smbus_data dummy;
+
+#ifdef CONFIG_X86
+	if (addr == 0x73 && (adap->class & I2C_CLASS_HWMON)
+	 && i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE_DATA))
+		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+				     I2C_SMBUS_BYTE_DATA, &dummy);
+	else
+#endif
+	if ((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50
+	 || !i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
+		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+				     I2C_SMBUS_BYTE, &dummy);
+	else
+		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0,
+				     I2C_SMBUS_QUICK, NULL);
+
+	return err >= 0;
+}
+
 static int i2c_detect_address(struct i2c_client *temp_client,
 			      struct i2c_driver *driver)
 {
@@ -1297,24 +1332,9 @@ static int i2c_detect_address(struct i2c_client *temp_client,
 		return 0;
 
 	/* Make sure there is something at this address */
-	if (addr == 0x73 && (adapter->class & I2C_CLASS_HWMON)) {
-		/* Special probe for FSC hwmon chips */
-		union i2c_smbus_data dummy;
-
-		if (i2c_smbus_xfer(adapter, addr, 0, I2C_SMBUS_READ, 0,
-				   I2C_SMBUS_BYTE_DATA, &dummy) < 0)
-			return 0;
-	} else {
-		if (i2c_smbus_xfer(adapter, addr, 0, I2C_SMBUS_WRITE, 0,
-				   I2C_SMBUS_QUICK, NULL) < 0)
+	if (!i2c_default_probe(adapter, addr))
 		return 0;
 
-		/* Prevent 24RF08 corruption */
-		if ((addr & ~0x0f) == 0x50)
-			i2c_smbus_xfer(adapter, addr, 0, I2C_SMBUS_WRITE, 0,
-				       I2C_SMBUS_QUICK, NULL);
-	}
-
 	/* Finally call the custom detection function */
 	memset(&info, 0, sizeof(struct i2c_board_info));
 	info.addr = addr;
@@ -1420,29 +1440,9 @@ i2c_new_probed_device(struct i2c_adapter *adap,
 			continue;
 		}
 
-		/* Test address responsiveness
-		   The default probe method is a quick write, but it is known
-		   to corrupt the 24RF08 EEPROMs due to a state machine bug,
-		   and could also irreversibly write-protect some EEPROMs, so
-		   for address ranges 0x30-0x37 and 0x50-0x5f, we use a byte
-		   read instead. Also, some bus drivers don't implement
-		   quick write, so we fallback to a byte read it that case
-		   too. */
-		if ((addr_list[i] & ~0x07) == 0x30
-		 || (addr_list[i] & ~0x0f) == 0x50
-		 || !i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK)) {
-			union i2c_smbus_data data;
-
-			if (i2c_smbus_xfer(adap, addr_list[i], 0,
-					   I2C_SMBUS_READ, 0,
-					   I2C_SMBUS_BYTE, &data) >= 0)
+		/* Test address responsiveness */
+		if (i2c_default_probe(adap, addr_list[i]))
 			break;
-		} else {
-			if (i2c_smbus_xfer(adap, addr_list[i], 0,
-					   I2C_SMBUS_WRITE, 0,
-					   I2C_SMBUS_QUICK, NULL) >= 0)
-				break;
-		}
 	}
 
 	if (addr_list[i] == I2C_CLIENT_END) {