mfd: Clarify twl4030 return value for read and write

We should be checking if all the messages were tranferred. If not, then we
should propagate the i2c core error code or EIO.
Currently we return success (0) even if none of messages were transferred
successfully.
Signed-off-by: Amit Kucheria <amit.kucheria@verdurent.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl4030-core.c

@@ -306,10 +306,17 @@ int twl4030_i2c_write(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes)
 	ret = i2c_transfer(twl->client->adapter, twl->xfer_msg, 1);
 	mutex_unlock(&twl->xfer_lock);
 
-	/* i2cTransfer returns num messages.translate it pls.. */
-	if (ret >= 0)
-		ret = 0;
-	return ret;
+	/* i2c_transfer returns number of messages transferred */
+	if (ret != 1) {
+		pr_err("%s: i2c_write failed to transfer all messages\n",
+			DRIVER_NAME);
+		if (ret < 0)
+			return ret;
+		else
+			return -EIO;
+	} else {
+		return 0;
+	}
 }
 EXPORT_SYMBOL(twl4030_i2c_write);
 
@@ -358,10 +365,17 @@ int twl4030_i2c_read(u8 mod_no, u8 *value, u8 reg, unsigned num_bytes)
 	ret = i2c_transfer(twl->client->adapter, twl->xfer_msg, 2);
 	mutex_unlock(&twl->xfer_lock);
 
-	/* i2cTransfer returns num messages.translate it pls.. */
-	if (ret >= 0)
-		ret = 0;
-	return ret;
+	/* i2c_transfer returns number of messages transferred */
+	if (ret != 2) {
+		pr_err("%s: i2c_read failed to transfer all messages\n",
+			DRIVER_NAME);
+		if (ret < 0)
+			return ret;
+		else
+			return -EIO;
+	} else {
+		return 0;
+	}
 }
 EXPORT_SYMBOL(twl4030_i2c_read);