Revert "power: supply: sbs-battery: simplify read_read_string_data"

The commit is a nice cleanup, but breaks booting on exynos5 based
chromebooks. It's seems to come down to exynos5's i2c driver not
implementing I2C_FUNC_SMBUS_READ_BLOCK_DATA. It's not yet clear
why that breaks boot / massively slows it down when userspace
starts, so revert the problematic patch.

This reverts commit c4b12a2f.
Signed-off-by: NSebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/sbs-battery.c

@@ -267,32 +267,66 @@ static int sbs_read_string_data(struct i2c_client *client, u8 address,
 				char *values)
 {
 	struct sbs_info *chip = i2c_get_clientdata(client);
-	int retries = chip->i2c_retry_count;
-	s32 ret = 0;
+	s32 ret = 0, block_length = 0;
+	int retries_length, retries_block;
+	u8 block_buffer[I2C_SMBUS_BLOCK_MAX + 1];
 
+	retries_length = chip->i2c_retry_count;
+	retries_block = chip->i2c_retry_count;
+
+	/* Adapter needs to support these two functions */
 	if (!i2c_check_functionality(client->adapter,
-				     I2C_FUNC_SMBUS_READ_BLOCK_DATA)) {
+				     I2C_FUNC_SMBUS_BYTE_DATA |
+				     I2C_FUNC_SMBUS_I2C_BLOCK)){
 		return -ENODEV;
 	}
 
+	/* Get the length of block data */
+	while (retries_length > 0) {
+		ret = i2c_smbus_read_byte_data(client, address);
+		if (ret >= 0)
+			break;
+		retries_length--;
+	}
+
+	if (ret < 0) {
+		dev_dbg(&client->dev,
+			"%s: i2c read at address 0x%x failed\n",
+			__func__, address);
+		return ret;
+	}
+
+	/* block_length does not include NULL terminator */
+	block_length = ret;
+	if (block_length > I2C_SMBUS_BLOCK_MAX) {
+		dev_err(&client->dev,
+			"%s: Returned block_length is longer than 0x%x\n",
+			__func__, I2C_SMBUS_BLOCK_MAX);
+		return -EINVAL;
+	}
+
 	/* Get the block data */
-	while (retries > 0) {
-		ret = i2c_smbus_read_block_data(client, address, values);
+	while (retries_block > 0) {
+		ret = i2c_smbus_read_i2c_block_data(
+				client, address,
+				block_length + 1, block_buffer);
 		if (ret >= 0)
 			break;
-		retries--;
+		retries_block--;
 	}
 
 	if (ret < 0) {
-		dev_dbg(&client->dev, "%s: failed to read block 0x%x: %d\n",
-			__func__, address, ret);
+		dev_dbg(&client->dev,
+			"%s: i2c read at address 0x%x failed\n",
+			__func__, address);
 		return ret;
 	}
 
-	/* add string termination */
-	values[ret] = '\0';
+	/* block_buffer[0] == block_length */
+	memcpy(values, block_buffer + 1, block_length);
+	values[block_length] = '\0';
 
-	return 0;
+	return ret;
 }
 
 static int sbs_write_word_data(struct i2c_client *client, u8 address,
@@ -514,7 +548,14 @@ static int sbs_get_battery_property(struct i2c_client *client,
 static int sbs_get_battery_string_property(struct i2c_client *client,
 	int reg_offset, enum power_supply_property psp, char *val)
 {
-	return sbs_read_string_data(client, sbs_data[reg_offset].addr, val);
+	s32 ret;
+
+	ret = sbs_read_string_data(client, sbs_data[reg_offset].addr, val);
+
+	if (ret < 0)
+		return ret;
+
+	return 0;
 }
 
 static void  sbs_unit_adjustment(struct i2c_client *client,