i2c: Restore i2c_smbus_read_block_data

Add back the i2c_smbus_read_block_data helper function, it is needed
by the upcoming lm93 hardware monitoring driver and possibly others.
Signed-off-by: NJean Delvare <khali@linux-fr.org>

drivers/i2c/i2c-core.c

@@ -1298,6 +1298,22 @@ s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
 }
 EXPORT_SYMBOL(i2c_smbus_write_word_data);
 
+/* Returns the number of read bytes */
+s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command,
+			      u8 *values)
+{
+	union i2c_smbus_data data;
+
+	if (i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+	                   I2C_SMBUS_READ, command,
+	                   I2C_SMBUS_BLOCK_DATA, &data))
+		return -1;
+
+	memcpy(values, &data.block[1], data.block[0]);
+	return data.block[0];
+}
+EXPORT_SYMBOL(i2c_smbus_read_block_data);
+
 s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command,
 			       u8 length, const u8 *values)
 {

include/linux/i2c.h

@@ -82,6 +82,9 @@ extern s32 i2c_smbus_write_byte_data(struct i2c_client * client,
 extern s32 i2c_smbus_read_word_data(struct i2c_client * client, u8 command);
 extern s32 i2c_smbus_write_word_data(struct i2c_client * client,
                                      u8 command, u16 value);
+/* Returns the number of read bytes */
+extern s32 i2c_smbus_read_block_data(struct i2c_client *client,
+				     u8 command, u8 *values);
 extern s32 i2c_smbus_write_block_data(struct i2c_client * client,
 				      u8 command, u8 length,
 				      const u8 *values);