-typedef int (*i2c_writeRope_t)(I2c *i2c, uint16_t slave_addr, int flags, const void *buf, size_t len, ...);
-typedef int (*i2c_readRope_t)(I2c *i2c, uint16_t slave_addr, int flags, void *buf, size_t len, ...);
+struct I2c;
+
+typedef int (*i2c_writeRope_t)(struct I2c *i2c, uint16_t slave_addr, int flags, const void *buf, size_t len, ...);
+typedef int (*i2c_readRope_t)(struct I2c *i2c, uint16_t slave_addr, int flags, void *buf, size_t len, ...);