i2c_transfer_alloc_t
i2c_transfer_alloc_t *i2cw;
size = sizeof (i2c_transfer_alloc_t) + rlen + wlen;
sizeof (i2c_transfer_alloc_t);
sizeof (i2c_transfer_alloc_t) + wlen;
i2c_transfer_alloc_t *i2cw = (i2c_transfer_alloc_t *)i2c_tran;