Reconnect old drainage pipe, ventilation, negative pressure

Hey I drilled the drain pipe from the attic to the 2nd floor and connected it to the toilet below to have a toilet connection for the attic. (From the 2nd floor upward, only an 80 mm pipe was used, which is unsuitable for a toilet.) Now the question about the pressure: should I run a ventilation pipe up there, or is it enough if the old drain pipe also serves as a pipe for pressure and so on?