Hi, > > What questions for example? > > This opens up different kind of possible replies, and error handling. > > With current proposal and needs, the reply (or absence of reply) is > entirely driven by the request. > > With your proposal, should all request have a reply?
Yes. > which makes a lot > more code synchronous, Why? You don't have to wait for the reply before sending the next request. Adding a request id to the messages might be useful, so it is possible to wait for a reply to a specific message without having to keeping track of all in-flight messages. > and complicates both sides unnecessarily. Having headers in the reply allows it to process them in generic code. There is a size header for the reply, so you can parse the stream without knowing what replay to expect. You can use the status field to indicate the payload, simliar to virtio-gpu which has response code OK_NODATA, some OK_$whatpayload and some ERR_$failure codes. You can dispatch based on the response/status code and run *fully* asynchronous without too much trouble. > > > Can we leave that for future protocol extensions negotiated with > > > GET/SET_PROTOCOL_FEATURES ? > > > > I don't think negotiating such a basic protocol change is a good idea. > > Well, then I would rather focus on improving protocol negociation, > rather than adding unnecessary protocol changes. > > Given that GET/SET_PROTOCOL_FEATURES is the first messages being sent, > why couldn't it have flags indicating new protocol revision? A properly structed reply allows a different approach in reply processing (see above). But that only works if it is in the protocol right from the start. As add-on feature it can't provide the benefits because the reply parser must be able to handle both protocol variants. cheers, Gerd
