On Mon, 2013-11-25 at 04:50 +0100, David Henningsson wrote: > On 11/20/2013 10:26 AM, Tanu Kaskinen wrote: > > Router modules will create a pa_router object, and extend its > > functionality with callbacks. There can be only one router in the > > system at a time. At this first stage, the only functionality the base > > pa_router is to notify the router modules about new and removed nodes. > > Then there is another concept we can take away to keep it simple atm - > there is no need to have a "base pa_router", you can just notify the > router implementation through hooks instead. One point of pa_router is that it's ensured that there's only one router loaded at a time in the system. That's useful, because a router is responsible of managing all stream routing and profile and port activation, so having two routers in the system would make the behaviour unpredictable when those two routers conflict. Another benefit of a dedicated object is that it's easier to define a proper interface for the routers. It's usually not documented what a hook callback is expected to do. I failed with the naming and documentation of the pa_router_add_node() function and the associated callback, though. That really isn't any better than a hook in terms of interface clarity. I should have named it pa_router_set_initial_routing() or something like that, because setting the initial routing for a node is what the router is expected to do. One more benefit of not using hooks is that hooks can have just one "call data" parameter. I extended the interface of pa_router.add_node() yesterday: int (*add_node)(pa_router *router, pa_node *node, pa_node **initial_connections, unsigned n_initial_connections); So it can now return an error, and it has access to the requested initial connections. This is more cumbersome to do with hooks. I have to either define a new struct holding the connection request data that will be passed to the hook, or I'll have to add fields to pa_node that contain that same information (not nice, because the information is relevant only at the node creation phase). Those were the reasons why I prefer pa_router over just using hooks. Tell me if you changed your mind and you prefer pa_router too, otherwise I'll remove pa_router for now and make do with hooks. -- Tanu
