DBus is unsuitable for high bandwidth data transfer. To facilitate this, dbus provides "file descriptor passing" feature that establishes direct connection between two peers.

Service framework should probably expose a direct channel like this to its clients.

Alternatively, all method invocations could be handled through this direct channel, with massive improvements to SFW performance (as we avoid context extra switch to daemon, validation, copying).

It's not clear what mechanism would take care of this in Symbian. Also, QDBus does not yet support file descriptor passing.