On 2011-08-31 10:25, Peter Maydell wrote: > On 30 August 2011 20:28, Jan Kiszka <jan.kis...@web.de> wrote: >> Yes, that's the current state. Once we have bidirectional IRQ links in >> place (pushing downward, querying upward - required to skip IRQ routers >> for fast, lockless deliveries), that should change again. > > Can you elaborate a bit more on this? I don't think anybody has > proposed links with their own internal state before in the qdev/qom > discussions...
That basic idea is to allow a) a discovery of the currently active IRQ path from source to sink (that would be possible via QOM just using forward links) b) skip updating the states of IRQ routers in the common case, just signaling directly the sink from the source (to allow in-kernel IRQ delivery or to skip taking some device locks). Whenever some router is queried for its current IRQ line state, it would have to ask the preceding IRQ source for its state. So we need a backward link. We haven't thought about how this could be implemented in details yet though. Among other things, it heavily depends on the final QOM design. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
