[openib-general] [PATCH] RFC: allow send only registration from userspace

[Roland Dreier]

    Hal> It seems wasteful to have another thread just for polling
    Hal> these events.

Don't do that then.  The issue of which file descriptor the events
come from is orthogonal to how userspace handles them.  (Although
threads are pretty cheap)

Adding async events to the MAD file descriptor really messes up the
user/kernel interface.  Right now we, the umad devices are very easy
to understand: read() receives a MAD, write() sends a MAD, and ioctl()
sets up some control information related to sending and receiving
MADs.  I don't see a clean way to add async events into that.

Also, the current umad devices are per-port, while async events are
really per-device.  Adding some sort of filtering policy is just going
to generate yet more confusion.

If we want to move async events from the uverbs devices to dedicated
async event devices then I don't really have a problem with that.
That would save things like OpenSM from having to deal with the whole
verbs interface just to get events.

 - R.