recommended method for hardware to report events to userspace?

[Chris Friesen <cfriesen@nortelnetworks.com>]

I'm doing some work on a SONET PHY and I was wondering what the recommended
method is for asynchronously reporting events to userspace.

I have some non-critical events (correctable ecc errors, etc) that I poll every
once in a while, but there are some critical events (loss of signal, for
instance) that I want to report immediately.

What is the usual way of doing this?  I see three possibilities: 1) the
userspace app could register its pid with the driver using ioctl() and on a
fault the interrupt handler in the driver could fire off a signal to the
registered pids to alert them that something happened, at which point they do
another ioctl() to find out exactly what it was,  2) use netlink to provide a
socket-based notification of what happened,  3) provide a file descriptor that
becomes readable when an event happens.

What's the Right Thing to do here?


Thanks,
Chris

-- 
Chris Friesen                    | MailStop: 043/33/F10  
Nortel Networks                  | work: (613) 765-0557
3500 Carling Avenue              | fax:  (613) 765-2986
Nepean, ON K2H 8E9 Canada        | email: cfriesen@nortelnetworks.com