The Filter is called on the primary hardware interrupt context. Very

little of the system is available at this time. The IOLog doc says

that you can't run at interrupt time, the sub text is that you can't

call it at hardware interrupt time, or in IOKit terms at Filter time.

Does this help?

Sure ... but I don't see the sub text that you mention in the docs I'm looking at, maybe there's a better source for documentation ... I'm referring to: http://developer.apple.com/techpubs/macosx/Darwin/Reference/Kernel/IOLib/Fun ctions/Functions.html <Hopefully the link won't wrap - converted message to HTML to keep that from happening.> Thanks, -Chris