On Tue, Dec 15, 2015 at 11:04:51PM -0700, Devin Reade wrote: > The usbd_open_pipe_intr(9) man page discusses the usbd_callback type and > the usbd_transfer(9) man page mentions the associated interrupt context in > which (presumably) that callback executes. > > Are there any particular restrictions that apply while running from within > that interrupt context?
tsleep(9) may not be called. There may be more, but I've gotten by just fine with the above, so far :) > In particular, I'm wondering if it's safe to invoke add_true_randomness(9) > from > within that interrupt context. Yes, that should be safe. > In addition to the specific answer, pointers to docs/references are welcome. The best way to learn about these things is to start writing small but functional kernel diffs and get them reviewed. The "Design and Implementation of *BSD" books might help with getting the bigger picture. The newer ones are rather FreeBSD-specific but the older ones (for 4.xBSD) do apply to OpenBSD in lots of ways (but not in every way). Any such book will only provide very high-level information and you will have to read the code for details.
