[plug] Scheduling and Blocking Explained

[Tom Atkinson]

Brad,

Thanks very much for taking the time to give us a good rundown on what
was happening and why.  My knowledge of how device drivers work has been
given a much needed refresher!

Just one comment though, on your statement about non-blocking
reads/writes:

> Non blocking IO is just the opposite.
> You do a write() and your program jams that data in to the drivers buffer

On the driver I wrote, if all the data could be written by the write
call, whether it was 1 byte or 512, it would be, otherwise, I would
immediately return EWOULDBLOCK (thus leaving it up to the caller to try
again later).

This errno is actually the same number as EAGAIN.

Cheers!
Tom Atkinson