This change introduces new sleep_block() and sleep_unblock() functions
that control whether the sleep() function actually sleeps. This type of
behavior was already implemented in the DMA driver, since DMA access to
on-chip memory is paused when sleeping (on-chip memory being paused
itself), which would make waiting for a DMA transfer a freeze.
Because DMA transfers are now asynchronous, and USB transfers that may
involve on-chip memory are coming, this API change allows the DMA and
USB drivers to block the sleep() function so that user code can sleep()
for interrupts without having to worry about asynchronous tasks
requiring on-chip memory to complete.
Lephe
95dbec17ab
