this temporarily takes ownership of pins because we need to clear edge
interrupts before waiting for them (otherwise we may wait indefinitely),
we want to clean up the dormant-wake bits after a wakeup, and doing
anything *else* with the input while we're waiting for a wakeup isn't
possible at all. doing it like this lets us not impose any cost on those
who don't use dormant wakes without entangling dormant waits too badly
with regular interrupt waits.
with uniform treatment of adc inputs it's easy enough to add a new
sampling method. dma sampling only supports one channel at the moment,
though round-robin sampling would be a simple extension (probably a new
trait that's implemented for Channel and &[Channel]). continuous dma as
proposed in #1608 also isn't done here, we'd expect that to be a
compound dma::Channel that internally splits a buffer in half and
dispatches callbacks or something like that.
this lets us treat pins and the temperature sensor uniformly using the
same interface. uniformity in turn lets us add more adc features without
combinatorial explosion of methods and types needed to handle them all.
so far only bank0 interrupts were processed and configured, even if a
qspi pin was given. this is obviously not the right thing to do, so
let's rectify that. the fact that no problems have shown up so far does
suggest that most, if not all, applications don't use this functionality
at all.
this will be mostly not useful to anyone since flash is attached to
qspi, and using flash chips that don't use the *entire* qspi interface
will severly slow down the chip. the code overhead is minimal right now,
but if we also fix interrupt support on qspi pins this will
change (adding more code to potentially hot paths, using more memory for
wakers that are never used, and preventing the qspi gpio irq from being
used in software interrupts as RTIC applications may want to do).
we'll need access to the pin io bank registers for an upcoming fix, and
having both `io` and `io_bank` or similar can get confusing quickly.
rename `io` to `gpio` to avoid this, and also match the type while there.
