Nick some aspects from the as3525 ascodec driver to improve throughput in
the beast's SPI communications by switching tranfer descriptors to the
caller's stack and getting rid of thread synchronization.
Fix a bug that suddenly became obvious that could permanently stall the SPI
driver because all data could be shifted out before the interrupt could get
serviced. In that case, it needs a kick to restart it. Should probably put
the SPI interrupt priority above DVFS.
A tweak to the event registration interface to simplify it.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31353 a1c6a512-1295-4272-9138-f99709370657
1) Rework event handling and static registration mechanism. No target-
specific code in mc13783 driver. GPIO event driver interfaces more
cleanly.
2) Somewhat related - enable thread priority for bootloader which is
desireable here (ffs is used for GPIO event enabling anyway and that
goes along with priority).
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17593 a1c6a512-1295-4272-9138-f99709370657
