This is refactoring to enable support for the two USB PHYs available on
some STM32F4 processors to be used at the same time. The F405/7 & F429
have two USB PHYs, others such as the F411 only have one PHY.
This has been tested separately on a pyb10 (USB_FS PHY) and F429DISC
(USB_HS PHY) to be able to invoke a REPL/USB. I have modified a PYBV10
to support two PHYs.
The long term objective is to support a 2nd USB PHY to be brought up as a
USB HOST, and possibly a single USB PHY to be OTG.
Currently nlr_jump_fail prints that there was an uncaught exception
but nothing about the exception.
This patch causes nlr_jump_failed to try to print the exception.
Given that printf was called on the line above, I think that
the call to mp_obj_print_exception has about as much likelyhood
of succeeding as the printf does.
When you use the USER button to perform a filesystem reset
at boot time then it wipes out the filesystem and creates
a new boot.py and main.py. With this patch these files are
executed after formatting, ensuring that pyb and machine modules
get imported.
Per CPython docs, "Registering a file descriptor that’s already registered
is not an error, and has the same effect as registering the descriptor
exactly once."
https://docs.python.org/3/library/select.html#select.poll.register
That's somewhat ambiguous, what's implemented here is that if fd si not
yet registered, it is registered. Otherwise, the effect is equivalent to
modify() method.