esp32/mpconfigport: Don't hang when machine.bootloader isn't supported.

Currently only the Arduino Nano ESP32 defines a machine.bootloader handler
for ESP32.  All other boards will intentionally hang.

There is no error message, nor is a NotImplementedError raised.  There's no
indication if Micropython has crashed, or if the bootloader was entered but
USB is not working, which is a real problem the ESP32 bootloader has.  It's
not possible escape from this hang with ^C or any other means besides
physical access to the reset pin or the ability to cycle power.

Change this to only define an implementation of machine.bootloader() when
there is a handler for it.

Signed-off-by: Trent Piepho <tpiepho@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/ports/esp32/modmachine.c b/ports/esp32/modmachine.c
index 6e6a57896..a61d381e0 100755..100644
--- a/ports/esp32/modmachine.c
+++ b/ports/esp32/modmachine.c
@@ -220,11 +220,13 @@ static mp_int_t mp_machine_reset_cause(void) {
     }
 }
 
+#ifdef MICROPY_BOARD_ENTER_BOOTLOADER
 NORETURN void mp_machine_bootloader(size_t n_args, const mp_obj_t *args) {
     MICROPY_BOARD_ENTER_BOOTLOADER(n_args, args);
     for (;;) {
     }
 }
+#endif
 
 void machine_init(void) {
     is_soft_reset = 0;