Failure to compile for Teensy40

[robhamerling]

When building firmware with st7789_mpy for Teensy 4.0 I get the report:

/home/rob/upy/lib/st7789_mpy/st7789/st7789.c: In function 'write_cmd':
/home/rob/upy/lib/st7789_mpy/st7789/st7789.c:74:18: error: comparison between pointer and integer [-Werror]
   74 |     if (self->cs != GPIO_NUM_NC) {     \
      |                  ^~

and many similar lines.

I see in the comments in st7789.c that I may need to change type or value of GPIO_NUM_NC, and for the Teensy it probably needs to be a pointer type, perhaps &(-1) ?
Maybe an '#ifdef" need to be added for the Teensy?

[russhughes]

The GPIO_NUM_NC definition needs to be refactored. A quick workaround is to add CFLAGS_EXTRA="-DGPIO_NUM_NC=NULL" to your make command.

[robhamerling]

With this suggested workaround compilation succeeded and firmware works, thanks.