This error seems... strange.
```
$ glasgow run spi-controller -V 3.3 --cs B0 --sck B1 --copi B2 --cipo B3 -m 3 -f 100
usage: glasgow run spi-controller [-h] [-V SPEC] [--cs PIN] [--sck PIN] [--copi PIN] [--cipo PIN] [-m MODE] [-f FREQ]
                                  DATA [DATA ...]
glasgow run spi-controller: error: argument -m/--mode: invalid choice: '3' (choose from 0, 1, 2, 3)
```