Fix FourWire and I2CDisplay argument validation

[FoamyGuy]

resolves #5449

Check spi argument for None and raise a ValueError instead of crashing.

Tested successfully with code from the issue. on:

Adafruit CircuitPython 7.0.0-176-gf13db0d0e-dirty on 2021-10-09; Raspberry Pi Pico with rp2040
Board ID:raspberry_pi_pico

With the build from the PR it does successfully raise the ValueError instead of crashing into the broken state.

[ladyada]

didnt test but lgtm

[microdev1]

@FoamyGuy Thanks for catching & fixing this issue. One suggestion, looks good otherwise.

[jepler]

Thanks, good find!

I wonder if you can't use mp_arg_validate_type with &busio_spi_type instead. as it stands, won't passing in something else, like the number 7 or an empty list (or even, more plausibly, a bitbangio SPI object) still cause problems?

[jepler]

(see above comment)

[FoamyGuy]

Latest commit changes to use mp_arg_validate_type instead of the if None. This has the benefit of already having it's own error message so we also don't end up needing the string / translations with this method. Thanks for the tip @jepler

[jepler]

I'm not sure why more boards didn't fail, but it seems you need to include the header that gives the declaration of busio_spi_type:

--- a/shared-bindings/displayio/FourWire.c
+++ b/shared-bindings/displayio/FourWire.c
@@ -32,6 +32,7 @@
 #include "py/binary.h"
 #include "py/objproperty.h"
 #include "py/runtime.h"
+#include "shared-bindings/busio/SPI.h"
 #include "shared-bindings/displayio/Group.h"
 #include "shared-bindings/microcontroller/Pin.h"
 #include "shared-bindings/util.h"

[jepler]

Do you mind checking out the I2CDisplay code while you're working on it?

[FoamyGuy]

Do you mind checking out the I2CDisplay code while you're working on it?

Indeed I2CDisplay does exhibit a similar hard crash with this reproducer:

import board
import displayio
import adafruit_displayio_ssd1306

displayio.release_displays()
oled_reset = board.D9

# Use for I2C
i2c = board.I2C()

display_bus = displayio.I2CDisplay(None, device_address=0x3C, reset=oled_reset)

WIDTH = 128
HEIGHT = 32  # Change to 64 if needed

display = adafruit_displayio_ssd1306.SSD1306(display_bus, width=WIDTH, height=HEIGHT)

I'll put a fix in for it as well.

[FoamyGuy]

Latest commit fixes the SPI include and implements similar validation in I2CDisplay

[jepler]

Thank you, so clean & to the point now. Nice to have those hardfaults fixed.