Fix erroneous claim of board.I2C() by deinited display.

cwalther · cwalther · commit 1117edae63df · 2020-10-26T22:44:38.000+01:00
At the end of a session that called displayio.release_displays() (and did not initialize a new display), a board.I2C() bus that was previously used by a display would wrongly be considered still in use. While I can’t think of any unrecoverable problem this would cause in the next session, it violates the assumption that a soft reboot resets everything not needed by displays, potentially leading to confusion. By itself, this change does not fix the problem yet - rather, it introduces the same issue as in adafruit#3581 for SPI. This needs to be solved in the same way for I2C and SPI.
diff --git a/shared-module/board/__init__.c b/shared-module/board/__init__.c
@@ -139,7 +139,7 @@ void reset_board_busses(void) {
     bool display_using_i2c = false;
     #if CIRCUITPY_DISPLAYIO
     for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
-        if (displays[i].i2cdisplay_bus.bus == i2c_singleton) {
+        if (displays[i].bus_base.type == &displayio_i2cdisplay_type && displays[i].i2cdisplay_bus.bus == i2c_singleton) {
             display_using_i2c = true;
             break;
         }

Original file line number	Diff line number	Diff line change
`@@ -139,7 +139,7 @@ void reset_board_busses(void) {`
`139`	`139`	`bool display_using_i2c = false;`
`140`	`140`	`#if CIRCUITPY_DISPLAYIO`
`141`	`141`	`for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {`
`142`		`- if (displays[i].i2cdisplay_bus.bus == i2c_singleton) {`
	`142`	`+ if (displays[i].bus_base.type == &displayio_i2cdisplay_type && displays[i].i2cdisplay_bus.bus == i2c_singleton) {`
`143`	`143`	`display_using_i2c = true;`
`144`	`144`	`break;`
`145`	`145`	`}`