displayio: Fix matrixportal crash

jepler · jepler · commit b1592564b286 · 2020-10-02T15:07:36.000-05:00
An RGBMatrix has no bus and no bus_free method. It is always possible to refresh the display. This was not a problem before, but the fix I suggested (adafruit#3449) added a call to core_bus_free when a FramebufferDisplay was being refreshed. This was not caught during testing. This is a band-aid fix and it brings to light a second problem in which a SharpDisplay + FrameBuffer will not have a 'bus' object, and yet does operate using a shared SPI bus. This kind of display will need a "bus-free" like function to be added, or it can have problems like adafruit#3309.
diff --git a/shared-module/displayio/display_core.c b/shared-module/displayio/display_core.c
@@ -197,7 +197,7 @@ bool displayio_display_core_get_dither(displayio_display_core_t* self){
 }
 
 bool displayio_display_core_bus_free(displayio_display_core_t *self) {
-    return self->bus_free(self->bus);
+    return !self->bus || self->bus_free(self->bus);
 }
 
 bool displayio_display_core_begin_transaction(displayio_display_core_t* self) {

Original file line number	Diff line number	Diff line change
`@@ -197,7 +197,7 @@ bool displayio_display_core_get_dither(displayio_display_core_t* self){`
`197`	`197`	`}`
`198`	`198`
`199`	`199`	`bool displayio_display_core_bus_free(displayio_display_core_t *self) {`
`200`		`- return self->bus_free(self->bus);`
	`200`	`+ return !self->bus \|\| self->bus_free(self->bus);`
`201`	`201`	`}`
`202`	`202`
`203`	`203`	`bool displayio_display_core_begin_transaction(displayio_display_core_t* self) {`