displayio: check whether we locked the bus or not

Author: dhalbert

shared-module/busdisplay/BusDisplay.c

@@ -6,6 +6,7 @@
 
 #include "shared-bindings/busdisplay/BusDisplay.h"
 
+#include "py/mphal.h"
 #include "py/runtime.h"
 #if CIRCUITPY_FOURWIRE
 #include "shared-bindings/fourwire/FourWire.h"
@@ -16,6 +17,7 @@
 #if CIRCUITPY_PARALLELDISPLAYBUS
 #include "shared-bindings/paralleldisplaybus/ParallelBus.h"
 #endif
+#include "shared/runtime/interrupt_char.h"
 #include "shared-bindings/microcontroller/Pin.h"
 #include "shared-bindings/time/__init__.h"
 #include "shared-module/displayio/__init__.h"
@@ -73,6 +75,9 @@ void common_hal_busdisplay_busdisplay_construct(busdisplay_busdisplay_obj_t *sel
         uint8_t *data = cmd + 2;
         while (!displayio_display_bus_begin_transaction(&self->bus)) {
             RUN_BACKGROUND_TASKS;
+            if (mp_hal_is_interrupted()) {
+                mp_raise_RuntimeError_varg(MP_ERROR_TEXT("%q init failed"), MP_QSTR_display);
+            }
         }
         if (self->bus.data_as_commands) {
             uint8_t full_command[data_size + 1];
@@ -288,11 +293,9 @@ static bool _refresh_area(busdisplay_busdisplay_obj_t *self, const displayio_are
         displayio_display_core_fill_area(&self->core, &subrectangle, mask, buffer);
 
         // Can't acquire display bus; skip the rest of the data.
-        if (!displayio_display_bus_is_free(&self->bus)) {
+        if (!displayio_display_bus_begin_transaction(&self->bus)) {
             return false;
         }
-
-        displayio_display_bus_begin_transaction(&self->bus);
         _send_pixels(self, (uint8_t *)buffer, subrectangle_size_bytes);
         displayio_display_bus_end_transaction(&self->bus);
 

shared-module/displayio/bus_core.c

@@ -85,11 +85,16 @@ void displayio_display_bus_construct(displayio_display_bus_t *self,
     self->bus = bus;
 }
 
+// This is just a hint, and is not a reliable result, since the bus could be grabbed in between this called
+// and the attempt to use the bus. Use displayio_display_bus_begin_transaction(), which is atomic.
 bool displayio_display_bus_is_free(displayio_display_bus_t *self) {
     return !self->bus || self->bus_free(self->bus);
 }
 
-bool displayio_display_bus_begin_transaction(displayio_display_bus_t *self) {
+MP_WARN_UNUSED_RESULT bool displayio_display_bus_begin_transaction(displayio_display_bus_t *self) {
+    if (!self->bus) {
+        return false;
+    }
     mp_obj_base_t *bus_base = MP_OBJ_TO_PTR(self->bus);
     if (bus_base->type == &mp_type_NoneType) {
         return false;
@@ -128,7 +133,9 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
     }
 
     // Set column.
-    displayio_display_bus_begin_transaction(self);
+    if (!displayio_display_bus_begin_transaction(self)) {
+        return;
+    }
     uint8_t data[5];
     data[0] = self->column_command;
     uint8_t data_length = 1;
@@ -167,7 +174,9 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
 
     if (self->set_current_column_command != NO_COMMAND) {
         uint8_t command = self->set_current_column_command;
-        displayio_display_bus_begin_transaction(self);
+        if (!displayio_display_bus_begin_transaction(self)) {
+            return;
+        }
         self->send(self->bus, DISPLAY_COMMAND, chip_select, &command, 1);
         // Only send the first half of data because it is the first coordinate.
         self->send(self->bus, DISPLAY_DATA, chip_select, data, data_length / 2);
@@ -176,7 +185,9 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
 
 
     // Set row.
-    displayio_display_bus_begin_transaction(self);
+    if (!displayio_display_bus_begin_transaction(self)) {
+        return;
+    }
     data[0] = self->row_command;
     data_length = 1;
     if (!self->data_as_commands) {
@@ -211,7 +222,9 @@ void displayio_display_bus_set_region_to_update(displayio_display_bus_t *self, d
 
     if (self->set_current_row_command != NO_COMMAND) {
         uint8_t command = self->set_current_row_command;
-        displayio_display_bus_begin_transaction(self);
+        if (!displayio_display_bus_begin_transaction(self)) {
+            return;
+        }
         self->send(self->bus, DISPLAY_COMMAND, chip_select, &command, 1);
         // Only send the first half of data because it is the first coordinate.
         self->send(self->bus, DISPLAY_DATA, chip_select, data, data_length / 2);

shared-module/epaperdisplay/EPaperDisplay.c

@@ -153,7 +153,10 @@ static void send_command_sequence(epaperdisplay_epaperdisplay_obj_t *self,
             data_size = ((data_size & ~DELAY) << 8) + *(cmd + 2);
             data = cmd + 3;
         }
-        displayio_display_bus_begin_transaction(&self->bus);
+        while (!displayio_display_bus_begin_transaction(&self->bus) &&
+               !mp_hal_is_interrupted()) {
+            RUN_BACKGROUND_TASKS;
+        }
         self->bus.send(self->bus.bus, DISPLAY_COMMAND, self->chip_select, cmd, 1);
         self->bus.send(self->bus.bus, DISPLAY_DATA, self->chip_select, data, data_size);
         displayio_display_bus_end_transaction(&self->bus);
@@ -311,7 +314,10 @@ static bool epaperdisplay_epaperdisplay_refresh_area(epaperdisplay_epaperdisplay
         if (pass == 1) {
             write_command = self->write_color_ram_command;
         }
-        displayio_display_bus_begin_transaction(&self->bus);
+        if (!displayio_display_bus_begin_transaction(&self->bus)) {
+            // Display bus not available now.
+            return false;
+        }
         self->bus.send(self->bus.bus, DISPLAY_COMMAND, self->chip_select, &write_command, 1);
         displayio_display_bus_end_transaction(&self->bus);
 
@@ -388,7 +394,9 @@ static bool _clean_area(epaperdisplay_epaperdisplay_obj_t *self) {
     memset(buffer, 0x77, width / 2);
 
     uint8_t write_command = self->write_black_ram_command;
-    displayio_display_bus_begin_transaction(&self->bus);
+    if (displayio_display_bus_begin_transaction(&self->bus)) {
+        return false;
+    }
     self->bus.send(self->bus.bus, DISPLAY_COMMAND, self->chip_select, &write_command, 1);
     displayio_display_bus_end_transaction(&self->bus);