displayio: implement, use allocate_display_or_raise

shared-bindings/displayio/Display.c

@@ -152,17 +152,8 @@ STATIC mp_obj_t displayio_display_make_new(const mp_obj_type_t *type, size_t n_a
         mp_raise_ValueError(translate("Display rotation must be in 90 degree increments"));
     }
 
-    displayio_display_obj_t *self = NULL;
-    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
-        if (displays[i].display.base.type == NULL ||
-            displays[i].display.base.type == &mp_type_NoneType) {
-            self = &displays[i].display;
-            break;
-        }
-    }
-    if (self == NULL) {
-        mp_raise_RuntimeError(translate("Too many displays"));
-    }
+    primary_display_t *disp = allocate_display_or_raise();
+    displayio_display_obj_t *self = &disp->display;;
     self->base.type = &displayio_display_type;
     common_hal_displayio_display_construct(
         self,

shared-bindings/displayio/EPaperDisplay.c

@@ -136,17 +136,8 @@ STATIC mp_obj_t displayio_epaperdisplay_make_new(const mp_obj_type_t *type, size
         mp_raise_ValueError(translate("Display rotation must be in 90 degree increments"));
     }
 
-    displayio_epaperdisplay_obj_t *self = NULL;
-    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
-        if (displays[i].display.base.type == NULL ||
-            displays[i].display.base.type == &mp_type_NoneType) {
-            self = &displays[i].epaper_display;
-            break;
-        }
-    }
-    if (self == NULL) {
-        mp_raise_RuntimeError(translate("Too many displays"));
-    }
+    primary_display_t *disp = allocate_display_or_raise();
+    displayio_epaperdisplay_obj_t *self = &disp->epaper_display;;
 
     mp_float_t refresh_time = mp_obj_get_float(args[ARG_refresh_time].u_obj);
     mp_float_t seconds_per_frame = mp_obj_get_float(args[ARG_seconds_per_frame].u_obj);

shared-module/displayio/__init__.c

@@ -308,3 +308,21 @@ void displayio_area_transform_within(bool mirror_x, bool mirror_y, bool transpos
         transformed->x1 = whole->x1 + (y1 - whole->y1);
     }
 }
+
+primary_display_t *allocate_display() {
+    for (uint8_t i = 0; i < CIRCUITPY_DISPLAY_LIMIT; i++) {
+        mp_const_obj_t display_type = displays[i].display.base.type;
+        if (display_type == NULL || display_type == &mp_type_NoneType) {
+            return &displays[i];
+        }
+    }
+    return NULL;
+
+primary_display_t *allocate_display_or_raise() {
+    primary_display_t *result = allocate_display();
+    if (!result) {
+        mp_raise_RuntimeError(translate("Too many displays"));
+    }
+}
+
+}

shared-module/displayio/__init__.h

@@ -54,4 +54,7 @@ void displayio_background(void);
 void reset_displays(void);
 void displayio_gc_collect(void);
 
+primary_display_t *allocate_display(void);
+primary_display_t *allocate_display_or_raise(void);
+
 #endif // MICROPY_INCLUDED_SHARED_MODULE_DISPLAYIO___INIT___H