pybricks/tools/awaitable: Add raise on busy option.

Until we work out clever ways of cancellation or queueing, we can
prevent certain resources from being used on more than one task at all.

Author: laurensvalk

pybricks/common/pb_type_speaker.c

@@ -172,7 +172,7 @@ STATIC mp_obj_t pb_type_Speaker_beep(size_t n_args, const mp_obj_t *pos_args, mp
         pb_type_Speaker_beep_test_completion,
         pb_type_awaitable_return_none,
         pb_type_Speaker_cancel,
-        PB_TYPE_AWAITABLE_OPT_CANCEL_ALL | PB_TYPE_AWAITABLE_OPT_CANCEL_HARDWARE);
+        PB_TYPE_AWAITABLE_OPT_RAISE_ON_BUSY);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pb_type_Speaker_beep_obj, 1, pb_type_Speaker_beep);
 
@@ -388,7 +388,7 @@ STATIC mp_obj_t pb_type_Speaker_play_notes(size_t n_args, const mp_obj_t *pos_ar
         pb_type_Speaker_notes_test_completion,
         pb_type_awaitable_return_none,
         pb_type_Speaker_cancel,
-        PB_TYPE_AWAITABLE_OPT_CANCEL_ALL | PB_TYPE_AWAITABLE_OPT_CANCEL_HARDWARE);
+        PB_TYPE_AWAITABLE_OPT_RAISE_ON_BUSY);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pb_type_Speaker_play_notes_obj, 1, pb_type_Speaker_play_notes);
 

pybricks/pupdevices/pb_module_pupdevices.c

@@ -96,7 +96,7 @@ mp_obj_t pb_pupdevices_set_data(pb_pupdevices_obj_base_t *sensor, uint8_t mode,
         pb_pup_device_test_completion,
         pb_type_awaitable_return_none,
         pb_type_awaitable_cancel_none,
-        PB_TYPE_AWAITABLE_OPT_NONE); // choose opt raise on busy
+        PB_TYPE_AWAITABLE_OPT_RAISE_ON_BUSY);
 }
 
 void pb_pupdevices_init_class(pb_pupdevices_obj_base_t *self, mp_obj_t port_in, pbio_iodev_type_id_t valid_id) {

pybricks/tools/pb_type_awaitable.c

@@ -148,18 +148,27 @@ void pb_type_awaitable_update_all(mp_obj_t awaitables_in, pb_type_awaitable_opt_
 
     for (size_t i = 0; i < awaitables->len; i++) {
         pb_type_awaitable_obj_t *awaitable = MP_OBJ_TO_PTR(awaitables->items[i]);
-        // Only cancel awaitables that are in use.
-        if (awaitable->test_completion) {
-            // Cancel hardware operation if requested and available.
-            if (options & PB_TYPE_AWAITABLE_OPT_CANCEL_HARDWARE && awaitable->cancel) {
-                awaitable->cancel(awaitable->obj);
-            }
-            // Set awaitable to done so it gets cancelled it gracefully on the
-            // next iteration.
-            if (options & PB_TYPE_AWAITABLE_OPT_CANCEL_ALL) {
-                awaitable->test_completion = pb_type_awaitable_completed;
-            }
+
+        // Skip awaitables that are not in use.
+        if (!awaitable->test_completion) {
+            continue;
+        }
+
+        // Raise EBUSY if requested.
+        if (options & PB_TYPE_AWAITABLE_OPT_RAISE_ON_BUSY) {
+            mp_raise_msg(&mp_type_OSError, MP_ERROR_TEXT("This resource cannot be used in two tasks at once."));
         }
+
+        // Cancel hardware operation if requested and available.
+        if (options & PB_TYPE_AWAITABLE_OPT_CANCEL_HARDWARE && awaitable->cancel) {
+            awaitable->cancel(awaitable->obj);
+        }
+        // Set awaitable to done so it gets cancelled it gracefully on the
+        // next iteration.
+        if (options & PB_TYPE_AWAITABLE_OPT_CANCEL_ALL) {
+            awaitable->test_completion = pb_type_awaitable_completed;
+        }
+
     }
 }
 

pybricks/tools/pb_type_awaitable.h

@@ -34,6 +34,11 @@ typedef enum _pb_type_awaitable_opt_t {
      * already cleaned up by lower level drivers (so not needed for motors).
      */
     PB_TYPE_AWAITABLE_OPT_CANCEL_HARDWARE  = 1 << 3,
+    /**
+     * Raises EBUSY if the resource is already in use. Used for resources that
+     * do not support graceful cancellation.
+     */
+    PB_TYPE_AWAITABLE_OPT_RAISE_ON_BUSY = 1 << 4,
 } pb_type_awaitable_opt_t;
 
 /**