codal_port/microbit_pinmode: Add microbit_obj_pin_acquire_and_free().

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

src/codal_port/microbit_pinmode.c

@@ -73,6 +73,14 @@ bool microbit_obj_pin_acquire(const microbit_pin_obj_t *pin, const microbit_pinm
     }
 }
 
+void microbit_obj_pin_acquire_and_free(const microbit_pin_obj_t **old_pin, const microbit_pin_obj_t *new_pin, const microbit_pinmode_t *new_mode) {
+    microbit_obj_pin_acquire(new_pin, new_mode);
+    if (*old_pin != new_pin) {
+        microbit_obj_pin_free(*old_pin);
+        *old_pin = new_pin;
+    }
+}
+
 static void noop(const microbit_pin_obj_t *pin) {
     (void)pin;
 }

src/codal_port/modmicrobit.h

@@ -220,6 +220,9 @@ bool microbit_obj_pin_can_be_acquired(const microbit_pin_obj_t *pin);
 // Not safe to call in an interrupt as it may raise if pin can't be acquired.
 bool microbit_obj_pin_acquire(const microbit_pin_obj_t *pin, const microbit_pinmode_t *mode);
 
+// Acquire a new pin and free a previous one, for the given mode.
+void microbit_obj_pin_acquire_and_free(const microbit_pin_obj_t **old_pin, const microbit_pin_obj_t *new_pin, const microbit_pinmode_t *new_mode);
+
 // Change the mode of a pin.  This does not check the existing mode, nor release any
 // resources, and should only be used if pin resources are managed by the caller.
 void microbit_pin_set_mode(const microbit_pin_obj_t *pin, const microbit_pinmode_t *mode);