Basic support for multiple Hailo models

This allows multiple models to be loaded and used through separate
Hailo objects. They should be used in serial in the same thread,
however, as there is no other locking applied.

Signed-off-by: David Plowman <[email protected]>

picamera2/devices/hailo/hailo.py

@@ -6,6 +6,9 @@
 
 
 class Hailo:
+    TARGET = None
+    TARGET_REF_COUNT = 0
+
     def __init__(self, hef_path, batch_size=None, output_type='FLOAT32'):
         """
         Initialize the HailoAsyncInference class with the provided HEF model file path.
@@ -20,7 +23,10 @@ def __init__(self, hef_path, batch_size=None, output_type='FLOAT32'):
 
         self.batch_size = batch_size
         self.hef = HEF(hef_path)
-        self.target = VDevice(params)
+        if Hailo.TARGET is None:
+            Hailo.TARGET = VDevice(params)
+            Hailo.TARGET_REF_COUNT += 1
+        self.target = Hailo.TARGET
         self.infer_model = self.target.create_infer_model(hef_path)
         self.infer_model.set_batch_size(1 if batch_size is None else batch_size)
         self._set_input_output(output_type)
@@ -175,4 +181,6 @@ def _create_bindings(self):
     def close(self):
         """Release the Hailo device."""
         del self.configured_infer_model
-        self.target.release()
+        Hailo.TARGET_REF_COUNT -= 1
+        if Hailo.TARGET_REF_COUNT == 0:
+            self.target.release()