examples/hotplugtest: Allow multiple devices attaching

If no device ID is specified, and for instance a hub is plugged, many
devices will be attached (and later detached) at the same time. The old
code counting only 2 events would then exit prematurely.

By counting attach and detach events separately, we preserve the old
behaviour in the single-device case, but also allow more complex
sequences to be handled in a way that mostly appears intuitive.

This is not fool-proof, and we can still end up leaving after a surprise
detachment of a "pre-existing" device while we have one of the "new"
devices open. In this case print a warning.

References libusb#1455

Signed-off-by: Tormod Volden <[email protected]>

examples/hotplugtest.c

@@ -23,7 +23,8 @@
 
 #include "libusb.h"
 
-int done = 0;
+int done_attach = 0;
+int done_detach = 0;
 libusb_device_handle *handle = NULL;
 
 static int LIBUSB_CALL hotplug_callback(libusb_context *ctx, libusb_device *dev, libusb_hotplug_event event, void *user_data)
@@ -56,7 +57,7 @@ static int LIBUSB_CALL hotplug_callback(libusb_context *ctx, libusb_device *dev,
 			 libusb_strerror((enum libusb_error)rc));
 	}
 
-	done++;
+	done_attach++;
 
 	return 0;
 }
@@ -85,7 +86,7 @@ static int LIBUSB_CALL hotplug_callback_detach(libusb_context *ctx, libusb_devic
 		handle = NULL;
 	}
 
-	done++;
+	done_detach++;
 
 	return 0;
 }
@@ -130,14 +131,15 @@ int main(int argc, char *argv[])
 		return EXIT_FAILURE;
 	}
 
-	while (done < 2) {
+	while (done_detach < done_attach || done_attach == 0) {
 		rc = libusb_handle_events (NULL);
 		if (LIBUSB_SUCCESS != rc)
 			printf ("libusb_handle_events() failed: %s\n",
 				libusb_strerror((enum libusb_error)rc));
 	}
 
 	if (handle) {
+		printf ("Warning: Closing left-over open handle\n");
 		libusb_close (handle);
 	}