Tests: USBHID: Handle variable driver setup time

Wait for the host driver to finish setup before sending any HID reports
from the device.

USBHID::wait_ready() blocks until the device reaches 'configured' state,
but the state of the host HID driver remains unknown to the device.

TESTS/host_tests/usb_device_hid.py

@@ -69,7 +69,8 @@ HID_PROTOCOL_KEYBOARD = 1
 HID_PROTOCOL_MOUSE = 2
 
 # Greentea message keys used for callbacks
-MSG_KEY_DEVICE_READY = 'ready'
+MSG_KEY_DEVICE_READY = 'dev_ready'
+MSG_KEY_HOST_READY = 'host_ready'
 MSG_KEY_SERIAL_NUMBER = 'usb_dev_sn'
 MSG_KEY_TEST_GET_DESCRIPTOR_HID = 'test_get_desc_hid'
 MSG_KEY_TEST_GET_DESCRIPTOR_CFG = 'test_get_desc_cfg'
@@ -495,6 +496,8 @@ class USBHIDTest(mbed_host_tests.BaseHostTest):
         except RetryError as exc:
             self.notify_error(exc)
             return
+        # Notify the device it can send reports now.
+        self.send_kv(MSG_KEY_HOST_READY, MSG_VALUE_DUMMY)
         try:
             for _ in range(RAW_IO_REPS):
                 # There are no Report ID tags in the Report descriptor.

TESTS/usb_device/hid/main.cpp

@@ -38,6 +38,8 @@
 #define MSG_VALUE_LEN 24
 #define MSG_KEY_LEN 24
 #define MSG_KEY_DEVICE_READY "ready"
+#define MSG_KEY_DEVICE_READY "dev_ready"
+#define MSG_KEY_HOST_READY "host_ready"
 #define MSG_KEY_SERIAL_NUMBER "usb_dev_sn"
 #define MSG_KEY_TEST_GET_DESCRIPTOR_HID "test_get_desc_hid"
 #define MSG_KEY_TEST_GET_DESCRIPTOR_CFG "test_get_desc_cfg"
@@ -307,6 +309,12 @@ void test_generic_raw_io()
     greentea_send_kv(MSG_KEY_TEST_RAW_IO, REPORT_SIZE);
     usb_hid.wait_ready();
 
+    // Wait for the host HID driver to complete setup.
+    char key[MSG_KEY_LEN + 1] = { };
+    char value[MSG_VALUE_LEN + 1] = { };
+    greentea_parse_kv(key, value, MSG_KEY_LEN, MSG_VALUE_LEN);
+    TEST_ASSERT_EQUAL_STRING(MSG_KEY_HOST_READY, key);
+
     // Report ID omitted here. There are no Report ID tags in the Report descriptor.
     HID_REPORT input_report = {};
     HID_REPORT output_report = {};