Report USB device disconnection when detected

USB device disconnection is detected via a hotplug callback when it is
supported.

In addition, report disconnection on libusb calls returning
LIBUSB_ERROR_NO_DEVICE or LIBUSB_ERROR_NOT_FOUND. This allows to detect
disconnection after a libusb call when hotplug is not available.

PR #3011 <https://github.com/Genymobile/scrcpy/pull/3011>

app/src/usb/aoa_hid.c

@@ -95,6 +95,7 @@ sc_aoa_register_hid(struct sc_aoa *aoa, uint16_t accessory_id,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
         LOGE("REGISTER_HID: libusb error: %s", libusb_strerror(result));
+        sc_usb_check_disconnected(aoa->usb, result);
         return false;
     }
 
@@ -131,6 +132,7 @@ sc_aoa_set_hid_report_desc(struct sc_aoa *aoa, uint16_t accessory_id,
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
         LOGE("SET_HID_REPORT_DESC: libusb error: %s", libusb_strerror(result));
+        sc_usb_check_disconnected(aoa->usb, result);
         return false;
     }
 
@@ -173,6 +175,7 @@ sc_aoa_send_hid_event(struct sc_aoa *aoa, const struct sc_hid_event *event) {
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
         LOGE("SEND_HID_EVENT: libusb error: %s", libusb_strerror(result));
+        sc_usb_check_disconnected(aoa->usb, result);
         return false;
     }
 
@@ -195,6 +198,7 @@ sc_aoa_unregister_hid(struct sc_aoa *aoa, const uint16_t accessory_id) {
                                          DEFAULT_TIMEOUT);
     if (result < 0) {
         LOGE("UNREGISTER_HID: libusb error: %s", libusb_strerror(result));
+        sc_usb_check_disconnected(aoa->usb, result);
         return false;
     }
 

app/src/usb/usb.c

@@ -216,6 +216,24 @@ sc_usb_destroy(struct sc_usb *usb) {
     libusb_exit(usb->context);
 }
 
+static void
+sc_usb_report_disconnected(struct sc_usb *usb) {
+    if (usb->cbs && !atomic_flag_test_and_set(&usb->disconnection_notified)) {
+        assert(usb->cbs && usb->cbs->on_disconnected);
+        usb->cbs->on_disconnected(usb, usb->cbs_userdata);
+    }
+}
+
+bool
+sc_usb_check_disconnected(struct sc_usb *usb, int result) {
+    if (result == LIBUSB_ERROR_NO_DEVICE || result == LIBUSB_ERROR_NOT_FOUND) {
+        sc_usb_report_disconnected(usb);
+        return false;
+    }
+
+    return true;
+}
+
 static int
 sc_usb_libusb_callback(libusb_context *ctx, libusb_device *device,
                        libusb_hotplug_event event, void *userdata) {
@@ -232,8 +250,7 @@ sc_usb_libusb_callback(libusb_context *ctx, libusb_device *device,
         return 0;
     }
 
-    assert(usb->cbs && usb->cbs->on_disconnected);
-    usb->cbs->on_disconnected(usb, usb->cbs_userdata);
+    sc_usb_report_disconnected(usb);
 
     // Do not automatically deregister the callback by returning 1. Instead,
     // manually deregister to interrupt libusb_handle_events() from the libusb
@@ -307,6 +324,7 @@ sc_usb_connect(struct sc_usb *usb, libusb_device *device,
 
     if (cbs) {
         atomic_init(&usb->stopped, false);
+        usb->disconnection_notified = (atomic_flag) ATOMIC_FLAG_INIT;
         if (sc_usb_register_callback(usb)) {
             // Create a thread to process libusb events, so that device
             // disconnection could be detected immediately

app/src/usb/usb.h

@@ -22,6 +22,7 @@ struct sc_usb {
     sc_thread libusb_event_thread;
 
     atomic_bool stopped; // only used if cbs != NULL
+    atomic_flag disconnection_notified;
 };
 
 struct sc_usb_callbacks {
@@ -73,6 +74,11 @@ sc_usb_connect(struct sc_usb *usb, libusb_device *device,
 void
 sc_usb_disconnect(struct sc_usb *usb);
 
+// A client should call this function with the return value of a libusb call
+// to detect disconnection immediately
+bool
+sc_usb_check_disconnected(struct sc_usb *usb, int result);
+
 void
 sc_usb_stop(struct sc_usb *usb);