applications: nrf_desktop: Improve HID subscription in USB state

Change ensures that the module would unsubscribe from previously used
HID protocol mode before subscribing for the new HID protocol mode.
This ensures that HID boot and HID report protocol mode subscriptions
are not enabled at the same time.

Jira: NCSDK-34349

Signed-off-by: Marek Pieta <[email protected]>

Author: MarekPieta

applications/nrf_desktop/src/modules/usb_state.c

@@ -534,7 +534,8 @@ static void broadcast_subscriber_change(struct usb_hid_device *usb_hid)
 	APP_EVENT_SUBMIT(event);
 }
 
-static void broadcast_subscription_change(struct usb_hid_device *usb_hid)
+static void broadcast_subscription_change_internal(struct usb_hid_device *usb_hid,
+						   bool enabled_filter)
 {
 	bool new_rep_enabled = (usb_hid->enabled) && (usb_hid->hid_protocol == HID_PROTOCOL_REPORT);
 	bool new_boot_enabled = (usb_hid->enabled) && (usb_hid->hid_protocol == HID_PROTOCOL_BOOT);
@@ -543,6 +544,10 @@ static void broadcast_subscription_change(struct usb_hid_device *usb_hid)
 		uint8_t rep_id = input_reports[i];
 		bool new_enabled = is_hid_boot_report(rep_id) ? new_boot_enabled : new_rep_enabled;
 
+		if (new_enabled != enabled_filter) {
+			continue;
+		}
+
 		if ((new_enabled != usb_hid->report_enabled[rep_id]) &&
 		    (usb_hid->report_bm & BIT(rep_id))) {
 			struct hid_report_subscription_event *event =
@@ -557,6 +562,15 @@ static void broadcast_subscription_change(struct usb_hid_device *usb_hid)
 			usb_hid->report_enabled[rep_id] = new_enabled;
 		}
 	}
+}
+
+static void broadcast_subscription_change(struct usb_hid_device *usb_hid)
+{
+	/* First disable old subscriptions, then enable new subscriptions. This is done to ensure
+	 * that HID boot and HID report mode subscriptions would never be enabled at the same time.
+	 */
+	broadcast_subscription_change_internal(usb_hid, false);
+	broadcast_subscription_change_internal(usb_hid, true);
 
 	LOG_INF("USB HID %p %sabled", (void *)usb_hid, (usb_hid->enabled) ? ("en"):("dis"));
 	if (usb_hid->enabled) {