applications: nrf_desktop: Improve HID subscription in HIDS

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/hids.c

@@ -76,14 +76,20 @@ static bool protocol_boot;
 static struct config_channel_transport cfg_chan_transport;
 static struct k_work_delayable notify_secured;
 
-static void broadcast_subscription_change(uint8_t report_id, bool enabled)
+
+static bool is_hid_boot_report(uint8_t report_id)
 {
-	bool boot = (report_id == REPORT_ID_BOOT_MOUSE) ||
-		    (report_id == REPORT_ID_BOOT_KEYBOARD);
+	return (report_id == REPORT_ID_BOOT_MOUSE) || (report_id == REPORT_ID_BOOT_KEYBOARD);
+}
 
-	enabled = enabled && (protocol_boot == boot);
+static bool is_subscribed(uint8_t report_id)
+{
+	return report_enabled[report_id] && (protocol_boot == is_hid_boot_report(report_id));
+}
 
-	if (enabled == subscribed[report_id]) {
+static void broadcast_subscription_change(uint8_t report_id, bool subscribe)
+{
+	if (subscribe == subscribed[report_id]) {
 		/* No change in subscription. */
 		return;
 	}
@@ -93,13 +99,13 @@ static void broadcast_subscription_change(uint8_t report_id, bool enabled)
 		return;
 	}
 
-	subscribed[report_id] = enabled;
+	subscribed[report_id] = subscribe;
 
 	struct hid_report_subscription_event *event =
 		new_hid_report_subscription_event();
 
 	event->report_id  = report_id;
-	event->enabled    = enabled;
+	event->enabled    = subscribe;
 	event->subscriber = cur_conn;
 
 	LOG_INF("Notifications for report 0x%x are %sabled", report_id,
@@ -108,6 +114,24 @@ static void broadcast_subscription_change(uint8_t report_id, bool enabled)
 	APP_EVENT_SUBMIT(event);
 }
 
+static void broadcast_all_subscription_changes_internal(bool subscribed_filter)
+{
+	for (size_t r_id = 0; r_id < REPORT_ID_COUNT; r_id++) {
+		if (is_subscribed(r_id) == subscribed_filter) {
+			broadcast_subscription_change(r_id, subscribed_filter);
+		}
+	}
+}
+
+static void broadcast_all_subscription_changes(void)
+{
+	/* 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_all_subscription_changes_internal(false);
+	broadcast_all_subscription_changes_internal(true);
+}
+
 static void pm_evt_handler(enum bt_hids_pm_evt evt, struct bt_conn *conn)
 {
 	switch (evt) {
@@ -125,10 +149,7 @@ static void pm_evt_handler(enum bt_hids_pm_evt evt, struct bt_conn *conn)
 		break;
 	}
 
-	for (size_t r_id = 0; r_id < REPORT_ID_COUNT; r_id++) {
-		bool enabled = report_enabled[r_id];
-		broadcast_subscription_change(r_id, enabled);
-	}
+	broadcast_all_subscription_changes();
 }
 
 static void sync_notif_handler(const struct hid_notification_event *event)
@@ -145,7 +166,7 @@ static void sync_notif_handler(const struct hid_notification_event *event)
 
 	report_enabled[report_id] = enabled;
 
-	broadcast_subscription_change(report_id, enabled);
+	broadcast_subscription_change(report_id, is_subscribed(report_id));
 }
 
 static void notification_change_handler_async(uint8_t report_id, enum bt_hids_notify_evt evt)
@@ -504,11 +525,7 @@ static void send_hid_report(const struct hid_report_event *event)
 static void notify_secured_fn(struct k_work *work)
 {
 	secured = true;
-
-	for (size_t r_id = 0; r_id < REPORT_ID_COUNT; r_id++) {
-		bool enabled = report_enabled[r_id];
-		broadcast_subscription_change(r_id, enabled);
-	}
+	broadcast_all_subscription_changes();
 }
 
 static void broadcast_hids_subscriber_state(void *subscriber, bool enabled)