thunderbolt: Allow disabling XDomain protocol

This allows disabling XDomain protocol completely if the user does not
plan to use the USB4/Thunderbolt peer-to-peer functionality, or for
security reasons.

XDomain protocol is enabled by default but with this commit it is
possible to disable it by passing "xdomain=0" as module parameter (or
through the kernel command line).
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Yehezkel Bernat <YehezkelShB@gmail.com>

drivers/thunderbolt/domain.c

@@ -412,7 +412,9 @@ static bool tb_domain_event_cb(void *data, enum tb_cfg_pkg_type type,
 	switch (type) {
 	case TB_CFG_PKG_XDOMAIN_REQ:
 	case TB_CFG_PKG_XDOMAIN_RESP:
-		return tb_xdomain_handle_request(tb, type, buf, size);
+		if (tb_is_xdomain_enabled())
+			return tb_xdomain_handle_request(tb, type, buf, size);
+		break;
 
 	default:
 		tb->cm_ops->handle_event(tb, type, buf, size);

drivers/thunderbolt/icm.c

@@ -1701,10 +1701,12 @@ static void icm_handle_notification(struct work_struct *work)
 			icm->device_disconnected(tb, n->pkg);
 			break;
 		case ICM_EVENT_XDOMAIN_CONNECTED:
-			icm->xdomain_connected(tb, n->pkg);
+			if (tb_is_xdomain_enabled())
+				icm->xdomain_connected(tb, n->pkg);
 			break;
 		case ICM_EVENT_XDOMAIN_DISCONNECTED:
-			icm->xdomain_disconnected(tb, n->pkg);
+			if (tb_is_xdomain_enabled())
+				icm->xdomain_disconnected(tb, n->pkg);
 			break;
 		case ICM_EVENT_RTD3_VETO:
 			icm->rtd3_veto(tb, n->pkg);

drivers/thunderbolt/tb.c

@@ -179,6 +179,9 @@ static void tb_scan_xdomain(struct tb_port *port)
 	struct tb_xdomain *xd;
 	u64 route;
 
+	if (!tb_is_xdomain_enabled())
+		return;
+
 	route = tb_downstream_route(port);
 	xd = tb_xdomain_find_by_route(tb, route);
 	if (xd) {

drivers/thunderbolt/tb.h

@@ -958,6 +958,7 @@ static inline u64 tb_downstream_route(struct tb_port *port)
 	       | ((u64) port->port << (port->sw->config.depth * 8));
 }
 
+bool tb_is_xdomain_enabled(void);
 bool tb_xdomain_handle_request(struct tb *tb, enum tb_cfg_pkg_type type,
 			       const void *buf, size_t size);
 struct tb_xdomain *tb_xdomain_alloc(struct tb *tb, struct device *parent,

drivers/thunderbolt/xdomain.c

@@ -30,6 +30,10 @@ struct xdomain_request_work {
 	struct tb *tb;
 };
 
+static bool tb_xdomain_enabled = true;
+module_param_named(xdomain, tb_xdomain_enabled, bool, 0444);
+MODULE_PARM_DESC(xdomain, "allow XDomain protocol (default: true)");
+
 /* Serializes access to the properties and protocol handlers below */
 static DEFINE_MUTEX(xdomain_lock);
 
@@ -47,6 +51,11 @@ static const uuid_t tb_xdp_uuid =
 	UUID_INIT(0xb638d70e, 0x42ff, 0x40bb,
 		  0x97, 0xc2, 0x90, 0xe2, 0xc0, 0xb2, 0xff, 0x07);
 
+bool tb_is_xdomain_enabled(void)
+{
+	return tb_xdomain_enabled;
+}
+
 static bool tb_xdomain_match(const struct tb_cfg_request *req,
 			     const struct ctl_pkg *pkg)
 {