thunderbolt: Make tb_switch_alloc() return ERR_PTR()

In order to detect possible connections to other domains we need to be
able to find out why tb_switch_alloc() fails so make it return ERR_PTR()
instead. This allows the caller to differentiate between errors such as
-ENOMEM which comes from the kernel and for instance -EIO which comes
from the hardware when trying to access the possible switch.

Convert all the current call sites to handle this properly.

Signed-off-by: Mika Westerberg <[e-mail]>

drivers/thunderbolt/icm.c

···
 	pm_runtime_get_sync(&parent_sw->dev);
 
 	sw = tb_switch_alloc(parent_sw->tb, &parent_sw->dev, route);
-	if (!sw)
+	if (IS_ERR(sw))
 		goto out;
 
 	sw->uuid = kmemdup(uuid, sizeof(*uuid), GFP_KERNEL);
···
 		tb->root_switch = tb_switch_alloc_safe_mode(tb, &tb->dev, 0);
 	else
 		tb->root_switch = tb_switch_alloc(tb, &tb->dev, 0);
-	if (!tb->root_switch)
-		return -ENODEV;
+	if (IS_ERR(tb->root_switch))
+		return PTR_ERR(tb->root_switch);
 
 	/*
 	 * NVM upgrade has not been tested on Apple systems and they

drivers/thunderbolt/switch.c

···
  * separately. The returned switch should be released by calling
  * tb_switch_put().
  *
- * Return: Pointer to the allocated switch or %NULL in case of failure
+ * Return: Pointer to the allocated switch or ERR_PTR() in case of
+ * failure.
  */
 struct tb_switch *tb_switch_alloc(struct tb *tb, struct device *parent,
 				  u64 route)
 {
 	struct tb_switch *sw;
 	int upstream_port;
-	int i, cap, depth;
+	int i, ret, depth;
 
 	/* Make sure we do not exceed maximum topology limit */
 	depth = tb_route_length(route);
 	if (depth > TB_SWITCH_MAX_DEPTH)
-		return NULL;
+		return ERR_PTR(-EADDRNOTAVAIL);
 
 	upstream_port = tb_cfg_get_upstream_port(tb->ctl, route);
 	if (upstream_port < 0)
-		return NULL;
+		return ERR_PTR(upstream_port);
 
 	sw = kzalloc(sizeof(*sw), GFP_KERNEL);
 	if (!sw)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	sw->tb = tb;
-	if (tb_cfg_read(tb->ctl, &sw->config, route, 0, TB_CFG_SWITCH, 0, 5))
+	ret = tb_cfg_read(tb->ctl, &sw->config, route, 0, TB_CFG_SWITCH, 0, 5);
+	if (ret)
 		goto err_free_sw_ports;
 
 	tb_dbg(tb, "current switch config:\n");
···
 	/* initialize ports */
 	sw->ports = kcalloc(sw->config.max_port_number + 1, sizeof(*sw->ports),
 				GFP_KERNEL);
-	if (!sw->ports)
+	if (!sw->ports) {
+		ret = -ENOMEM;
 		goto err_free_sw_ports;
+	}
 
 	for (i = 0; i <= sw->config.max_port_number; i++) {
 		/* minimum setup for tb_find_cap and tb_drom_read to work */
···
 
 	sw->generation = tb_switch_get_generation(sw);
 
-	cap = tb_switch_find_vse_cap(sw, TB_VSE_CAP_PLUG_EVENTS);
-	if (cap < 0) {
+	ret = tb_switch_find_vse_cap(sw, TB_VSE_CAP_PLUG_EVENTS);
+	if (ret < 0) {
 		tb_sw_warn(sw, "cannot find TB_VSE_CAP_PLUG_EVENTS aborting\n");
 		goto err_free_sw_ports;
 	}
-	sw->cap_plug_events = cap;
+	sw->cap_plug_events = ret;
 
-	cap = tb_switch_find_vse_cap(sw, TB_VSE_CAP_LINK_CONTROLLER);
-	if (cap > 0)
-		sw->cap_lc = cap;
+	ret = tb_switch_find_vse_cap(sw, TB_VSE_CAP_LINK_CONTROLLER);
+	if (ret > 0)
+		sw->cap_lc = ret;
 
 	/* Root switch is always authorized */
 	if (!route)
···
 	kfree(sw->ports);
 	kfree(sw);
 
-	return NULL;
+	return ERR_PTR(ret);
 }
 
 /**
···
  *
  * The returned switch must be released by calling tb_switch_put().
  *
- * Return: Pointer to the allocated switch or %NULL in case of failure
+ * Return: Pointer to the allocated switch or ERR_PTR() in case of failure
  */
 struct tb_switch *
 tb_switch_alloc_safe_mode(struct tb *tb, struct device *parent, u64 route)
···
 
 	sw = kzalloc(sizeof(*sw), GFP_KERNEL);
 	if (!sw)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	sw->tb = tb;
 	sw->config.depth = tb_route_length(route);

drivers/thunderbolt/tb.c

···
 	}
 	sw = tb_switch_alloc(port->sw->tb, &port->sw->dev,
 			     tb_downstream_route(port));
-	if (!sw)
+	if (IS_ERR(sw))
 		return;
 
 	if (tb_switch_configure(sw)) {
···
 	int ret;
 
 	tb->root_switch = tb_switch_alloc(tb, &tb->dev, 0);
-	if (!tb->root_switch)
-		return -ENOMEM;
+	if (IS_ERR(tb->root_switch))
+		return PTR_ERR(tb->root_switch);
 
 	/*
 	 * ICM firmware upgrade needs running firmware and in native