[PATCHv2] thunderbolt: tunnel: simplify allocation

[Rosen Penev <rosenp@gmail.com>]

Use a flexible array member and kzalloc_flex to combine allocations.

Add __counted_by for extra runtime analysis. Move counting variable
assignment after allocation. kzalloc_flex with GCC >= 15 does this
automatically.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 v2: move kernel-doc and reword slightly.
 drivers/thunderbolt/tunnel.c | 10 ++--------
 drivers/thunderbolt/tunnel.h |  5 +++--
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 89676acf1290..f38f7753b6e4 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -180,19 +180,14 @@ static struct tb_tunnel *tb_tunnel_alloc(struct tb *tb, size_t npaths,
 {
 	struct tb_tunnel *tunnel;

-	tunnel = kzalloc_obj(*tunnel);
+	tunnel = kzalloc_flex(*tunnel, paths, npaths);
 	if (!tunnel)
 		return NULL;

-	tunnel->paths = kzalloc_objs(tunnel->paths[0], npaths);
-	if (!tunnel->paths) {
-		kfree(tunnel);
-		return NULL;
-	}
+	tunnel->npaths = npaths;

 	INIT_LIST_HEAD(&tunnel->list);
 	tunnel->tb = tb;
-	tunnel->npaths = npaths;
 	tunnel->type = type;
 	kref_init(&tunnel->kref);

@@ -219,7 +214,6 @@ static void tb_tunnel_destroy(struct kref *kref)
 			tb_path_free(tunnel->paths[i]);
 	}

-	kfree(tunnel->paths);
 	kfree(tunnel);
 }

diff --git a/drivers/thunderbolt/tunnel.h b/drivers/thunderbolt/tunnel.h
index 2c44fc8a10bc..4878763a82b3 100644
--- a/drivers/thunderbolt/tunnel.h
+++ b/drivers/thunderbolt/tunnel.h
@@ -37,7 +37,6 @@ enum tb_tunnel_state {
  * @src_port: Source port of the tunnel
  * @dst_port: Destination port of the tunnel. For discovered incomplete
  *	      tunnels may be %NULL or null adapter port instead.
- * @paths: All paths required by the tunnel
  * @npaths: Number of paths in @paths
  * @pre_activate: Optional tunnel specific initialization called before
  *		  activation. Can touch hardware.
@@ -69,13 +68,13 @@ enum tb_tunnel_state {
  * @dprx_work: Worker that is scheduled to poll completion of DPRX capabilities read
  * @callback: Optional callback called when DP tunnel is fully activated
  * @callback_data: Optional data for @callback
+ * @paths: All paths required by the tunnel
  */
 struct tb_tunnel {
 	struct kref kref;
 	struct tb *tb;
 	struct tb_port *src_port;
 	struct tb_port *dst_port;
-	struct tb_path **paths;
 	size_t npaths;
 	int (*pre_activate)(struct tb_tunnel *tunnel);
 	int (*activate)(struct tb_tunnel *tunnel, bool activate);
@@ -107,6 +106,8 @@ struct tb_tunnel {
 	struct delayed_work dprx_work;
 	void (*callback)(struct tb_tunnel *tunnel, void *data);
 	void *callback_data;
+
+	struct tb_path *paths[] __counted_by(npaths);
 };

 struct tb_tunnel *tb_tunnel_discover_pci(struct tb *tb, struct tb_port *down,
--
2.53.0