[PATCH 1/7] thunderbolt: Check for ring 0 in tb_tunnel_alloc_dma()

[Mika Westerberg <mika.westerberg@linux.intel.com>]

Ring 0 cannot be used for anything else than control channel messages.
For this reason add a check to tb_tunnel_alloc_dma() and fail if someone
tries to do that.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/thunderbolt/tunnel.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 9099ae73e78f..dd3b5613ad2c 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -1452,6 +1452,10 @@ struct tb_tunnel *tb_tunnel_alloc_dma(struct tb *tb, struct tb_port *nhi,
 	struct tb_path *path;
 	int credits;
 
+	/* Ring 0 is reserved for control channel */
+	if (WARN_ON(!receive_ring || !transmit_ring))
+		return NULL;
+
 	if (receive_ring > 0)
 		npaths++;
 	if (transmit_ring > 0)
-- 
2.39.2