Bluetooth: controller: Fix memory alignment of PDU buffer reference

Align the PDU buffer reference in struct node_rx_pdu so that
node rx type specific parameters, like, terminate and sync
lost reason can be accessed without any memory alignment
issues.

Signed-off-by: Vinayak Kariappa Chettimada <[email protected]>

Author: cvinayak

subsys/bluetooth/controller/ll_sw/lll.h

@@ -290,9 +290,16 @@ struct node_rx_hdr {
 	};
 };
 
+/* Template node rx type with memory aligned offset to PDU buffer.
+ * NOTE: offset to memory aligned pdu buffer location is used to reference
+ *       node rx type specific information, like, terminate or sync lost reason
+ *       from a dedicated node rx structure storage location.
+ */
 struct node_rx_pdu {
 	struct node_rx_hdr hdr;
-	uint8_t               pdu[0];
+	union {
+		uint8_t    pdu[0] __aligned(4);
+	};
 };
 
 enum {

subsys/bluetooth/controller/ll_sw/ull_conn_types.h

@@ -159,9 +159,17 @@ struct ll_conn {
 		uint8_t ack;
 		uint8_t reason_own;
 		uint8_t reason_peer;
+		/* node rx type with memory aligned storage for terminate
+		 * reason.
+		 * HCI will reference the value using the pdu member of
+		 * struct node_rx_pdu.
+		 */
 		struct {
 			struct node_rx_hdr hdr;
-			uint8_t reason;
+			union {
+				uint8_t    pdu[0] __aligned(4);
+				uint8_t    reason;
+			};
 		} node_rx;
 	} llcp_terminate;
 

subsys/bluetooth/controller/ll_sw/ull_sync_types.h

@@ -18,9 +18,16 @@ struct ll_sync_set {
 	uint16_t volatile timeout_reload; /* Non-zero when sync established */
 	uint16_t timeout_expire;
 
+	/* node rx type with memory aligned storage for sync lost reason.
+	 * HCI will reference the value using the pdu member of
+	 * struct node_rx_pdu.
+	 */
 	struct {
 		struct node_rx_hdr hdr;
-		uint8_t reason;
+		union {
+			uint8_t    pdu[0] __aligned(4);
+			uint8_t    reason;
+		};
 	} node_rx_lost;
 };