bluetooth: host: LE CS subevent result reassembly

Adds HCI support for LE CS subevent result continue
event and the reassembly logic for the partial results.

When subevent results are completed or the subevent is
aborted, the user callback is invoked with a buffer
pointing to the HCI event buffer, so no copy is done.

When subevent results are incomplete, then a reassembly
buffer is allocated from a fixed sized pool. This buffer
is used for the reassembling of the subevent result
containing all of the step data, which is then passed
to the user via the callback. kconfigs have been added
to set the size and the count of the reassembly buffer.

Signed-off-by: Burak Gorduk <[email protected]>

include/zephyr/bluetooth/conn.h

@@ -548,7 +548,6 @@ enum bt_conn_le_cs_procedure_done_status {
 /** Subevent done status */
 enum bt_conn_le_cs_subevent_done_status {
 	BT_CONN_LE_CS_SUBEVENT_COMPLETE = BT_HCI_LE_CS_SUBEVENT_DONE_STATUS_COMPLETE,
-	BT_CONN_LE_CS_SUBEVENT_INCOMPLETE = BT_HCI_LE_CS_SUBEVENT_DONE_STATUS_PARTIAL,
 	BT_CONN_LE_CS_SUBEVENT_ABORTED = BT_HCI_LE_CS_SUBEVENT_DONE_STATUS_ABORTED,
 };
 
@@ -618,7 +617,19 @@ struct bt_conn_le_cs_subevent_result {
 		int8_t reference_power_level;
 		/** Procedure status. */
 		enum bt_conn_le_cs_procedure_done_status procedure_done_status;
-		/** Subevent status. */
+		/** Subevent status
+		 *
+		 *  For aborted subevents, this will be set to @ref BT_CONN_LE_CS_SUBEVENT_ABORTED
+		 *  and abort_step will contain the step number on which the subevent was aborted.
+		 *  Consider the following example:
+		 *
+		 *  subevent_done_status = @ref BT_CONN_LE_CS_SUBEVENT_ABORTED
+		 *  num_steps_reported = 160
+		 *  abort_step = 100
+		 *
+		 *  this would mean that steps from 0 to 99 are complete and steps from 100 to 159
+		 *  are aborted.
+		 */
 		enum bt_conn_le_cs_subevent_done_status subevent_done_status;
 		/** Abort reason.
 		 *
@@ -640,6 +651,11 @@ struct bt_conn_le_cs_subevent_result {
 		/** Number of CS steps in the subevent.
 		 */
 		uint8_t num_steps_reported;
+		/** Step number, on which the subevent was aborted
+		 *  if subevent_done_status is @ref BT_CONN_LE_CS_SUBEVENT_COMPLETE
+		 *  then abort_step will be unused and set to 255
+		 */
+		uint8_t abort_step;
 	} header;
 	struct net_buf_simple *step_data_buf;
 };

include/zephyr/bluetooth/hci_types.h

@@ -3636,6 +3636,25 @@ struct bt_hci_evt_le_cs_subevent_result {
 	uint8_t steps[];
 } __packed;
 
+#define BT_HCI_EVT_LE_CS_SUBEVENT_RESULT_CONTINUE 0x32
+
+struct bt_hci_evt_le_cs_subevent_result_continue {
+	uint16_t conn_handle;
+	uint8_t config_id;
+	uint8_t procedure_done_status;
+	uint8_t subevent_done_status;
+#ifdef CONFIG_LITTLE_ENDIAN
+	uint8_t procedure_abort_reason: 4;
+	uint8_t subevent_abort_reason: 4;
+#else
+	uint8_t subevent_abort_reason: 4;
+	uint8_t procedure_abort_reason: 4;
+#endif /* CONFIG_LITTLE_ENDIAN */
+	uint8_t num_antenna_paths;
+	uint8_t num_steps_reported;
+	uint8_t steps[];
+} __packed;
+
 #define BT_HCI_EVT_LE_CS_TEST_END_COMPLETE 0x33
 struct bt_hci_evt_le_cs_test_end_complete {
 	uint8_t status;
@@ -3734,6 +3753,7 @@ struct bt_hci_evt_le_cs_test_end_complete {
 #define BT_EVT_MASK_LE_CS_READ_REMOTE_FAE_TABLE_COMPLETE              BT_EVT_BIT(44)
 #define BT_EVT_MASK_LE_CS_CONFIG_COMPLETE                             BT_EVT_BIT(46)
 #define BT_EVT_MASK_LE_CS_SUBEVENT_RESULT                             BT_EVT_BIT(48)
+#define BT_EVT_MASK_LE_CS_SUBEVENT_RESULT_CONTINUE                    BT_EVT_BIT(49)
 #define BT_EVT_MASK_LE_CS_TEST_END_COMPLETE                           BT_EVT_BIT(50)
 
 /** HCI Error Codes, BT Core Spec v5.4 [Vol 1, Part F]. */

subsys/bluetooth/Kconfig

@@ -203,6 +203,26 @@ config BT_CHANNEL_SOUNDING_TEST
 	help
 	  Enable support for Channel Sounding test mode.
 
+config BT_CHANNEL_SOUNDING_REASSEMBLY_BUFFER_SIZE
+	int "Subevent result reassembly buffer size"
+	depends on BT_CHANNEL_SOUNDING
+	range 239 5600
+	default 5600
+	help
+	  When the results for a CS subevent cannot fit into a single HCI event,
+	  it will be split up into multiple events and consequently, reassembled into a
+	  full CS subevent. This config sets the size of the reassembly buffer.
+
+config BT_CHANNEL_SOUNDING_REASSEMBLY_BUFFER_CNT
+	int "Subevent result reassembly buffer count"
+	depends on BT_CHANNEL_SOUNDING
+	range 1 BT_MAX_CONN
+	default 1
+	help
+	  Controls the number of the reassembly buffers for CS subevent
+	  results. Each running CS procedure is allocated one buffer and the
+	  number of concurrent CS procedures is limited by this value.
+
 endif # BT_CONN
 
 rsource "Kconfig.iso"