1 files changed, 80 insertions, 1 deletions

diff --git a/include/osmocom/bsc/handover.h b/include/osmocom/bsc/handover.h
index bbb448c9d..0fbfaf671 100644
--- a/include/osmocom/bsc/handover.h
+++ b/include/osmocom/bsc/handover.h
@@ -1,12 +1,91 @@
 #pragma once
 
+#include <stdint.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/timer.h>
+
 struct gsm_lchan;
 struct gsm_bts;
 struct gsm_subscriber_connection;
 
-int bsc_handover_start(struct gsm_lchan *old_lchan, struct gsm_bts *new_bts,
+#define LOGPHOLCHANTOLCHAN(old_lchan, new_lchan, level, fmt, args...) \
+	LOGP(DHODEC, level, "(BTS %u trx %u arfcn %u ts %u lchan %u %s)->(BTS %u trx %u arfcn %u ts %u lchan %u %s) (subscr %s) " fmt, \
+	     old_lchan->ts->trx->bts->nr, \
+	     old_lchan->ts->trx->nr, \
+	     old_lchan->ts->trx->arfcn, \
+	     old_lchan->ts->nr, \
+	     old_lchan->nr, \
+	     gsm_pchan_name(old_lchan->ts->pchan), \
+	     new_lchan->ts->trx->bts->nr, \
+	     new_lchan->ts->trx->nr, \
+	     new_lchan->ts->trx->arfcn, \
+	     new_lchan->ts->nr, \
+	     new_lchan->nr, \
+	     gsm_pchan_name(new_lchan->ts->pchan), \
+	     bsc_subscr_name(old_lchan->conn? old_lchan->conn->bsub : NULL), \
+	     ## args)
+
+#define LOGPHO(struct_bsc_handover, level, fmt, args ...) \
+	LOGPHOLCHANTOLCHAN(struct_bsc_handover->old_lchan, struct_bsc_handover->new_lchan, level, fmt, ## args)
+
+enum hodec_id {
+	HODEC_NONE,
+	HODEC1 = 1,
+	HODEC2 = 2,
+};
+
+struct bsc_handover {
+	struct llist_head list;
+
+	enum hodec_id from_hodec_id;
+
+	struct gsm_lchan *old_lchan;
+	struct gsm_lchan *new_lchan;
+
+	struct osmo_timer_list T3103;
+
+	uint8_t ho_ref;
+
+	bool inter_cell;
+	bool async;
+};
+
+int bsc_handover_start(enum hodec_id from_hodec_id, struct gsm_lchan *old_lchan, struct gsm_bts *new_bts,
 		       enum gsm_chan_t new_lchan_type);
 void bsc_clear_handover(struct gsm_subscriber_connection *conn, int free_lchan);
 struct gsm_lchan *bsc_handover_pending(struct gsm_lchan *new_lchan);
 
 int bsc_ho_count(struct gsm_bts *bts, bool inter_cell);
+
+/* Handover decision algorithms' actions to take on incoming handover-relevant events.
+ *
+ * All events that are interesting for handover decision are actually communicated by S_LCHAN_* signals,
+ * so theoretically, each handover algorithm could evaluate those.  However, handover_logic.c cleans up
+ * handover operation state upon receiving some of these signals. To allow a handover decision algorithm
+ * to take advantage of e.g. the struct bsc_handover before it is discarded, the handover decision event
+ * handler needs to be invoked before handover_logic.c discards the state. For example, if the handover
+ * decision wants to place a penalty timer upon a handover failure, it still needs to know which target
+ * cell the handover failed for; handover_logic.c erases that knowledge on handover failure, since it
+ * needs to clean up the lchan's handover state.
+ *
+ * The most explicit and safest way to ensure the correct order of event handling is to invoke the
+ * handover decision algorithm's actions from handover_logic.c itself, before cleaning up. This struct
+ * provides the callback functions for this purpose.
+ *
+ * For consistency, also handle signals in this way that aren't actually in danger of interference from
+ * handover_logic.c (which also saves repeated lookup of handover state for lchans). Thus, handover
+ * decision algorithms should not register any signal handler at all.
+ */
+struct handover_decision_callbacks {
+	struct llist_head entry;
+
+	int hodec_id;
+
+	void (*on_measurement_report)(struct gsm_meas_rep *mr);
+	void (*on_ho_chan_activ_nack)(struct bsc_handover *ho);
+	void (*on_ho_failure)(struct bsc_handover *ho);
+};
+
+void handover_decision_callbacks_register(struct handover_decision_callbacks *hdc);
+struct handover_decision_callbacks *handover_decision_callbacks_get(int hodec_id);