refactor lchan counting

Add chan_counts_for_trx() and chan_counts_for_bts(). Drop
bts_count_free_ts() and trx_count_free_ts().

Rationale:

The bts_count_free_ts() and trx_count_free_ts() always returned the
number of free lchans, not timeslots. Hence, passing the pchan type as
argument never really matched the semantics.

Especially, when looking for free SDCCH, there is no clear match on a
gsm_phys_chan_config enum value: SDCCH8_SACCH8C, CCCH_SDCCH4,
CCCH_SDCCH4_CBCH, SDCCH8_SACCH8C_CBCH? -- GSM_LCHAN_SDCCH is clear.

==> Rather count free lchans by enum gsm_chan_t.

Counting lchans of distinct types required separate iterations for each
lchan type.

==> Rather compose an array of counts for all types, in one go.

I need to count the amount of free SDCCH lchans in an upcoming patch to
implement the performance indicator allAvailableAllocatedSDCCH (cumulate
time for which no SDCCH are available).

To implement allAvailableAllocated{SDCCH,TCH}, I need a count of both
the used as well as the total lchans for a type: it does not make sense
to flag "all available allocated" if none are ever available.

To properly count dynamic ts, I need the maximum total that can be
possible at any time. And to count currently free lchans, I need the
current total. This may seem counter intuitive, but consider, e.g.:

- Obviously, if a cell has only static TCH/F timeslots, it does not make
  sense to flag that all available TCH/H are occupied, because no TCH/H
  are available ever. Just stating this as contrast to dyn TS.

- If a cell has OSMO_DYN timeslots, I *do* want to flag that all TCH/H
  are occupied when all dyn timeslots are fully occupied.

- If those OSMO_DYN however are all used as TCH/F, the current total of
  TCH/H becomes zero, and it seems like TCH/H should not be considered.

- To count the nr of currently free lchans, I need the currently
  possible total of lchans and the nr of occupied lchans.

So return both a maximum total and a current total of lchans. In above
example, the maximum total shows that there would be TCH/H possible.

BTW, it would be nice to keep a chan_counts array on trx, bts and bsc
level and update as channels are allocated and released, instead of
counting them all over periodically. But it's less error prone this way.

Related: SYS#4878
Change-Id: I2fb48c549186db812b1e9d6b735a92e80f27b8d3

4 files changed, 77 insertions, 3 deletions

diff --git a/include/osmocom/bsc/Makefile.am b/include/osmocom/bsc/Makefile.am
index 3bccf44fd..3ddad45db 100644
--- a/include/osmocom/bsc/Makefile.am
+++ b/include/osmocom/bsc/Makefile.am
@@ -16,6 +16,7 @@ noinst_HEADERS = \
 	bts_trx.h \
 	bts_ipaccess_nanobts_omlattr.h \
 	chan_alloc.h \
+	chan_counts.h \
 	codec_pref.h \
 	ctrl.h \
 	debug.h \
diff --git a/include/osmocom/bsc/bts.h b/include/osmocom/bsc/bts.h
index 7e73acd9d..c887ca882 100644
--- a/include/osmocom/bsc/bts.h
+++ b/include/osmocom/bsc/bts.h
@@ -726,8 +726,6 @@ void gsm_bts_set_radio_link_timeout(struct gsm_bts *bts, int value);
 
 void gsm_bts_all_ts_dispatch(struct gsm_bts *bts, uint32_t ts_ev, void *data);
 
-int bts_count_free_ts(struct gsm_bts *bts, enum gsm_phys_chan_config pchan);
-
 int gsm_bts_set_system_infos(struct gsm_bts *bts);
 
 int gsm_bts_set_c0_power_red(struct gsm_bts *bts, const uint8_t red);
diff --git a/include/osmocom/bsc/bts_trx.h b/include/osmocom/bsc/bts_trx.h
index 4d705d0d9..c8df9d9c4 100644
--- a/include/osmocom/bsc/bts_trx.h
+++ b/include/osmocom/bsc/bts_trx.h
@@ -95,7 +95,6 @@ void gsm_trx_lock_rf(struct gsm_bts_trx *trx, bool locked, const char *reason);
 bool trx_is_usable(const struct gsm_bts_trx *trx);
 
 void gsm_trx_all_ts_dispatch(struct gsm_bts_trx *trx, uint32_t ts_ev, void *data);
-int trx_count_free_ts(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan);
 bool trx_has_valid_pchan_config(const struct gsm_bts_trx *trx);
 
 int gsm_bts_trx_set_system_infos(struct gsm_bts_trx *trx);
diff --git a/include/osmocom/bsc/chan_counts.h b/include/osmocom/bsc/chan_counts.h
new file mode 100644
index 000000000..9f73bc418
--- /dev/null
+++ b/include/osmocom/bsc/chan_counts.h
@@ -0,0 +1,76 @@
+/* API to count total, allocated and free channels of all types */
+#pragma once
+
+struct gsm_bts;
+struct gsm_bts_trx;
+
+/* First array index to typedef chan_counts_arr. */
+enum chan_counts_dim1 {
+	CHAN_COUNTS1_ALL = 0,
+	CHAN_COUNTS1_STATIC = 1,
+	CHAN_COUNTS1_DYNAMIC = 2,
+	_CHAN_COUNTS1_NUM
+};
+
+/* Second array index to typedef chan_counts_arr. */
+enum chan_counts_dim2 {
+	/* The maximum possible nr of lchans of this type. Counts all dynamic timeslots as if they are fully available
+	 * for this type, regardless of the current pchan mode. (For CHAN_COUNTS1_STATIC, of course no dyn TS are counted
+	 * at all.) */
+	CHAN_COUNTS2_MAX_TOTAL = 0,
+	/* Like MAX_TOTAL, but as soon as dynamic timeslots are switched to a specific pchan kind, current_total shrinks
+	 * to count only currently present lchans (used and unused). */
+	CHAN_COUNTS2_CURRENT_TOTAL = 1,
+	/* Currently used lchans of this type. To get currently free lchans, calculate CURRENT_TOTAL - ALLOCATED. */
+	CHAN_COUNTS2_ALLOCATED = 2,
+	/* Currently assignable lchans of this type, same as CURRENT_TOTAL - ALLOCATED. */
+	CHAN_COUNTS2_FREE = 3,
+	_CHAN_COUNTS2_NUM
+};
+
+struct chan_counts {
+	unsigned int val[_CHAN_COUNTS1_NUM][_CHAN_COUNTS2_NUM][_GSM_LCHAN_MAX];
+};
+
+void chan_counts_for_bts(struct chan_counts *bts_counts, const struct gsm_bts *bts);
+void chan_counts_for_trx(struct chan_counts *trx_counts, const struct gsm_bts_trx *trx);
+
+static inline void chan_counts_zero(struct chan_counts *counts)
+{
+	*counts = (struct chan_counts){0};
+}
+
+static inline void chan_counts_dim3_add(struct chan_counts *dst,
+					enum chan_counts_dim1 dst_dim1, enum chan_counts_dim2 dst_dim2,
+					const struct chan_counts *add,
+					enum chan_counts_dim1 add_dim1, enum chan_counts_dim2 add_dim2)
+{
+	int i;
+	for (i = 0; i < _GSM_LCHAN_MAX; i++)
+		dst->val[dst_dim1][dst_dim2][i] += add->val[add_dim1][add_dim2][i];
+}
+
+static inline void chan_counts_dim3_sub(struct chan_counts *dst,
+					enum chan_counts_dim1 dst_dim1, enum chan_counts_dim2 dst_dim2,
+					const struct chan_counts *sub,
+					enum chan_counts_dim1 sub_dim1, enum chan_counts_dim2 sub_dim2)
+{
+	int i;
+	for (i = 0; i < _GSM_LCHAN_MAX; i++)
+		dst->val[dst_dim1][dst_dim2][i] -= sub->val[sub_dim1][sub_dim2][i];
+}
+
+static inline void chan_counts_dim2_add(struct chan_counts *dst, enum chan_counts_dim1 dst_dim1,
+					const struct chan_counts *add, enum chan_counts_dim1 add_dim1)
+{
+	int i;
+	for (i = 0; i < _CHAN_COUNTS2_NUM; i++)
+		chan_counts_dim3_add(dst, dst_dim1, i, add, add_dim1, i);
+}
+
+static inline void chan_counts_add(struct chan_counts *dst, const struct chan_counts *add)
+{
+	int i;
+	for (i = 0; i < _CHAN_COUNTS1_NUM; i++)
+		chan_counts_dim2_add(dst, i, add, i);
+}