paging: add unit-test to check different bs_ag_blks_res settings

The parameter bs_ag_blks_res, which is loaded into the BTS via the SI3
setting, defines how many of the CCCH blocks shall be used for AGCH. The
remaining CCCH blocks will then be available as PCH for paging.
Unfortunately there is no unit-test yet that verifies that all of the 8
different settings for bs_ag_blks_res.

- Separate the the decision logic that checks if a given fn is part of
  an AGCH into a function to have it available in the unit-test.
- Add a test that checks all possible bs_ag_blks_res settings.

Change-Id: Ib9652f4013a4da3766852f8f03ce9ec5590f6989
Related: OS#1575

2 files changed, 76 insertions, 0 deletions

diff --git a/tests/paging/paging_test.c b/tests/paging/paging_test.c
index 0accd0fb..1fc7d928 100644
--- a/tests/paging/paging_test.c
+++ b/tests/paging/paging_test.c
@@ -25,6 +25,7 @@
 #include <osmo-bts/logging.h>
 #include <osmo-bts/paging.h>
 #include <osmo-bts/gsm_data.h>
+#include <osmo-bts/l1sap.h>
 
 #include <unistd.h>
 
@@ -110,6 +111,59 @@ static void test_paging_sleep(void)
 	ASSERT_TRUE(paging_queue_length(bts->paging_state) == 0);
 }
 
+/* Set up a dummy trx with a valid setting for bs_ag_blks_res in SI3 */
+static struct gsm_bts_trx *test_is_ccch_for_agch_setup(uint8_t bs_ag_blks_res)
+{
+	static struct gsm_bts_trx trx;
+	static struct gsm_bts bts;
+	struct gsm48_system_information_type_3 si3;
+	si3.control_channel_desc.bs_ag_blks_res = bs_ag_blks_res;
+	trx.bts = &bts;
+	bts.si_valid |= 0x8;
+	memcpy(&bts.si_buf[SYSINFO_TYPE_3][0], &si3, sizeof(si3));
+	return &trx;
+}
+
+/* Walk through all possible settings for bs_ag_blks_res for two
+ * multiframe 51. The patterns shown in 3GPP TS 05.02 Clause 7
+ * Table 5 of 9 must occur. */
+static void test_is_ccch_for_agch(void)
+{
+	int is_ag_res;
+	int fn;
+	uint8_t bs_ag_blks_res;
+	struct gsm_bts_trx *trx;
+
+	printf("Fn:   AGCH: (bs_ag_blks_res=[0:7]\n");
+	for (fn = 0; fn < 102; fn++) {
+
+		/* Note: the formula that computes the CCCH block number for a
+		 * given frame number is optimized to work on block boarders,
+		 * for frame numbers that do not fall at the beginning of the
+		 * related block this formula would produce wrong results, so
+		 * we only check with frame numbers that mark the beginning
+		 * of a new block. See also L1SAP_FN2CCCHBLOCK() in l1sap.h */
+
+		if (fn % 10 != 2 && fn % 10 != 6)
+			continue;
+
+		printf("%03u: ", fn);
+
+		if (fn % 50 == 2) {
+			printf(" . . . . . . . . (BCCH)\n");
+			continue;
+		}
+
+		/* Try allo possible settings for bs_ag_blks_res */
+		for (bs_ag_blks_res = 0; bs_ag_blks_res <= 7; bs_ag_blks_res++) {
+			trx = test_is_ccch_for_agch_setup(bs_ag_blks_res);
+			is_ag_res = is_ccch_for_agch(trx, fn);
+			printf(" %u", is_ag_res);
+		}
+		printf("\n");
+	}
+}
+
 int main(int argc, char **argv)
 {
 	tall_bts_ctx = talloc_named_const(NULL, 1, "OsmoBTS context");
@@ -125,6 +179,7 @@ int main(int argc, char **argv)
 
 	test_paging_smoke();
 	test_paging_sleep();
+	test_is_ccch_for_agch();
 	printf("Success\n");
 
 	return 0;
diff --git a/tests/paging/paging_test.ok b/tests/paging/paging_test.ok
index 57565e24..50006ec9 100644
--- a/tests/paging/paging_test.ok
+++ b/tests/paging/paging_test.ok
@@ -1,3 +1,24 @@
 Testing that paging messages expire.
 Testing that paging messages expire with sleep.
+Fn:   AGCH: (bs_ag_blks_res=[0:7]
+002:  . . . . . . . . (BCCH)
+006:  0 1 1 1 1 1 1 1
+012:  0 0 1 1 1 1 1 1
+016:  0 0 0 1 1 1 1 1
+022:  0 0 0 0 1 1 1 1
+026:  0 0 0 0 0 1 1 1
+032:  0 0 0 0 0 0 1 1
+036:  0 0 0 0 0 0 0 1
+042:  0 0 0 0 0 0 0 0
+046:  0 0 0 0 0 0 0 0
+052:  . . . . . . . . (BCCH)
+056:  0 1 1 1 1 1 1 1
+062:  0 0 1 1 1 1 1 1
+066:  0 0 0 1 1 1 1 1
+072:  0 0 0 0 1 1 1 1
+076:  0 0 0 0 0 1 1 1
+082:  0 0 0 0 0 0 1 1
+086:  0 0 0 0 0 0 0 1
+092:  0 0 0 0 0 0 0 0
+096:  0 0 0 0 0 0 0 0
 Success