ta_control: make 'struct bts_ul_meas' parameters const

The only reason why it was not 'const' is that in lchan_new_ul_meas()
we may need to overwrite 'ulm->is_sub'.  This can still be done after
memcpy()ing a new set of samples to the destination buffer.

Change-Id: I0cabf75f8e0bf793c01225a4a8433e994c93f562
Related: OS#5024

3 files changed, 19 insertions, 10 deletions

diff --git a/include/osmo-bts/measurement.h b/include/osmo-bts/measurement.h
index 8e91c334..45f275f1 100644
--- a/include/osmo-bts/measurement.h
+++ b/include/osmo-bts/measurement.h
@@ -4,11 +4,15 @@
 #define MEAS_MAX_TIMING_ADVANCE 63
 #define MEAS_MIN_TIMING_ADVANCE 0
 
-int lchan_new_ul_meas(struct gsm_lchan *lchan, struct bts_ul_meas *ulm, uint32_t fn);
+int lchan_new_ul_meas(struct gsm_lchan *lchan,
+		      const struct bts_ul_meas *ulm,
+		      uint32_t fn);
 
 int lchan_meas_check_compute(struct gsm_lchan *lchan, uint32_t fn);
 
-int lchan_meas_process_measurement(struct gsm_lchan *lchan, struct bts_ul_meas *ulm, uint32_t fn);
+int lchan_meas_process_measurement(struct gsm_lchan *lchan,
+				   const struct bts_ul_meas *ulm,
+				   uint32_t fn);
 
 void lchan_meas_reset(struct gsm_lchan *lchan);
 
diff --git a/src/common/measurement.c b/src/common/measurement.c
index 95d60f67..03afaa3e 100644
--- a/src/common/measurement.c
+++ b/src/common/measurement.c
@@ -318,9 +318,12 @@ static uint8_t modulus_by_lchan(struct gsm_lchan *lchan)
 
 /* receive a L1 uplink measurement from L1 (this function is only used
  * internally, it is public to call it from unit-tests)  */
-int lchan_new_ul_meas(struct gsm_lchan *lchan, struct bts_ul_meas *ulm, uint32_t fn)
+int lchan_new_ul_meas(struct gsm_lchan *lchan,
+		      const struct bts_ul_meas *ulm,
+		      uint32_t fn)
 {
 	uint32_t fn_mod = fn % modulus_by_lchan(lchan);
+	struct bts_ul_meas *dest;
 
 	if (lchan->state != LCHAN_S_ACTIVE) {
 		LOGPFN(DMEAS, LOGL_NOTICE, fn,
@@ -336,19 +339,19 @@ int lchan_new_ul_meas(struct gsm_lchan *lchan, struct bts_ul_meas *ulm, uint32_t
 		return -ENOSPC;
 	}
 
+	dest = &lchan->meas.uplink[lchan->meas.num_ul_meas++];
+	memcpy(dest, ulm, sizeof(*ulm));
+
 	/* We expect the lower layers to mark AMR SID_UPDATE frames already as such.
 	 * In this function, we only deal with the common logic as per the TS 45.008 tables */
 	if (!ulm->is_sub)
-		ulm->is_sub = ts45008_83_is_sub(lchan, fn);
+		dest->is_sub = ts45008_83_is_sub(lchan, fn);
 
 	DEBUGPFN(DMEAS, fn, "%s adding measurement (ber10k=%u, ta_offs=%d, ci=%0.2f, is_sub=%u, rssi=-%u), num_ul_meas=%d, fn_mod=%u\n",
 		 gsm_lchan_name(lchan), ulm->ber10k, ulm->ta_offs_256bits,
-		 ulm->c_i, ulm->is_sub, ulm->inv_rssi, lchan->meas.num_ul_meas,
+		 ulm->c_i, dest->is_sub, ulm->inv_rssi, lchan->meas.num_ul_meas,
 		 fn_mod);
 
-	memcpy(&lchan->meas.uplink[lchan->meas.num_ul_meas++], ulm,
-		sizeof(*ulm));
-
 	lchan->meas.last_fn = fn;
 
 	return 0;
@@ -757,7 +760,9 @@ int lchan_meas_check_compute(struct gsm_lchan *lchan, uint32_t fn)
  * l1sap.c every time a measurement indication is received. It collects the
  * measurement samples and automatically detects the end of the measurement
  * interval. */
-int lchan_meas_process_measurement(struct gsm_lchan *lchan, struct bts_ul_meas *ulm, uint32_t fn)
+int lchan_meas_process_measurement(struct gsm_lchan *lchan,
+				   const struct bts_ul_meas *ulm,
+				   uint32_t fn)
 {
 	lchan_new_ul_meas(lchan, ulm, fn);
 	return lchan_meas_check_compute(lchan, fn);
diff --git a/tests/meas/meas_test.c b/tests/meas/meas_test.c
index 174abbe6..d1293365 100644
--- a/tests/meas/meas_test.c
+++ b/tests/meas/meas_test.c
@@ -89,7 +89,7 @@ static void test_meas_compute(const struct meas_testcase *mtc)
 
 	/* feed uplink measurements into the code */
 	for (i = 0; i < mtc->ulm_count; i++) {
-		lchan_new_ul_meas(lchan, (struct bts_ul_meas *) &mtc->ulm[i], fn);
+		lchan_new_ul_meas(lchan, &mtc->ulm[i], fn);
 		fn += 1;
 	}