Set DTX in Cell Options

* rename field of struct gsm48_cell_options to better match the spec
* add comments with spec references
* add function for setting DTX in cell options struct
* add necessary enum type

Change-Id: I5a8924f57669c951b2e51b663d95f1d360062a54
Reviewed-on: https://gerrit.osmocom.org/39
Reviewed-by: Harald Welte <laforge@gnumonks.org>
Tested-by: Jenkins Builder

1 files changed, 45 insertions, 1 deletions

diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index ab626050..8a46f769 100644
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -25,7 +25,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
-
+#include <stdbool.h>
 #include <arpa/inet.h>
 
 #include <osmocom/core/utils.h>
@@ -358,6 +358,50 @@ int gsm48_decode_lai(struct gsm48_loc_area_id *lai, uint16_t *mcc,
 	return 0;
 }
 
+/*! \brief Set DTX mode in Cell Options IE (3GPP TS 44.018)
+ *  \param[in] op Cell Options structure in which DTX parameters will be set
+ *  \param[in] full Mode for full-rate channels
+ *  \param[in] half Mode for half-rate channels
+ *  \param[in] is_bcch Indicates if we should use 10.5.2.3.1 instead of
+ *             10.5.2.3a.2
+ *
+ * There is no space for separate DTX settings for Full and Half rate channels
+ * in BCCH - in this case full setting is used for both and half parameter is
+ * ignored.
+ */
+void gsm48_set_dtx(struct gsm48_cell_options *op, enum gsm48_dtx_mode full,
+		   enum gsm48_dtx_mode half, bool is_bcch)
+{
+	if (is_bcch) {
+		switch (full) {
+		case GSM48_DTX_MAY_BE_USED:
+			op->dtx = 0;
+			return;
+		case GSM48_DTX_SHALL_BE_USED:
+			op->dtx = 1;
+			return;
+		case GSM48_DTX_SHALL_NOT_BE_USED:
+			op->dtx = 2;
+			return;
+		}
+	} else {
+		switch (full) {
+		case GSM48_DTX_MAY_BE_USED:
+			op->dtx = (half == GSM48_DTX_SHALL_BE_USED) ? 3 : 0;
+			op->d =   (half == GSM48_DTX_SHALL_NOT_BE_USED) ? 0 : 1;
+			return;
+		case GSM48_DTX_SHALL_BE_USED:
+			op->dtx = (half == GSM48_DTX_MAY_BE_USED) ? 3 : 1;
+			op->d =   (half == GSM48_DTX_SHALL_BE_USED) ? 1 : 0;
+			return;
+		case GSM48_DTX_SHALL_NOT_BE_USED:
+			op->dtx = 2;
+			op->d =   (half == GSM48_DTX_SHALL_BE_USED) ? 1 : 0;
+			return;
+		}
+	}
+}
+
 int gsm48_generate_mid_from_tmsi(uint8_t *buf, uint32_t tmsi)
 {
 	uint32_t tmsi_be = htonl(tmsi);