add gsm48_number_of_paging_subchannels() function

(from openbsc's rsl_number_of_paging_subchannels)

diff --git a/include/osmocom/gsm/gsm48.h b/include/osmocom/gsm/gsm48.h
index 1e9403b..16a625a 100644 (file)
--- a/include/osmocom/gsm/gsm48.h
+++ b/include/osmocom/gsm/gsm48.h
@@ -33,4 +33,6 @@ int gsm48_mi_to_string(char *string, const int str_len,
 void gsm48_parse_ra(struct gprs_ra_id *raid, const uint8_t *buf);
 int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid);
 
+int gsm48_number_of_paging_subchannels(struct gsm48_control_channel_descr *chan_desc);
+
 #endif

diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index d034589..4645af4 100644 (file)
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -33,6 +33,7 @@
 #include <osmocom/gsm/gsm48.h>
 
 #include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gsm/protocol/gsm_08_58.h>
 
 const struct tlv_definition gsm48_att_tlvdef = {
        .def = {
@@ -413,3 +414,15 @@ int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid)
 
        return 6;
 }
+
+/* From Table 10.5.33 of GSM 04.08 */
+int gsm48_number_of_paging_subchannels(struct gsm48_control_channel_descr *chan_desc)
+{
+       if (chan_desc->ccch_conf == RSL_BCCH_CCCH_CONF_1_C) {
+               return OSMO_MAX(1, (3 - chan_desc->bs_ag_blks_res))
+                       * (chan_desc->bs_pa_mfrms + 2);
+       } else {
+               return (9 - chan_desc->bs_ag_blks_res)
+                       * (chan_desc->bs_pa_mfrms + 2);
+       }
+}