From 94df39e905b9de424ecb40e9c54ddae0e7b6d4e3 Mon Sep 17 00:00:00 2001
From: Harald Welte <laforge@gnumonks.org>
Date: Sun, 26 Jun 2011 14:33:57 +0200
Subject: add some utility functions for paging related calculation (TS 05.02)

---
 include/osmocom/gsm/Makefile.am |  2 +-
 include/osmocom/gsm/gsm0502.h   | 35 +++++++++++++++++++++++++++++++++++
 src/gsm/gsm48.c                 | 14 +++++++-------
 3 files changed, 43 insertions(+), 8 deletions(-)
 create mode 100644 include/osmocom/gsm/gsm0502.h

diff --git a/include/osmocom/gsm/Makefile.am b/include/osmocom/gsm/Makefile.am
index aa7b1a9a..ce3ac9cb 100644
--- a/include/osmocom/gsm/Makefile.am
+++ b/include/osmocom/gsm/Makefile.am
@@ -1,6 +1,6 @@
 osmogsm_HEADERS = a5.h comp128.h gsm0808.h gsm48_ie.h mncc.h rxlev_stat.h \
 		  gsm0480.h gsm48.h gsm_utils.h rsl.h tlv.h abis_nm.h \
-		  sysinfo.h prim.h
+		  sysinfo.h prim.h gsm0502.h
 
 SUBDIRS = protocol
 
diff --git a/include/osmocom/gsm/gsm0502.h b/include/osmocom/gsm/gsm0502.h
new file mode 100644
index 00000000..de92c636
--- /dev/null
+++ b/include/osmocom/gsm/gsm0502.h
@@ -0,0 +1,35 @@
+#ifndef OSMOCOM_GSM_0502_H
+#define OSMOCOM_GSM_0502_H
+
+#include <stdint.h>
+
+#include <osmocom/gsm/protocol/gsm_04_08.h>
+#include <osmocom/gsm/protocol/gsm_08_58.h>
+
+/* Table 5 Clause 7 TS 05.02 */
+static inline unsigned int
+gsm0502_get_n_pag_blocks(struct gsm48_control_channel_descr *chan_desc)
+{
+	if (chan_desc->ccch_conf == RSL_BCCH_CCCH_CONF_1_C)
+		return 3 - chan_desc->bs_ag_blks_res;
+	else
+		return 9 - chan_desc->bs_ag_blks_res;
+}
+
+/* Chapter 6.5.2 of TS 05.02 */
+static inline unsigned int
+gsm0502_get_ccch_group(uint64_t imsi, unsigned int bs_cc_chans,
+			unsigned int n_pag_blocks)
+{
+	return (imsi % 1000) % (bs_cc_chans * n_pag_blocks) / n_pag_blocks;
+}
+
+/* Chapter 6.5.2 of TS 05.02 */
+static inline unsigned int
+gsm0502_get_paging_group(uint64_t imsi, unsigned int bs_cc_chans,
+			 int n_pag_blocks)
+{
+	return (imsi % 1000) % (bs_cc_chans * n_pag_blocks) % n_pag_blocks;
+}
+
+#endif
diff --git a/src/gsm/gsm48.c b/src/gsm/gsm48.c
index 4645af4d..44baec60 100644
--- a/src/gsm/gsm48.c
+++ b/src/gsm/gsm48.c
@@ -31,6 +31,7 @@
 #include <osmocom/core/utils.h>
 #include <osmocom/gsm/tlv.h>
 #include <osmocom/gsm/gsm48.h>
+#include <osmocom/gsm/gsm0502.h>
 
 #include <osmocom/gsm/protocol/gsm_04_08.h>
 #include <osmocom/gsm/protocol/gsm_08_58.h>
@@ -418,11 +419,10 @@ int gsm48_construct_ra(uint8_t *buf, const struct gprs_ra_id *raid)
 /* 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);
-	}
+	unsigned int n_pag_blocks = gsm0502_get_n_pag_blocks(chan_desc);
+
+	if (chan_desc->ccch_conf == RSL_BCCH_CCCH_CONF_1_C)
+		return OSMO_MAX(1, n_pag_blocks) * (chan_desc->bs_pa_mfrms + 2);
+	else
+		return n_pag_blocks * (chan_desc->bs_pa_mfrms + 2);
 }
-- 
cgit v1.2.3