host/trxcon: split sched_lchan_handlers.c

It would be better to have xCCH, SCH and RACH burst handlers
in separate files, because as much code we add to a single
file, as harder it becomes to read and understand one.

Change-Id: I456a60e68b32b792e63dd03ae97159dc101fd4bf

1 files changed, 137 insertions, 0 deletions

diff --git a/src/host/trxcon/sched_lchan_sch.c b/src/host/trxcon/sched_lchan_sch.c
new file mode 100644
index 00000000..9e854bbf
--- /dev/null
+++ b/src/host/trxcon/sched_lchan_sch.c
@@ -0,0 +1,137 @@
+/*
+ * OsmocomBB <-> SDR connection bridge
+ * TDMA scheduler: handlers for DL / UL bursts on logical channels
+ *
+ * (C) 2017 by Vadim Yanitskiy <axilirator@gmail.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <errno.h>
+#include <string.h>
+#include <talloc.h>
+#include <stdint.h>
+
+#include <arpa/inet.h>
+
+#include <osmocom/core/linuxlist.h>
+#include <osmocom/core/logging.h>
+#include <osmocom/core/bits.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/core/fsm.h>
+
+#include <osmocom/gsm/gsm_utils.h>
+#include <osmocom/coding/gsm0503_coding.h>
+
+#include "l1ctl_proto.h"
+#include "scheduler.h"
+#include "sched_trx.h"
+#include "logging.h"
+#include "trx_if.h"
+#include "trxcon.h"
+#include "l1ctl.h"
+
+static void decode_sb(struct gsm_time *time, uint8_t *bsic, uint8_t *sb_info)
+{
+	uint8_t t3p;
+	uint32_t sb;
+
+	sb = (sb_info[3] << 24)
+	   | (sb_info[2] << 16)
+	   | (sb_info[1] << 8)
+	   | sb_info[0];
+
+	*bsic = (sb >> 2) & 0x3f;
+
+	/* TS 05.02 Chapter 3.3.2.2.1 SCH Frame Numbers */
+	time->t1 = ((sb >> 23) & 0x01)
+		 | ((sb >> 7) & 0x1fe)
+		 | ((sb << 9) & 0x600);
+
+	time->t2 = (sb >> 18) & 0x1f;
+
+	t3p = ((sb >> 24) & 0x01) | ((sb >> 15) & 0x06);
+	time->t3 = t3p * 10 + 1;
+
+	/* TS 05.02 Chapter 4.3.3 TDMA frame number */
+	time->fn = gsm_gsmtime2fn(time);
+}
+
+int rx_sch_fn(struct trx_instance *trx, struct trx_ts *ts,
+	uint32_t fn, enum trx_lchan_type chan, uint8_t bid,
+	sbit_t *bits, uint16_t nbits, int8_t rssi, float toa)
+{
+	sbit_t payload[2 * 39];
+	struct gsm_time time;
+	uint8_t sb_info[4];
+	uint8_t bsic;
+	int rc;
+
+	/* Obtain payload from burst */
+	memcpy(payload, bits + 3, 39);
+	memcpy(payload + 39, bits + 3 + 39 + 64, 39);
+
+	/* Attempt to decode */
+	rc = gsm0503_sch_decode(sb_info, payload);
+	if (rc) {
+		LOGP(DSCH, LOGL_DEBUG, "Received bad SCH burst at fn=%u\n", fn);
+		return rc;
+	}
+
+	/* Decode BSIC and TDMA frame number */
+	decode_sb(&time, &bsic, sb_info);
+
+	LOGP(DSCH, LOGL_DEBUG, "Received SCH: bsic=%u, fn=%u, sched_fn=%u\n",
+		bsic, time.fn, trx->sched.fn_counter_proc);
+
+	/* Check if decoded frame number matches */
+	if (time.fn != fn) {
+		LOGP(DSCH, LOGL_ERROR, "Decoded fn=%u does not match "
+			"fn=%u provided by scheduler\n", time.fn, fn);
+		return -EINVAL;
+	}
+
+	/* We don't need to send L1CTL_FBSB_CONF */
+	if (trx->l1l->fbsb_conf_sent)
+		return 0;
+
+	/* Send L1CTL_FBSB_CONF to higher layers */
+	struct l1ctl_info_dl *data;
+	data = talloc_zero_size(ts, sizeof(struct l1ctl_info_dl));
+	if (data == NULL)
+		return -ENOMEM;
+
+	/* Fill in some downlink info */
+	data->chan_nr = trx_lchan_desc[chan].chan_nr | ts->index;
+	data->link_id = trx_lchan_desc[chan].link_id;
+	data->band_arfcn = htons(trx->band_arfcn);
+	data->frame_nr = htonl(fn);
+	data->rx_level = -rssi;
+
+	/* FIXME: set proper values */
+	data->num_biterr = 0;
+	data->fire_crc = 0;
+	data->snr = 0;
+
+	l1ctl_tx_fbsb_conf(trx->l1l, 0, data, bsic);
+
+	/* Update BSIC value of trx_instance */
+	trx->bsic = bsic;
+
+	return 0;
+}