1 files changed, 304 insertions, 0 deletions
diff --git a/src/host/trxcon/sched_lchan_xcch.c b/src/host/trxcon/sched_lchan_xcch.c
new file mode 100644
index 00000000..12bb6ee5
--- /dev/null
+++ b/src/host/trxcon/sched_lchan_xcch.c
@@ -0,0 +1,304 @@
+/*
+ * 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"
+
+/* GSM 05.02 Chapter 5.2.3 Normal Burst (NB) */
+static const uint8_t nb_training_bits[8][26] = {
+	{
+		0, 0, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0,
+		0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 1,
+	},
+	{
+		0, 0, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 1,
+		1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 1, 1, 1,
+	},
+	{
+		0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1,
+		0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0,
+	},
+	{
+		0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0,
+		1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0,
+	},
+	{
+		0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0,
+		1, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1,
+	},
+	{
+		0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 1, 1, 0,
+		0, 0, 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0,
+	},
+	{
+		1, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1,
+		0, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1, 1,
+	},
+	{
+		1, 1, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 0,
+		0, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0,
+	},
+};
+
+int rx_data_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)
+{
+	int n_errors, n_bits_total, rc;
+	struct trx_lchan_state *lchan;
+	uint8_t *rssi_num, *toa_num;
+	float *rssi_sum, *toa_sum;
+	sbit_t *buffer, *offset;
+	uint8_t l2[23], *mask;
+	uint32_t *first_fn;
+
+	LOGP(DSCH, LOGL_DEBUG, "Data received on %s: fn=%u ts=%u bid=%u\n",
+		trx_lchan_desc[chan].name, fn, ts->index, bid);
+
+	/* Find required channel state */
+	lchan = sched_trx_find_lchan(ts, chan);
+	if (lchan == NULL)
+		return -EINVAL;
+
+	/* Set up pointers */
+	first_fn = &lchan->rx_first_fn;
+	mask = &lchan->rx_burst_mask;
+	buffer = lchan->rx_bursts;
+
+	rssi_sum = &lchan->rssi_sum;
+	rssi_num = &lchan->rssi_num;
+	toa_sum = &lchan->toa_sum;
+	toa_num = &lchan->toa_num;
+
+	/* Clear buffer & store frame number of first burst */
+	if (bid == 0) {
+		memset(buffer, 0, 464);
+
+		*first_fn = fn;
+		*mask = 0x0;
+
+		*rssi_sum = 0;
+		*rssi_num = 0;
+		*toa_sum = 0;
+		*toa_num = 0;
+	}
+
+	/* Update mask and RSSI */
+	*mask |= (1 << bid);
+	*rssi_sum += rssi;
+	(*rssi_num)++;
+	*toa_sum += toa;
+	(*toa_num)++;
+
+	/* Copy burst to buffer of 4 bursts */
+	offset = buffer + bid * 116;
+	memcpy(offset, bits + 3, 58);
+	memcpy(offset + 58, bits + 87, 58);
+
+	/* Wait until complete set of bursts */
+	if (bid != 3)
+		return 0;
+
+	/* Check for complete set of bursts */
+	if ((*mask & 0xf) != 0xf) {
+		LOGP(DSCH, LOGL_DEBUG, "Received incomplete data frame at "
+			"fn=%u (%u/%u) for %s\n", *first_fn,
+			(*first_fn) % ts->mf_layout->period,
+			ts->mf_layout->period,
+			trx_lchan_desc[chan].name);
+
+		/* We require first burst to have correct FN */
+		if (!(*mask & 0x1)) {
+			*mask = 0x0;
+			return 0;
+		}
+
+		/* FIXME: return from here? */
+	}
+
+	/* Attempt to decode */
+	rc = gsm0503_xcch_decode(l2, buffer, &n_errors, &n_bits_total);
+	if (rc) {
+		LOGP(DSCH, LOGL_DEBUG, "Received bad data frame at fn=%u "
+			"(%u/%u) for %s\n", *first_fn,
+			(*first_fn) % ts->mf_layout->period,
+			ts->mf_layout->period,
+			trx_lchan_desc[chan].name);
+		return rc;
+	}
+
+	/* Compose a message to the higher layers */
+	struct l1ctl_info_dl *data;
+	data = talloc_zero_size(ts, sizeof(struct l1ctl_info_dl) + 23);
+	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(*first_fn);
+	data->rx_level = -(*rssi_sum / *rssi_num);
+
+	/* FIXME: set proper values */
+	data->num_biterr = n_errors;
+	data->fire_crc = 0;
+	data->snr = 0;
+
+	/* Fill in decoded payload */
+	memcpy(data->payload, l2, 23);
+
+	/* Put a packet to higher layers */
+	l1ctl_tx_data_ind(trx->l1l, data);
+	talloc_free(data);
+
+	/* TODO: AGC, TA loops */
+	return 0;
+}
+
+int tx_data_fn(struct trx_instance *trx, struct trx_ts *ts,
+	uint32_t fn, enum trx_lchan_type chan,
+	uint8_t bid, uint16_t *nbits)
+{
+	struct trx_lchan_state *lchan;
+	struct trx_ts_prim *prim;
+	struct l1ctl_info_ul *ul;
+	ubit_t burst[GSM_BURST_LEN];
+	ubit_t *buffer, *offset;
+	uint8_t *mask, *l2;
+	const uint8_t *tsc;
+	int rc;
+
+	/* Find required channel state */
+	lchan = sched_trx_find_lchan(ts, chan);
+	if (lchan == NULL)
+		return -EINVAL;
+
+	/* Set up pointers */
+	mask = &lchan->tx_burst_mask;
+	buffer = lchan->tx_bursts;
+
+	if (bid > 0) {
+		/* If we have encoded bursts */
+		if (*mask)
+			goto send_burst;
+		else
+			return 0;
+	}
+
+	/* Encode payload if not yet */
+
+	/* Get a message from TX queue */
+	prim = llist_entry(ts->tx_prims.next, struct trx_ts_prim, list);
+	ul = (struct l1ctl_info_ul *) prim->payload;
+	l2 = (uint8_t *) ul->payload;
+
+	/* Encode bursts */
+	rc = gsm0503_xcch_encode(buffer, l2);
+	if (rc) {
+		LOGP(DSCH, LOGL_ERROR, "Failed to encode L2 payload\n");
+
+		/* Remove primitive from queue and free memory */
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		return -EINVAL;
+	}
+
+send_burst:
+	/* Determine which burst should be sent */
+	offset = buffer + bid * 116;
+
+	/* Update mask */
+	*mask |= (1 << bid);
+
+	/* Choose proper TSC */
+	tsc = nb_training_bits[trx->tsc];
+
+	/* Compose a new burst */
+	memset(burst, 0, 3); /* TB */
+	memcpy(burst + 3, offset, 58); /* Payload 1/2 */
+	memcpy(burst + 61, tsc, 26); /* TSC */
+	memcpy(burst + 87, offset + 58, 58); /* Payload 2/2 */
+	memset(burst + 145, 0, 3); /* TB */
+
+	if (nbits)
+		*nbits = GSM_BURST_LEN;
+
+	LOGP(DSCH, LOGL_DEBUG, "Transmitting %s fn=%u ts=%u burst=%u\n",
+		trx_lchan_desc[chan].name, fn, ts->index, bid);
+
+	/* Send burst to transceiver */
+	rc = trx_if_tx_burst(trx, ts->index, fn, 10, burst);
+	if (rc) {
+		LOGP(DSCH, LOGL_ERROR, "Could not send burst to transceiver\n");
+
+		/* Remove primitive from queue and free memory */
+		prim = llist_entry(ts->tx_prims.next, struct trx_ts_prim, list);
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		/* Reset mask */
+		*mask = 0x00;
+
+		return rc;
+	}
+
+	/* If we have sent the last (4/4) burst */
+	if ((*mask & 0x0f) == 0x0f) {
+		/* Remove primitive from queue and free memory */
+		prim = llist_entry(ts->tx_prims.next, struct trx_ts_prim, list);
+		llist_del(&prim->list);
+		talloc_free(prim);
+
+		/* Reset mask */
+		*mask = 0x00;
+
+		/* Confirm data sending */
+		l1ctl_tx_data_conf(trx->l1l);
+	}
+
+	return 0;
+}