diff --git a/openbsc/src/libabis/input/hsl.c b/openbsc/src/libabis/input/hsl.c
new file mode 100644
index 0000000..12e974b
--- /dev/null
+++ b/openbsc/src/libabis/input/hsl.c
@@ -0,0 +1,457 @@
+/* OpenBSC Abis input driver for HSL Femto */
+
+/* (C) 2011 by Harald Welte <laforge@gnumonks.org>
+ * (C) 2011 by On-Waves
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+/* HSL uses a much more primitive/simplified version of the IPA multiplex.
+ *
+ * They have taken out the nice parts like the ID_GET / ID_RESP for resolving
+ * the UNIT ID, as well as the keepalive ping/pong messages.  Furthermore, the
+ * Stream Identifiers are fixed on the BTS side (RSL always 0, OML always 0xff)
+ * and both OML+RSL share a single TCP connection.
+ *
+ * Other oddities include the encapsulation of BSSGP messages in the L3_INFO IE
+ * of RSL
+ */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <time.h>
+#include <sys/fcntl.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <arpa/inet.h>
+
+#include <osmocore/select.h>
+#include <osmocore/tlv.h>
+#include <osmocore/msgb.h>
+#include <openbsc/debug.h>
+#include <openbsc/gsm_data.h>
+#include <openbsc/abis_nm.h>
+#include <openbsc/abis_rsl.h>
+#include <openbsc/subchan_demux.h>
+#include <openbsc/e1_input.h>
+#include <openbsc/ipaccess.h>
+#include <openbsc/socket.h>
+#include <openbsc/signal.h>
+#include <osmocore/talloc.h>
+
+#define HSL_TCP_PORT	2500
+#define HSL_PROTO_DEBUG	0xdd
+
+#define PRIV_OML 1
+#define PRIV_RSL 2
+
+/* data structure for one E1 interface with A-bis */
+struct hsl_e1_handle {
+	struct bsc_fd listen_fd;
+	struct gsm_network *gsmnet;
+};
+
+static struct hsl_e1_handle *e1h;
+
+
+#define TS1_ALLOC_SIZE	900
+
+#define OML_UP		0x0001
+#define RSL_UP		0x0002
+
+int hsl_drop_oml(struct gsm_bts *bts)
+{
+	struct gsm_bts_trx *trx;
+	struct e1inp_ts *ts;
+	struct e1inp_line *line;
+	struct bsc_fd *bfd;
+
+	if (!bts || !bts->oml_link)
+		return -1;
+
+	/* send OML down */
+	ts = bts->oml_link->ts;
+	line = ts->line;
+	e1inp_event(ts, S_INP_TEI_DN, bts->oml_link->tei, bts->oml_link->sapi);
+
+	bfd = &ts->driver.ipaccess.fd;
+	bsc_unregister_fd(bfd);
+	close(bfd->fd);
+	bfd->fd = -1;
+
+	/* clean up OML and RSL */
+	e1inp_sign_link_destroy(bts->oml_link);
+	bts->oml_link = NULL;
+	e1inp_sign_link_destroy(bts->c0->rsl_link);
+	bts->c0->rsl_link = NULL;
+	bts->ip_access.flags = 0;
+
+	/* kill the E1 line now... as we have no one left to use it */
+	talloc_free(line);
+
+	return -1;
+}
+
+static int hsl_drop_ts_fd(struct e1inp_ts *ts, struct bsc_fd *bfd)
+{
+	struct e1inp_sign_link *link, *link2;
+	int bts_nr = -1;
+
+	llist_for_each_entry_safe(link, link2, &ts->sign.sign_links, list) {
+		bts_nr = link->trx->bts->bts_nr;
+		e1inp_sign_link_destroy(link);
+	}
+
+	bsc_unregister_fd(bfd);
+	close(bfd->fd);
+	bfd->fd = -1;
+
+	talloc_free(ts->line);
+
+	return bts_nr;
+}
+
+struct gsm_bts *find_bts_by_serno(struct gsm_network *net, unsigned long serno)
+{
+	struct gsm_bts *bts;
+
+	llist_for_each_entry(bts, &net->bts_list, list) {
+		if (bts->type != GSM_BTS_TYPE_HSL_FEMTO)
+			continue;
+
+		if (serno == bts->hsl.serno)
+			return bts;
+	}
+
+	return NULL;
+}
+
+
+static int process_hsl_rsl(struct msgb *msg, struct e1inp_line *line)
+{
+	char serno_buf[16];
+	uint8_t serno_len;
+	unsigned long serno;
+	struct gsm_bts *bts;
+
+	switch (msg->l2h[1]) {
+	case 0x80:
+		/*, contains Serial Number + SW version */
+		if (msg->l2h[2] != 0xc0)
+			break;
+		serno_len = msg->l2h[3];
+		if (serno_len > sizeof(serno_buf)-1)
+			serno_len = sizeof(serno_buf)-1;
+		memcpy(serno_buf, msg->l2h+4, serno_len);
+		serno_buf[serno_len] = '\0';
+		serno = strtoul(serno_buf, NULL, 10);
+		bts = find_bts_by_serno(e1h->gsmnet, serno);
+		if (!bts) {
+			LOGP(DINP, LOGL_ERROR, "Unable to find BTS config for "
+				"serial number %lu(%s)\n", serno, serno_buf);
+			return -EIO;
+		}
+
+		DEBUGP(DINP, "Identified HSL BTS Serial Number %lu\n", serno);
+
+		/* we shouldn't hardcode it, but HSL femto also hardcodes it... */
+		bts->oml_tei = 255;
+		bts->c0->rsl_tei = 0;
+		bts->oml_link = e1inp_sign_link_create(&line->ts[PRIV_OML - 1],
+							E1INP_SIGN_OML, bts->c0,
+							bts->oml_tei, 0);
+		bts->c0->rsl_link = e1inp_sign_link_create(&line->ts[PRIV_OML - 1],
+							E1INP_SIGN_RSL, bts->c0,
+							bts->c0->rsl_tei, 0);
+		e1inp_event(&line->ts[PRIV_OML-1], S_INP_TEI_UP, 255, 0);
+		e1inp_event(&line->ts[PRIV_OML-1], S_INP_TEI_UP, 0, 0);
+		bts->ip_access.flags |= OML_UP;
+		bts->ip_access.flags |= (RSL_UP << 0);
+		msgb_free(msg);
+		return 1;	/* == we have taken over the msg */
+	case 0x82:
+		/* FIXME: do something with BSSGP, i.e. forward it over
+		 * NSIP to OsmoSGSN */
+		return 0;
+	}
+	return 0;
+}
+
+static int handle_ts1_read(struct bsc_fd *bfd)
+{
+	struct e1inp_line *line = bfd->data;
+	unsigned int ts_nr = bfd->priv_nr;
+	struct e1inp_ts *e1i_ts = &line->ts[ts_nr-1];
+	struct e1inp_sign_link *link;
+	struct msgb *msg;
+	struct ipaccess_head *hh;
+	int ret = 0, error;
+
+	msg = ipaccess_read_msg(bfd, &error);
+	if (!msg) {
+		if (error == 0) {
+			int ret = hsl_drop_ts_fd(e1i_ts, bfd);
+			if (ret >= 0)
+				LOGP(DINP, LOGL_NOTICE, "BTS %u disappeared, dead socket\n",
+					ret);
+			else
+				LOGP(DINP, LOGL_NOTICE, "unknown BTS disappeared, dead socket\n");
+		}
+		return error;
+	}
+
+	DEBUGP(DMI, "RX %u: %s\n", ts_nr, hexdump(msgb_l2(msg), msgb_l2len(msg)));
+
+	hh = (struct ipaccess_head *) msg->data;
+	if (hh->proto == HSL_PROTO_DEBUG) {
+		LOGP(DINP, LOGL_NOTICE, "HSL debug: %s\n", msg->data + sizeof(*hh));
+		msgb_free(msg);
+		return ret;
+	}
+
+	/* HSL proprietary RSL extension */
+	if (hh->proto == 0 && msg->l2h[0] == 0x80) {
+		ret = process_hsl_rsl(msg, line);
+		if (ret < 0) {
+			/* FIXME: close connection */
+			hsl_drop_ts_fd(e1i_ts, bfd);
+			return ret;
+		} else if (ret == 1)
+			return 0;
+		/* else: continue... */
+	}
+
+	/* HSL for whatever reason chose to use 0x81 instead of 0x80 for FOM */
+	if (hh->proto == 255 && msg->l2h[0] == (ABIS_OM_MDISC_FOM | 0x01))
+		msg->l2h[0] = ABIS_OM_MDISC_FOM;
+
+	link = e1inp_lookup_sign_link(e1i_ts, hh->proto, 0);
+	if (!link) {
+		LOGP(DINP, LOGL_ERROR, "no matching signalling link for "
+			"hh->proto=0x%02x\n", hh->proto);
+		msgb_free(msg);
+		return -EIO;
+	}
+	msg->trx = link->trx;
+
+	switch (link->type) {
+	case E1INP_SIGN_RSL:
+		if (!(msg->trx->bts->ip_access.flags & (RSL_UP << msg->trx->nr))) {
+			e1inp_event(e1i_ts, S_INP_TEI_UP, link->tei, link->sapi);
+			msg->trx->bts->ip_access.flags |= (RSL_UP << msg->trx->nr);
+		}
+		ret = abis_rsl_rcvmsg(msg);
+		break;
+	case E1INP_SIGN_OML:
+		if (!(msg->trx->bts->ip_access.flags & OML_UP)) {
+			e1inp_event(e1i_ts, S_INP_TEI_UP, link->tei, link->sapi);
+			msg->trx->bts->ip_access.flags |= OML_UP;
+		}
+		ret = abis_nm_rcvmsg(msg);
+		break;
+	default:
+		LOGP(DINP, LOGL_NOTICE, "Unknown HSL protocol class 0x%02x\n", hh->proto);
+		msgb_free(msg);
+		break;
+	}
+	return ret;
+}
+
+static int ts_want_write(struct e1inp_ts *e1i_ts)
+{
+	e1i_ts->driver.ipaccess.fd.when |= BSC_FD_WRITE;
+
+	return 0;
+}
+
+static void timeout_ts1_write(void *data)
+{
+	struct e1inp_ts *e1i_ts = (struct e1inp_ts *)data;
+
+	/* trigger write of ts1, due to tx delay timer */
+	ts_want_write(e1i_ts);
+}
+
+static int handle_ts1_write(struct bsc_fd *bfd)
+{
+	struct e1inp_line *line = bfd->data;
+	unsigned int ts_nr = bfd->priv_nr;
+	struct e1inp_ts *e1i_ts = &line->ts[ts_nr-1];
+	struct e1inp_sign_link *sign_link;
+	struct msgb *msg;
+	u_int8_t proto;
+	int ret;
+
+	bfd->when &= ~BSC_FD_WRITE;
+
+	/* get the next msg for this timeslot */
+	msg = e1inp_tx_ts(e1i_ts, &sign_link);
+	if (!msg) {
+		/* no message after tx delay timer */
+		return 0;
+	}
+
+	switch (sign_link->type) {
+	case E1INP_SIGN_OML:
+		proto = IPAC_PROTO_OML;
+		/* HSL uses 0x81 for FOM for some reason */
+		if (msg->data[0] == ABIS_OM_MDISC_FOM)
+			msg->data[0] = ABIS_OM_MDISC_FOM | 0x01;
+		break;
+	case E1INP_SIGN_RSL:
+		proto = IPAC_PROTO_RSL;
+		break;
+	default:
+		msgb_free(msg);
+		bfd->when |= BSC_FD_WRITE; /* come back for more msg */
+		return -EINVAL;
+	}
+
+	msg->l2h = msg->data;
+	ipaccess_prepend_header(msg, sign_link->tei);
+
+	DEBUGP(DMI, "TX %u: %s\n", ts_nr, hexdump(msg->l2h, msgb_l2len(msg)));
+
+	ret = send(bfd->fd, msg->data, msg->len, 0);
+	msgb_free(msg);
+
+	/* set tx delay timer for next event */
+	e1i_ts->sign.tx_timer.cb = timeout_ts1_write;
+	e1i_ts->sign.tx_timer.data = e1i_ts;
+
+	/* Reducing this might break the nanoBTS 900 init. */
+	bsc_schedule_timer(&e1i_ts->sign.tx_timer, 0, e1i_ts->sign.delay);
+
+	return ret;
+}
+
+/* callback from select.c in case one of the fd's can be read/written */
+static int hsl_fd_cb(struct bsc_fd *bfd, unsigned int what)
+{
+	struct e1inp_line *line = bfd->data;
+	unsigned int ts_nr = bfd->priv_nr;
+	unsigned int idx = ts_nr-1;
+	struct e1inp_ts *e1i_ts;
+	int rc = 0;
+
+	/* In case of early RSL we might not yet have a line */
+
+	if (line)
+		e1i_ts = &line->ts[idx];
+
+	if (!line || e1i_ts->type == E1INP_TS_TYPE_SIGN) {
+		if (what & BSC_FD_READ)
+			rc = handle_ts1_read(bfd);
+		if (what & BSC_FD_WRITE)
+			rc = handle_ts1_write(bfd);
+	} else
+		LOGP(DINP, LOGL_ERROR, "unknown E1 TS type %u\n", e1i_ts->type);
+
+	return rc;
+}
+
+struct e1inp_driver hsl_driver = {
+	.name = "HSL",
+	.want_write = ts_want_write,
+	.default_delay = 0,
+};
+
+/* callback of the OML listening filedescriptor */
+static int listen_fd_cb(struct bsc_fd *listen_bfd, unsigned int what)
+{
+	int ret;
+	int idx = 0;
+	int i;
+	struct e1inp_line *line;
+	struct e1inp_ts *e1i_ts;
+	struct bsc_fd *bfd;
+	struct sockaddr_in sa;
+	socklen_t sa_len = sizeof(sa);
+
+	if (!(what & BSC_FD_READ))
+		return 0;
+
+	ret = accept(listen_bfd->fd, (struct sockaddr *) &sa, &sa_len);
+	if (ret < 0) {
+		perror("accept");
+		return ret;
+	}
+	LOGP(DINP, LOGL_NOTICE, "accept()ed new HSL link from %s\n",
+		inet_ntoa(sa.sin_addr));
+
+	line = talloc_zero(tall_bsc_ctx, struct e1inp_line);
+	if (!line) {
+		close(ret);
+		return -ENOMEM;
+	}
+	line->driver = &hsl_driver;
+	//line->driver_data = e1h;
+	/* create virrtual E1 timeslots for signalling */
+	e1inp_ts_config(&line->ts[1-1], line, E1INP_TS_TYPE_SIGN);
+
+	/* initialize the fds */
+	for (i = 0; i < ARRAY_SIZE(line->ts); ++i)
+		line->ts[i].driver.ipaccess.fd.fd = -1;
+
+	e1i_ts = &line->ts[idx];
+
+	bfd = &e1i_ts->driver.ipaccess.fd;
+	bfd->fd = ret;
+	bfd->data = line;
+	bfd->priv_nr = PRIV_OML;
+	bfd->cb = hsl_fd_cb;
+	bfd->when = BSC_FD_READ;
+	ret = bsc_register_fd(bfd);
+	if (ret < 0) {
+		LOGP(DINP, LOGL_ERROR, "could not register FD\n");
+		close(bfd->fd);
+		talloc_free(line);
+		return ret;
+	}
+
+        return ret;
+	//return e1inp_line_register(line);
+}
+
+int hsl_setup(struct gsm_network *gsmnet)
+{
+	int ret;
+
+	/* register the driver with the core */
+	/* FIXME: do this in the plugin initializer function */
+	ret = e1inp_driver_register(&hsl_driver);
+	if (ret)
+		return ret;
+
+	e1h = talloc_zero(tall_bsc_ctx, struct hsl_e1_handle);
+	if (!e1h)
+		return -ENOMEM;
+
+	e1h->gsmnet = gsmnet;
+
+	/* Listen for connections */
+	ret = make_sock(&e1h->listen_fd, IPPROTO_TCP, 0, HSL_TCP_PORT,
+			listen_fd_cb);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}