dahdi: Use ioctl(DAHDI_SPECIFY) instead of legacy /dev/dahdi/%u

It appears that opening "/dev/dahdi/channel" and using
ioctl(DAHDI_SPECIFY) is possible at least since dahdi 2.4 (from 2010),
and opening "/dev/dahdi/%u" has been deprecated ever since.  One
advantage of the new interface is that you can use channel numbers
larger than 250, which is quite easily possible if you have more than
eight E1 lines on a system.  It also makes libosmo-abis work on systems
where there are no udev rules for creating the legacy device nodes.

Change-Id: Id6c8f27d7ae948b50e9cf5a38f039d782ff78e1d

1 files changed, 35 insertions, 26 deletions

diff --git a/src/input/dahdi.c b/src/input/dahdi.c
index 47276a7..6594eea 100644
--- a/src/input/dahdi.c
+++ b/src/input/dahdi.c
@@ -1,6 +1,6 @@
 /* OpenBSC Abis input driver for DAHDI */
 
-/* (C) 2008-2011 by Harald Welte <laforge@gnumonks.org>
+/* (C) 2008-2019 by Harald Welte <laforge@gnumonks.org>
  * (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
  * (C) 2010 by Digium and Matthew Fredrickson <creslin@digium.com>
  *
@@ -603,6 +603,33 @@ int dahdi_set_bufinfo(int fd, int as_sigchan)
 	return 0;
 }
 
+static int dahdi_open_slot(int dahdi_chan_nr)
+{
+	int rc, fd;
+#ifndef DAHDI_SPECIFY
+	char openstr[128];
+	snprintf(openstr, sizeof(openstr), "/dev/dahdi/%d", dev_nr);
+#else
+	const char *openstr = "/dev/dahdi/channel";
+#endif
+	rc = open(openstr, O_RDWR | O_NONBLOCK);
+	if (rc < 0) {
+		LOGP(DLINP, LOGL_ERROR, "DAHDI: could not open %s %s\n", openstr, strerror(errno));
+		return -EIO;
+	}
+	fd = rc;
+#ifdef DAHDI_SPECIFY
+	rc = ioctl(fd, DAHDI_SPECIFY, &dahdi_chan_nr);
+	if (rc < 0) {
+		close(fd);
+		LOGP(DLINP, LOGL_ERROR, "DAHDI: could not DAHDI_SPECIFY %d: %s\n",
+		     dahdi_chan_nr, strerror(errno));
+		return -EIO;
+	}
+#endif
+	return fd;
+}
+
 static int dahdi_e1_setup(struct e1inp_line *line)
 {
 	struct span_cfg *scfg;
@@ -623,7 +650,6 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 	/* TS0 is CRC4, don't need any fd for it */
 	for (ts = 1; ts <= scfg->chan_num; ts++) {
 		unsigned int idx = ts-1;
-		char openstr[128];
 		struct e1inp_ts *e1i_ts = &line->ts[idx];
 		struct osmo_fd *bfd = &e1i_ts->driver.dahdi.fd;
 		int dev_nr;
@@ -640,7 +666,6 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 		bfd->data = line;
 		bfd->priv_nr = ts;
 		bfd->cb = dahdi_fd_cb;
-		snprintf(openstr, sizeof(openstr), "/dev/dahdi/%d", dev_nr);
 
 		switch (e1i_ts->type) {
 		case E1INP_TS_TYPE_NONE:
@@ -657,13 +682,9 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 			break;
 		case E1INP_TS_TYPE_SIGN:
 			if (!bfd->fd)
-				bfd->fd = open(openstr, O_RDWR | O_NONBLOCK);
-			if (bfd->fd == -1) {
-				LOGP(DLINP, LOGL_ERROR,
-					"%s could not open %s %s\n",
-					__func__, openstr, strerror(errno));
+				bfd->fd = dahdi_open_slot(dev_nr);
+			if (bfd->fd < 0)
 				return -EIO;
-			}
 			bfd->when = BSC_FD_READ | BSC_FD_EXCEPT;
 			ret = dahdi_set_bufinfo(bfd->fd, 1);
 			if (ret < 0)
@@ -676,13 +697,9 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 			break;
 		case E1INP_TS_TYPE_HDLC:
 			if (!bfd->fd)
-				bfd->fd = open(openstr, O_RDWR | O_NONBLOCK);
-			if (bfd->fd == -1) {
-				LOGP(DLINP, LOGL_ERROR,
-					"%s could not open %s %s\n",
-					__func__, openstr, strerror(errno));
+				bfd->fd = dahdi_open_slot(dev_nr);
+			if (bfd->fd < 0)
 				return -EIO;
-			}
 			bfd->when = BSC_FD_READ | BSC_FD_EXCEPT;
 			ret = dahdi_set_bufinfo(bfd->fd, 1);
 			if (ret < 0)
@@ -696,13 +713,9 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 				e1i_ts->lapd = NULL;
 			}
 			if (!bfd->fd)
-				bfd->fd = open(openstr, O_RDWR | O_NONBLOCK);
-			if (bfd->fd == -1) {
-				LOGP(DLINP, LOGL_ERROR,
-					"%s could not open %s %s\n",
-					__func__, openstr, strerror(errno));
+				bfd->fd = dahdi_open_slot(dev_nr);
+			if (bfd->fd < 0)
 				return -EIO;
-			}
 			ret = dahdi_set_bufinfo(bfd->fd, 0);
 			if (ret < 0)
 				return -EIO;
@@ -713,12 +726,8 @@ static int dahdi_e1_setup(struct e1inp_line *line)
 			break;
 		}
 
-		if (bfd->fd < 0) {
-			LOGP(DLINP, LOGL_ERROR,
-				"%s could not open %s %s\n",
-				__func__, openstr, strerror(errno));
+		if (bfd->fd < 0)
 			return bfd->fd;
-		}
 
 		ret = osmo_fd_register(bfd);
 		if (ret < 0) {