Guessing the base tty for a gsm0710 multiplexed serial device is not
currently possible, which makes it racy to use with multiple modems.
Add a way to map the physical serial tty to its related mux devices
using a ioctl.
Signed-off-by: Martin Hundebøll <mar...@geanix.com>
---
Documentation/serial/n_gsm.rst | 8 ++++++++
drivers/tty/n_gsm.c | 6 ++++++
include/uapi/linux/gsmmux.h | 2 ++
3 files changed, 16 insertions(+)
diff --git a/Documentation/serial/n_gsm.rst b/Documentation/serial/n_gsm.rst
index a3ce1b269018..bf5d7f82b5af 100644
--- a/Documentation/serial/n_gsm.rst
+++ b/Documentation/serial/n_gsm.rst
@@ -18,10 +18,12 @@ How to use it
2. switch the serial line to using the n_gsm line discipline by using
TIOCSETD ioctl,
3. configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl,
+4. obtain base gsmtty number for the used serial port,
Major parts of the initialization program :
(a good starting point is util-linux-ng/sys-utils/ldattach.c)::
+ #include <stdio.h>
#include <linux/gsmmux.h>
#include <linux/tty.h>
#define DEFAULT_SPEED B115200
@@ -30,6 +32,7 @@ Major parts of the initialization program :
int ldisc = N_GSM0710;
struct gsm_config c;
struct termios configuration;
+ int base;
/* open the serial port connected to the modem */
fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
@@ -58,6 +61,11 @@ Major parts of the initialization program :
c.mtu = 127;
/* set the new configuration */
ioctl(fd, GSMIOC_SETCONF, &c);
+ /* get and print base gsmtty device node */
+ ioctl(fd, GSMIOC_GETBASE, &base);
+ /* the base node is used for mux control by the driver */
+ printf(first muxed line: /dev/gsmtty%i\n", base + 1);
+
/* and wait for ever to keep the line discipline enabled */
daemon(0,0);
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index cba06063c44a..93c24d9b582b 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2612,6 +2612,7 @@ static int gsmld_ioctl(struct tty_struct *tty, struct
file *file,
{
struct gsm_config c;
struct gsm_mux *gsm = tty->disc_data;
+ int base;
switch (cmd) {
case GSMIOC_GETCONF:
@@ -2623,6 +2624,11 @@ static int gsmld_ioctl(struct tty_struct *tty, struct
file *file,
if (copy_from_user(&c, (void *)arg, sizeof(c)))
return -EFAULT;
return gsm_config(gsm, &c);
+ case GSMIOC_GETBASE:
+ base = mux_num_to_base(gsm);
+ if (copy_to_user((void *)arg, &base, sizeof(base)))
+ return -EFAULT;
+ return 0;
default:
return n_tty_ioctl_helper(tty, file, cmd, arg);
}
diff --git a/include/uapi/linux/gsmmux.h b/include/uapi/linux/gsmmux.h
index 101d3c469acb..6eb63be3ed9e 100644
--- a/include/uapi/linux/gsmmux.h
+++ b/include/uapi/linux/gsmmux.h
@@ -37,5 +37,7 @@ struct gsm_netconfig {
#define GSMIOC_ENABLE_NET _IOW('G', 2, struct gsm_netconfig)
#define GSMIOC_DISABLE_NET _IO('G', 3)
+/* get the base tty number for a configured gsmmux tty */
+#define GSMIOC_GETBASE _IOR('G', 4, int)
#endif
--
2.22.0
