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authorMartin Hundebøll <martin@geanix.com>2019-08-12 23:12:43 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-09-04 12:43:54 +0200
commita7b121b4b8b0bcc14fc1c2a81d34096109a65dd6 (patch)
tree19c00636e4d396d430f254ad841f4226134b6f30 /Documentation/driver-api/serial
parentd193db7fb10d3ae8322e5f65e4c39946156e24c2 (diff)
tty: n_gsm: add ioctl to map serial device to mux'ed tty
Guessing the first 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 an ioctl. Signed-off-by: Martin Hundebøll <martin@geanix.com> Link: https://lore.kernel.org/r/20190812211243.98686-1-martin@geanix.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/driver-api/serial')
-rw-r--r--Documentation/driver-api/serial/n_gsm.rst11
1 files changed, 9 insertions, 2 deletions
diff --git a/Documentation/driver-api/serial/n_gsm.rst b/Documentation/driver-api/serial/n_gsm.rst
index 0ba731ab00b2..286e7ff4d2d9 100644
--- a/Documentation/driver-api/serial/n_gsm.rst
+++ b/Documentation/driver-api/serial/n_gsm.rst
@@ -18,10 +18,13 @@ 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 <stdint.h>
#include <linux/gsmmux.h>
#include <linux/tty.h>
#define DEFAULT_SPEED B115200
@@ -30,6 +33,7 @@ Major parts of the initialization program :
int ldisc = N_GSM0710;
struct gsm_config c;
struct termios configuration;
+ uint32_t first;
/* open the serial port connected to the modem */
fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
@@ -58,19 +62,22 @@ Major parts of the initialization program :
c.mtu = 127;
/* set the new configuration */
ioctl(fd, GSMIOC_SETCONF, &c);
+ /* get first gsmtty device node */
+ ioctl(fd, GSMIOC_GETFIRST, &first);
+ printf("first muxed line: /dev/gsmtty%i\n", first);
/* and wait for ever to keep the line discipline enabled */
daemon(0,0);
pause();
-4. use these devices as plain serial ports.
+5. use these devices as plain serial ports.
for example, it's possible:
- and to use gnokii to send / receive SMS on ttygsm1
- to use ppp to establish a datalink on ttygsm2
-5. first close all virtual ports before closing the physical port.
+6. first close all virtual ports before closing the physical port.
Note that after closing the physical port the modem is still in multiplexing
mode. This may prevent a successful re-opening of the port later. To avoid