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The application which initializes the n_gsm ldisc may like to set individual default parameters for each DLCI or take over of the application specific DLCI configuration completely. This is currently not possible. It is either possible to set common default parameters for all DLCIs or let the user application set its DLCI specific configuration parameters. Add support of GSMIOC_GETCONF_DLCI and GSMIOC_SETCONF_DLCI for the n_gsm ldisc handle to support DLCI specific parameter configuration upfront. Add a code example for this use case to the n_gsm documentation. Signed-off-by: Daniel Starke <daniel.starke@siemens.com> Link: https://lore.kernel.org/r/20230315105354.6234-3-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
192 lines
6.1 KiB
ReStructuredText
192 lines
6.1 KiB
ReStructuredText
==============================
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GSM 0710 tty multiplexor HOWTO
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==============================
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.. contents:: :local:
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This line discipline implements the GSM 07.10 multiplexing protocol
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detailed in the following 3GPP document:
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https://www.3gpp.org/ftp/Specs/archive/07_series/07.10/0710-720.zip
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This document give some hints on how to use this driver with GPRS and 3G
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modems connected to a physical serial port.
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How to use it
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=============
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Config Initiator
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----------------
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#. Initialize the modem in 0710 mux mode (usually ``AT+CMUX=`` command) through
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its serial port. Depending on the modem used, you can pass more or less
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parameters to this command.
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#. Switch the serial line to using the n_gsm line discipline by using
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``TIOCSETD`` ioctl.
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#. Configure the mux using ``GSMIOC_GETCONF_EXT``/``GSMIOC_SETCONF_EXT`` ioctl if needed.
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#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.
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#. Configure DLCs using ``GSMIOC_GETCONF_DLCI``/``GSMIOC_SETCONF_DLCI`` ioctl for non-defaults.
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#. Obtain base gsmtty number for the used serial port.
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Major parts of the initialization program
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(a good starting point is util-linux-ng/sys-utils/ldattach.c)::
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#include <stdio.h>
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#include <stdint.h>
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#include <linux/gsmmux.h>
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#include <linux/tty.h>
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#define DEFAULT_SPEED B115200
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#define SERIAL_PORT /dev/ttyS0
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int ldisc = N_GSM0710;
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struct gsm_config c;
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struct gsm_config_ext ce;
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struct gsm_dlci_config dc;
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struct termios configuration;
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uint32_t first;
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/* open the serial port connected to the modem */
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fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
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/* configure the serial port : speed, flow control ... */
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/* send the AT commands to switch the modem to CMUX mode
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and check that it's successful (should return OK) */
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write(fd, "AT+CMUX=0\r", 10);
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/* experience showed that some modems need some time before
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being able to answer to the first MUX packet so a delay
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may be needed here in some case */
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sleep(3);
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/* use n_gsm line discipline */
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ioctl(fd, TIOCSETD, &ldisc);
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/* get n_gsm extended configuration */
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ioctl(fd, GSMIOC_GETCONF_EXT, &ce);
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/* use keep-alive once every 5s for modem connection supervision */
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ce.keep_alive = 500;
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/* set the new extended configuration */
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ioctl(fd, GSMIOC_SETCONF_EXT, &ce);
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/* get n_gsm configuration */
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ioctl(fd, GSMIOC_GETCONF, &c);
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/* we are initiator and need encoding 0 (basic) */
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c.initiator = 1;
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c.encapsulation = 0;
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/* our modem defaults to a maximum size of 127 bytes */
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c.mru = 127;
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c.mtu = 127;
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/* set the new configuration */
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ioctl(fd, GSMIOC_SETCONF, &c);
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/* get DLC 1 configuration */
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dc.channel = 1;
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ioctl(fd, GSMIOC_GETCONF_DLCI, &dc);
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/* the first user channel gets a higher priority */
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dc.priority = 1;
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/* set the new DLC 1 specific configuration */
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ioctl(fd, GSMIOC_SETCONF_DLCI, &dc);
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/* get first gsmtty device node */
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ioctl(fd, GSMIOC_GETFIRST, &first);
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printf("first muxed line: /dev/gsmtty%i\n", first);
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/* and wait for ever to keep the line discipline enabled */
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daemon(0,0);
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pause();
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#. Use these devices as plain serial ports.
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For example, it's possible:
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- to use *gnokii* to send / receive SMS on ``ttygsm1``
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- to use *ppp* to establish a datalink on ``ttygsm2``
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#. First close all virtual ports before closing the physical port.
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Note that after closing the physical port the modem is still in multiplexing
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mode. This may prevent a successful re-opening of the port later. To avoid
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this situation either reset the modem if your hardware allows that or send
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a disconnect command frame manually before initializing the multiplexing mode
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for the second time. The byte sequence for the disconnect command frame is::
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0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9
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Config Requester
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----------------
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#. Receive ``AT+CMUX=`` command through its serial port, initialize mux mode
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config.
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#. Switch the serial line to using the *n_gsm* line discipline by using
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``TIOCSETD`` ioctl.
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#. Configure the mux using ``GSMIOC_GETCONF_EXT``/``GSMIOC_SETCONF_EXT``
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ioctl if needed.
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#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.
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#. Configure DLCs using ``GSMIOC_GETCONF_DLCI``/``GSMIOC_SETCONF_DLCI`` ioctl for non-defaults.
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#. Obtain base gsmtty number for the used serial port::
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#include <stdio.h>
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#include <stdint.h>
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#include <linux/gsmmux.h>
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#include <linux/tty.h>
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#define DEFAULT_SPEED B115200
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#define SERIAL_PORT /dev/ttyS0
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int ldisc = N_GSM0710;
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struct gsm_config c;
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struct gsm_config_ext ce;
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struct gsm_dlci_config dc;
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struct termios configuration;
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uint32_t first;
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/* open the serial port */
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fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
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/* configure the serial port : speed, flow control ... */
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/* get serial data and check "AT+CMUX=command" parameter ... */
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/* use n_gsm line discipline */
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ioctl(fd, TIOCSETD, &ldisc);
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/* get n_gsm extended configuration */
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ioctl(fd, GSMIOC_GETCONF_EXT, &ce);
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/* use keep-alive once every 5s for peer connection supervision */
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ce.keep_alive = 500;
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/* set the new extended configuration */
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ioctl(fd, GSMIOC_SETCONF_EXT, &ce);
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/* get n_gsm configuration */
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ioctl(fd, GSMIOC_GETCONF, &c);
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/* we are requester and need encoding 0 (basic) */
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c.initiator = 0;
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c.encapsulation = 0;
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/* our modem defaults to a maximum size of 127 bytes */
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c.mru = 127;
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c.mtu = 127;
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/* set the new configuration */
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ioctl(fd, GSMIOC_SETCONF, &c);
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/* get DLC 1 configuration */
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dc.channel = 1;
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ioctl(fd, GSMIOC_GETCONF_DLCI, &dc);
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/* the first user channel gets a higher priority */
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dc.priority = 1;
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/* set the new DLC 1 specific configuration */
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ioctl(fd, GSMIOC_SETCONF_DLCI, &dc);
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/* get first gsmtty device node */
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ioctl(fd, GSMIOC_GETFIRST, &first);
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printf("first muxed line: /dev/gsmtty%i\n", first);
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/* and wait for ever to keep the line discipline enabled */
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daemon(0,0);
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pause();
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11-03-08 - Eric Bénard - <eric@eukrea.com>
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