[PATCH 6/6] Documentation: tty: n_gsm, use power of ReST

From: Jiri Slaby
Date: Mon Apr 11 2022 - 07:02:18 EST


Reformat the whole document, so that automatic numbering and TOC is
properly generated.

Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
Documentation/driver-api/tty/n_gsm.rst | 144 +++++++++++++------------
1 file changed, 74 insertions(+), 70 deletions(-)

diff --git a/Documentation/driver-api/tty/n_gsm.rst b/Documentation/driver-api/tty/n_gsm.rst
index 04308a7a194a..35d7381515b0 100644
--- a/Documentation/driver-api/tty/n_gsm.rst
+++ b/Documentation/driver-api/tty/n_gsm.rst
@@ -2,6 +2,8 @@
GSM 0710 tty multiplexor HOWTO
==============================

+.. contents:: :local:
+
This line discipline implements the GSM 07.10 multiplexing protocol
detailed in the following 3GPP document:

@@ -11,79 +13,81 @@ This document give some hints on how to use this driver with GPRS and 3G
modems connected to a physical serial port.

How to use it
--------------
-1. config initiator
-^^^^^^^^^^^^^^^^^^^^^
+=============

-1.1 initialize the modem in 0710 mux mode (usually AT+CMUX= command) through
- its serial port. Depending on the modem used, you can pass more or less
- parameters to this command.
+Config Initiator
+----------------

-1.2 switch the serial line to using the n_gsm line discipline by using
- TIOCSETD ioctl.
+#. Initialize the modem in 0710 mux mode (usually ``AT+CMUX=`` command) through
+ its serial port. Depending on the modem used, you can pass more or less
+ parameters to this command.

-1.3 configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl.
+#. Switch the serial line to using the n_gsm line discipline by using
+ ``TIOCSETD`` ioctl.

-1.4 obtain base gsmtty number for the used serial port.
+#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.

-Major parts of the initialization program :
-(a good starting point is util-linux-ng/sys-utils/ldattach.c)::
+#. Obtain base gsmtty number for the used serial port.

- #include <stdio.h>
- #include <stdint.h>
- #include <linux/gsmmux.h>
- #include <linux/tty.h>
- #define DEFAULT_SPEED B115200
- #define SERIAL_PORT /dev/ttyS0
+ Major parts of the initialization program
+ (a good starting point is util-linux-ng/sys-utils/ldattach.c)::

- int ldisc = N_GSM0710;
- struct gsm_config c;
- struct termios configuration;
- uint32_t first;
+ #include <stdio.h>
+ #include <stdint.h>
+ #include <linux/gsmmux.h>
+ #include <linux/tty.h>

- /* open the serial port connected to the modem */
- fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
+ #define DEFAULT_SPEED B115200
+ #define SERIAL_PORT /dev/ttyS0

- /* configure the serial port : speed, flow control ... */
+ int ldisc = N_GSM0710;
+ struct gsm_config c;
+ struct termios configuration;
+ uint32_t first;

- /* send the AT commands to switch the modem to CMUX mode
- and check that it's successful (should return OK) */
- write(fd, "AT+CMUX=0\r", 10);
+ /* open the serial port connected to the modem */
+ fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);

- /* experience showed that some modems need some time before
- being able to answer to the first MUX packet so a delay
- may be needed here in some case */
- sleep(3);
+ /* configure the serial port : speed, flow control ... */

- /* use n_gsm line discipline */
- ioctl(fd, TIOCSETD, &ldisc);
+ /* send the AT commands to switch the modem to CMUX mode
+ and check that it's successful (should return OK) */
+ write(fd, "AT+CMUX=0\r", 10);

- /* get n_gsm configuration */
- ioctl(fd, GSMIOC_GETCONF, &c);
- /* we are initiator and need encoding 0 (basic) */
- c.initiator = 1;
- c.encapsulation = 0;
- /* our modem defaults to a maximum size of 127 bytes */
- c.mru = 127;
- 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);
+ /* experience showed that some modems need some time before
+ being able to answer to the first MUX packet so a delay
+ may be needed here in some case */
+ sleep(3);

- /* and wait for ever to keep the line discipline enabled */
- daemon(0,0);
- pause();
+ /* use n_gsm line discipline */
+ ioctl(fd, TIOCSETD, &ldisc);
+
+ /* get n_gsm configuration */
+ ioctl(fd, GSMIOC_GETCONF, &c);
+ /* we are initiator and need encoding 0 (basic) */
+ c.initiator = 1;
+ c.encapsulation = 0;
+ /* our modem defaults to a maximum size of 127 bytes */
+ c.mru = 127;
+ 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();

-1.5 use these devices as plain serial ports.
+#. Use these devices as plain serial ports.

- for example, it's possible:
+ For example, it's possible:

- - and to use gnokii to send / receive SMS on ttygsm1
- - to use ppp to establish a datalink on ttygsm2
+ - to use *gnokii* to send / receive SMS on ``ttygsm1``
+ - to use *ppp* to establish a datalink on ``ttygsm2``

-1.6 first close all virtual ports before closing the physical port.
+#. 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
@@ -91,27 +95,27 @@ Major parts of the initialization program :
a disconnect command frame manually before initializing the multiplexing mode
for the second time. The byte sequence for the disconnect command frame is::

- 0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9.
+ 0xf9, 0x03, 0xef, 0x03, 0xc3, 0x16, 0xf9

-2. config requester
-^^^^^^^^^^^^^^^^^^^^^
+Config Requester
+----------------

-2.1 receive string "AT+CMUX= command" through its serial port,initialize
- mux mode config
+#. Receive ``AT+CMUX=`` command through its serial port, initialize mux mode
+ config.

-2.2 switch the serial line to using the n_gsm line discipline by using
- TIOCSETD ioctl.
+#. Switch the serial line to using the *n_gsm* line discipline by using
+ ``TIOCSETD`` ioctl.

-2.3 configure the mux using GSMIOC_GETCONF / GSMIOC_SETCONF ioctl.
+#. Configure the mux using ``GSMIOC_GETCONF``/``GSMIOC_SETCONF`` ioctl.

-2.4 obtain base gsmtty number for the used serial port::
+#. Obtain base gsmtty number for the used serial port::

- #include <stdio.h>
- #include <stdint.h>
- #include <linux/gsmmux.h>
- #include <linux/tty.h>
- #define DEFAULT_SPEED B115200
- #define SERIAL_PORT /dev/ttyS0
+ #include <stdio.h>
+ #include <stdint.h>
+ #include <linux/gsmmux.h>
+ #include <linux/tty.h>
+ #define DEFAULT_SPEED B115200
+ #define SERIAL_PORT /dev/ttyS0

int ldisc = N_GSM0710;
struct gsm_config c;
--
2.35.1