linux-kernel - Re: [PATCH v2] tty: n_gsm: CR bit value should be 0 when config "initiator=0"

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Date:   Thu, 15 Jul 2021 10:29:36 +0800
From:   赵振国 <zhenguo6858@...il.com>
To:     赵振国 <zhenguo6858@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] tty: n_gsm: CR bit value should be 0 when config "initiator=0"

Dear Jiri,Greg

ngsm as responser，pls review the process again.
because according to this process, it can't work.

Thanks!

赵振国 <zhenguo6858@...il.com> 于2021年7月7日周三 下午2:12写道：
>
> Dear Jiri,Greg
>
>  1:   our development board uses linux kernel , uart dev node is "/dev/ttyGS2"
>  2:   config uart "/dev/ttyGS2" ,we use ngsm ldisc,and config
> "c.initiator = 0;" code is as follows
>
>   #include <stdio.h>
>   #include <stdint.h>
>   #include <linux/gsmmux.h>
>   #include <linux/tty.h>
>   #define DEFAULT_SPEED      B115200
>   #define SERIAL_PORT        /dev/ttyGS2
>
>      int ldisc = N_GSM0710;
>      struct gsm_config c;
>      struct termios configuration;
>      uint32_t first;
>
>      /* open the serial port */
>      fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY | O_NDELAY);
>
>      /* configure the serial port : speed, flow control ... */
>
>      /* use n_gsm line discipline */
>      ioctl(fd, TIOCSETD, &ldisc);
>
>      /* get n_gsm configuration */
>      ioctl(fd, GSMIOC_GETCONF, &c);
>      /* we are responter and need encoding 0 (basic) */
>      c.initiator = 0;
>      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();
>
> 3:  connect to ubuntu by uart serial port cable,ubuntu uart dev node
> is /"dev/ttyUSB0"
> send  DLC0 SABM command by "/dev/ttyUSB0",but linux development board
> can't response,code is as follows
>
> int main(int argc, char **argv)
> {
>     int fd;
> fd = open("/dev/ttyUSB0,O_RDWR | O_NOCTTY | O_NDELAY);
> char buf[256]={0xf9,0x03,0x3f,0x01,0x1c,0xf9};
> write(fd,buf,6);
> close(fd);
> }
>
> 4:  linux development board receive data,by uart,gsm_queue will check
> CR,find CR=1.so go to invalid,pls check again.
> static void gsm_queue(struct gsm_mux *gsm)
> {
> cr ^= 1 - gsm->initiator; /* Flip so 1 always means command */
> dlci = gsm->dlci[address];
>
> switch (gsm->control) {
> case SABM|PF:
> if (cr == 0)
> goto invalid;
> if (dlci == NULL)
> dlci = gsm_dlci_alloc(gsm, address);
> if (dlci == NULL)
> return;
> if (dlci->dead)
> gsm_response(gsm, address, DM);
> else {
> gsm_response(gsm, address, UA);
> gsm_dlci_open(dlci);
> }
> break;