在 Linux 中处理 /dev/tty 设备上的用户中断（UART 中断）

Posted 2023-02-22

【中文标题】在 Linux 中处理 /dev/tty 设备上的用户中断（UART 中断）

【英文标题】：Handling User-Break (UART Break) on a /dev/tty device in Linux

【发布时间】：2009-06-10 21:29:17

【问题描述】：

这里是一些代码示例，但问题是当使用“putty”通过串行线路发送“break”时，信号处理程序不被调用。

#include <sys/ioctl.h>
#include <termios.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/signal.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>

void signal_handler(int status);

int main(void)

    FILE* f = fopen("/dev/ttyS0", "r+b");

    struct sigaction saio; /* definition of signal action */
    saio.sa_handler = signal_handler;
    // saio.sa_mask = 0;
    saio.sa_flags = 0;
    saio.sa_restorer = NULL;
    sigaction(SIGINT,&saio,NULL);

    struct termios options;

    tcgetattr (fileno(f), &options);

    cfsetispeed(&options, B9600);
    cfsetospeed(&options, B9600);

    options.c_iflag &= ~IGNBRK; // & ~IGNPAR;
    options.c_iflag |= BRKINT; // | PARMRK | INPCK;
    options.c_cc[VMIN] = 0;
    options.c_cc[VTIME] = 1;

    if (tcsetattr(fileno(f), TCSAFLUSH, &options) == -1)
    
        printf("port setup failure\n");
        return -1;
    

    ioctl(fileno(f), TIOCSCTTY, (char *)NULL);
    while (1) 
        int ch = fgetc(f);
        switch (ch) 
        case EOF: break;
        case EAGAIN: printf("[EAGAIN]"); break;
        case EBADF: printf("[EBADF]"); break;
        case EINTR: printf("[EINTR]"); break;
        case EIO: printf("[EIO]"); break;
        case EOVERFLOW: printf("[EOVERFLOW]"); break;
        default:
            if (isprint(ch))
                putchar(ch);
            else
                printf("[%02x]", ch);
        
    


void signal_handler(int status)

    printf("received SIGINT %d signal.\n", status);
    exit(0);

这是我的 stty 设置：

user@dev:~/$ sudo stty -F /dev/ttyS0
speed 9600 baud; line = 0;
intr = <undef>; quit = <undef>; erase = <undef>; kill = <undef>; eof = <undef>; start = <undef>; stop = <undef>; susp = <undef>; rprnt = <undef>; werase = <undef>;
lnext = <undef>; flush = <undef>; min = 0; time = 1;
-imaxbel
-opost -onlcr
-icanon -iexten -echo -echoe -echok -echoctl -echoke

我错过了什么/为什么我没有收到信号？我正在使用 USB-2-Serial 转换器，我可以看到中断已发送过来，但在此客户端上根本没有触发任何内容。

【参考方案1】：

在strace 监督下试一试。在您的 tcsetattr 之后添加对 tcgetattr 的呼叫，并检查您要求的所有更改是否已完成 在获得新的 tty 之前，您还应该摆脱您的控制 tty。根据 man tty-ioctl ：

   Controlling tty
       TIOCSCTTY int arg
              Make  the given tty the controlling tty of the calling process.  The calling process must be a session leader and not have a controlling tty already.  If
              this tty is already the controlling tty of a different session group then the ioctl fails with EPERM, unless the caller is root  and  arg  equals  1,  in
              which case the tty is stolen, and all processes that had it as controlling tty lose it.

       TIOCNOTTY void
              If  the  given tty was the controlling tty of the calling process, give up this controlling tty.  If the process was session leader, then send SIGHUP and
              SIGCONT to the foreground process group and all processes in the current session lose their controlling tty.