linux-kernel - usb serial: pl2303 driver TxD "break" stays after close() bug

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Date:	Thu, 5 Feb 2015 12:56:20 +0200
From:	Jari Ruusu <jariruusu@...rs.sourceforge.net>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: usb serial: pl2303 driver TxD "break" stays after close() bug

Tested on 3.10.67 and 3.18.5 kernels with ATEN UC-232A usb-serial adapter.
No patch, sorry. To actually see the stuck "break" signal on TxD line, you
need either some sort of LED or voltmeter connected to the data transmit
line. Other RS-232 serial ports that I have access to (normal PC hardware
serial ports and FTDI usb-serial adapters) do not have this bug.


/* pl2303 TxD "break" stays after close() demo */

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

int main(int argc, char **argv)
{
    struct termios tt;
    int fd;

    if(argc < 2) {
        fprintf(stderr, "usage: %s /dev/ttyUSB0\n", argv[0]);
        exit(1);
    }
    if((fd = open(argv[1], O_RDWR | O_NOCTTY, 0)) == -1) {
        perror("serial port open failed");
        exit(1);
    }
    tcgetattr(fd, &tt);
    cfmakeraw(&tt);
    tcsetattr(fd, TCSANOW, &tt);
    if(ioctl(fd, TIOCSBRK, 0) == -1) {
        perror("set BRK failed");
        exit(1);
    }
    close(fd);
    exit(0);
}

-- 
Jari Ruusu  4096R/8132F189 12D6 4C3A DCDA 0AA4 27BD  ACDF F073 3C80 8132 F189
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