Re: belkin usb serial converter (mct_u232), break not working

From: Thomas Stewart (thomas_at_stewarts.org.uk)
Date: 10/21/04

  • Next message: Thomas Gleixner: "Re: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8" 
    Date:	Thu, 21 Oct 2004 11:06:37 +0100
To: Paul Fulghum <paulkf@microgate.com>

    On Wed, Oct 20, 2004 at 09:37:58PM -0500, Paul Fulghum wrote:
    > static int send_break(struct tty_struct *tty, int duration)
    > {
    > set_current_state(TASK_INTERRUPTIBLE);
    >
    > tty->driver->break_ctl(tty, -1);
    > if (!signal_pending(current))
    > schedule_timeout(duration);
    > tty->driver->break_ctl(tty, 0);
    > if (signal_pending(current))
    > return -EINTR;
    > return 0;
    > }
    >
    > The USB serial driver break_ctl() sends a URB which does
    > a sleep and wakeup changing the task state back to TASK_RUNNING.
    > Because of this, schedule_timeout() above gets short circuited
    > and the break condition is not maintained long enough.
    >
    > The normal serial driver break_ctl() leaves the task state
    > as TASK_INTERRUPTIBLE so you get the proper delay.
    >
    > Thomas: try the patch below and let me know the results.

    I tryed again with your patch applyed, with both minicom and porttest

    porttest.c:
    #include <sys/fcntl.h>
    #include <sys/ioctl.h>
    main(int argc, char ** argv) {
            int r, fd = open(argv[1], O_RDWR|O_NOCTTY);
            r=ioctl(fd, TCSBRKP, 20);
            printf("%d\n", r);
            close(fd);
    }

    $ time ./porttest /dev/ttyS0
    0

    real 0m2.001s
    user 0m0.000s
    sys 0m0.001s
    $ time ./porttest /dev/ttyUSB0
    0

    real 0m2.003s
    user 0m0.000s
    sys 0m0.001s

    As you can see, this time there is the correct pause. However
    it still does not send the break.

    To add the mix, I dug about and found a differnt type of USB serial
    converter, a no-brand one that uses the pl2303 module. Both minicom
    and porttest with either stock 2.6.8.1 or 2.6.8.1 with your patch
    send the break fine with this different converter.

    This makes me think it is a problem with the mct_u232 driver?

    Regards 

    -- 
Tom
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