lkml.org 
[lkml]   [2005]   [Mar]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [ patch 4/7] drivers/serial/jsm: new serial device driver
    Date
    From
    > Who needs to know if a port is open or not?
    >
    <snipped some code>
    >
    > +static ssize_t jsm_tty_baud_show(struct class_device *class_dev, char
    *buf)

    > No, please delete these, and the other sysfs files that duplicate the
    > same info that you can get by using the standard Linux termios calls.
    > There is no need for them here.
    >
    > thanks,
    > greg k-h

    Hi Greg, Wendy, all,

    Our serial port monitoring tools need to know these things, and to
    find them out *without* opening up the serial port to do an ioctl().

    For example, lets say a customer has a modem connected to a serial port.

    If you were to open up the port with an "stty -a" to get the current
    settings and signals, you would unintentionally raise RTS and DTR.

    Now the modem sees DTR raised, and might react to it by mistake.

    Usually raising and dropping RTS/DTR quickly on a modem won't hurt
    anything,
    but its not particularly a "good" when the modem is not expecting it.

    This is why we export the various signals/stats/signals to sysfs (used
    to be proc),
    so our management tools can get the information about the serial port
    without being
    intrusive by opening up the port.

    Scott
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 14:11    [W:0.023 / U:30.196 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site