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    SubjectRe: serial ports now asserting DTR and RTS during boot; breaks connected hardware
    On Tue, 3 Jan 2012 10:37:07 -0500
    Dave Jones <davej@redhat.com> wrote:

    > Jiri,
    > We got this report from a user who notes a change in behaviour for
    > his serial hardware over the last few kernel versions.
    >
    > https://bugzilla.redhat.com/show_bug.cgi?id=771010
    >
    > This sounds like it might be related to your DTR/RTS changes back in March 2011 maybe ?

    Looks like your userspace to me at first glance.

    ftdi_sio sets up the modem lines in set_termios. Set_termios is called
    from ftdi_open. ftdi_open is triggered by userspace.

    > > The following code in the ftdi_sio driver is one suspect but this behavior
    > > happens on 8250 UARTs also so it is systemic now,

    Likewise 8250 sets up the lines in serial8250_startup. This is called via
    uart_startup which is called via open.

    I think a necessary first step would be to test a current kernel on FC14,
    or boot a sane simple kernel and test image and see what that does so all
    the udev and system startup stuff can be eliminated. Wouldn't surprise me
    at all however if something like udev triggered poking around for UPS
    devices or 3G modems wasn't the trigger ?

    Alan


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