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    SubjectRe: [Bisected] [Bug #13821] Replugging USB serial converter uses new device node
    Date
    Alan Stern <stern@rowland.harvard.edu> writes:

    > On Mon, 27 Jul 2009, Carlos R. Mafra wrote:
    >
    >> On Sun 26.Jul'09 at 22:28:27 +0200, Rafael J. Wysocki wrote:
    >>> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=13821
    >>> Subject : Replugging USB serial converter uses new device node
    >>> Submitter : Ferenc Wagner <wferi@niif.hu>
    >>> Date : 2009-07-18 20:04 (9 days old)
    >>> References : http://marc.info/?l=linux-kernel&m=124794754015776&w=4
    >>
    >> I was scanning the regressions list and noticed that I could reproduce
    >> this bug.
    >>
    >> So I bisected it to commit 335f8514f200e63d689113d29cb7253a5c282967
    >> ("tty: Bring the usb tty port structure into more use"), from Alan
    >> Cox.
    >>
    >> I did not double check if reverting it from -rc4 fixes the issue,
    >> but I noticed that this patch touches drivers/usb/serial/option.c, which
    >> is the driver I used to test this problem.
    >>
    >> If there is anything else I can do (give more info, test patches etc),
    >> please let me know.
    >
    > Are you certain this really is a regression? Under 2.6.30 and 2.6.27
    > the same thing happened if I unplugged a USB serial device while it was
    > in use.

    My original report is about unplugging the USB servial device *after*
    using it.

    > Can you check whether the device is still being used when you unplug
    > it? For instance, is there still a pppd process trying to communicate
    > with the device?

    I checked and rechecked that the pppd process is already dead by the
    time I unplug the device. However, the minor number did not increase
    if I unplugged the device without using it beforehand, as expected.

    > In short, it seems likely that this is not new behavior but rather the
    > way usb-serial has worked all along.

    I didn't experience this problem with 2.6.30: my ppp script was
    hardwired to use ttyUSB0 and it always worked. Now with 2.6.31-rc3 it
    does not, as the device node keeps changing.

    I'll test this with opening ttyUSB directly from the shell, instead of
    via pppd, and report back whether it makes a difference.
    --
    Regards,
    Feri.


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