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From: Jeffrey Walton <noloader@gmail.com>
To: kernelnewbies <kernelnewbies@kernelnewbies.org>
Subject: How to make /dev/ttyACM0 (and friends) exclusive?
Date: Fri, 1 Mar 2019 23:29:53 -0500	[thread overview]
Message-ID: <CAH8yC8kY5Dnxpxwy-CoRcAT-spuAz+eQ7haKY1ACR02tKqy7_w@mail.gmail.com> (raw)

Hi Everyone,

I'm trying to trackdown a problem using my dialup modem. I have a
program that opens the modem and watches caller id's. It flashes the
hook when a telemarketer calls. It works well until...

When another program opens the modem then my program starts reading
intermittent responses intended for the other program.

I cannot seem to open the device in exclusive mode. The current open
is (I also tried with O_EXCL):

    int modem = open(device_path, O_RDWR | O_NOCTTY | O_SYNC);

I'm not sure if it because udev configures the device incorrectly or
the kernel driver is configured incorrectly. Or maybe it is impossible
to do.

Does anyone know how I can make the device exclusive?

Thanks in advance.

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             reply	other threads:[~2019-03-02  4:31 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-02  4:29 Jeffrey Walton [this message]
2019-03-02  7:50 ` How to make /dev/ttyACM0 (and friends) exclusive? Greg KH
2019-03-02 18:45 ` valdis.kletnieks
2019-03-02 19:36   ` Jeffrey Walton
2019-03-03  5:55     ` valdis.kletnieks
2019-03-03  8:55       ` Jeffrey Walton
2019-03-03 11:00         ` Greg KH
2019-03-04 13:04           ` Jeffrey Walton
2019-03-04 13:20             ` Greg KH
2019-03-04 15:38             ` Yann Droneaud
2019-03-04 22:01               ` valdis.kletnieks
2020-10-06 20:41                 ` Daniel Santos
2020-10-11 14:52                   ` linux lover

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