Re: Serial port arbitration (UUCP device locking protocol?)
Re: Serial port arbitration (UUCP device locking protocol?)
- Subject: Re: Serial port arbitration (UUCP device locking protocol?)
- From: Dan Bernstein <email@hidden>
- Date: Tue, 15 Feb 2005 16:22:54 +0200
Thanks again Godfrey.
Sorry to keep bugging you with this, but I'm still confused. In ioss.h
it says that if the preempt flag is true, then the device is
pre-emptible, whereas in your code, you set it to 0 (false) right
before you say "Now the port is in the preemptible - blocking state".
I also tried doing a read there, and it didn't seem to be
pre-emptible. On the other hand, when I do a read after setting the
preempt flag to 1, then read blocks until another program opens the
device, at which point it returns 0. Further read return -1 with
errno==EBUSY.
Did I get it all wrong?
-- Dan
On Mon, 14 Feb 2005 10:17:06 -0800, Godfrey van der Linden
<email@hidden> wrote:
> G'day Dan,
>
> > On Sat, 12 Feb 2005 11:47:00 -0800, Godfrey van der Linden
> > <email@hidden> wrote:
> >> // At this point you have the port exclusively and non-preemtibly
> >> // so now is a good time to program up the modem or do any other
> >> // equipment initialisation you desire.
> >
> > How do I do that? Can I just write to the dialin device or should I
> > open the dialout?
>
> At this point in the sample code the fd is an exclusive open and
> non-preemptible handle on the serial port, you can read/write to it to
> talk directly to the modem.
>
> Godfrey
>
>
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