Subject: Re: Serial Line Weirdness/Bug?
To: None <email@example.com>
From: Greg A. Woods <firstname.lastname@example.org>
Date: 07/13/2000 16:58:46
[ On Thursday, July 13, 2000 at 09:24:00 (-0700), Jason R Thorpe wrote: ]
> Subject: Re: Serial Line Weirdness/Bug?
> On Fri, Jul 14, 2000 at 12:01:16AM +1000, Robert Elz wrote:
> > The right way to fix this is to change the settings in /etc/ttys
> > (mark tty00 with the "local" flag) and then run ttyflags -a
> > which will make the driver ignore carrier until you explicitly
> > change it back again.
> Actually, the *right* way is to use the dialout device, /dev/dty00 :-)
Ah ha! Since the documentation doesn't seem to have been updated yet (I
looked in tty(4), com(4) & other driver pages, and of course termios(4))
I wonder if these mystical dialout devices also have the added benefit
of still generating a SIGHUP when DCD disappears after they're open
(i.e. unless the CLOCAL flag has been explicitly set of course)....
> Now that we have dialout devices, the sticky flags set by ttyflags(1)
> are no longer really necessary.
Mabye TIOCFLAG_CLOCAL isn't 100% necessary but the rest sure are!
I still think I do need to supply a fix to ttyflags(8) that allows an
appropriately privilged user to bypass having to edit /etc/ttys and just
set the flags specified in a command-line option.... Sometimes a little
extra rope can go a long way! ;-)
(Note that TIOCFLAG_SOFTCAR isn't very well documented either --
i.e. ttys(5) says only that the very badly named "softcar" is used to
``ignore hardware carrier'' when in truth it simply turns on the default
CLOCAL flag and also turns off the default HUPCL flag.)
(I also see that there are some subtle differences between various
drivers, such as dev/ic/com.c and dev/ic/z8530tty.c in how DTR is
treated at boot time.)
Greg A. Woods
+1 416 218-0098 VE3TCP <email@example.com> <robohack!woods>
Planix, Inc. <firstname.lastname@example.org>; Secrets of the Weird <email@example.com>