MORE 6386 UUCP WOES ...

[Dave Martindale]

In article <756 at wsccs.UUCP> terry at wsccs.UUCP (Every system needs one) writes:
>In article <16509 at onfcanim.UUCP>, dave at onfcanim.UUCP (Dave Martindale) writes:
>>
>> I don't know about system V UNIXes, but on all of the older UNIX versions
>> plus the BSD variants, the default device supported modem control - it's
>> the only sane way to handle dialins.
>
>Unfortunately this is not true.  BSD, particular on Sun systems, requires a
>kernel reconfiguration to properly handle modem control on a port.  The port
>is useless without proper modem signals unless configured back.
> [references cited]

Now wait a minute.  By "older UNIX versions", I mean V6, V7, and the 4BSD
versions as distributed by Berkeley itself.  These all support modem
control, and default to it being enabled.  Berkeley added the "flags"
word to the configuration info allowing you to tell the driver on a
per-line basis that modem control signals were to be ignored.

I do not consider SunOS to be "Berkeley UNIX".  We don't have any Suns,
but comments I've read lead me to believe that they use the same "flags"
word as Berkeley, but default to all of the bits set to disable modem
control.  This does make it easier to hook up terminals to the machine
when you don't know anything about modem control, and don't want to,
so it is perhaps justfied for machines that are seen as workstations.
(I still don't like it.)

>The nowait feature is built into the O_NDELAY open flag; using the minor device
>bit 6 or 7 for this behaviour only ocassionally would be wrong.

O_NDELAY is not supported in the UNIX versions I was talking about.
In addition, UNIX tty drivers that use a minor device bit to control
"dialout" mode often provide proper interlocking between dialin and
dialout operation of a port, in the kernel, with no modification to
user code required.

>Any installation which is using a stright 3-wire cable to their terminals is
>using a non-modem control port or they have hacked the computer end of the
>cable to force DCD and possibly CTS/RTS if it is a system V system with
>AT&T's 3B2-style drivers.

True.  People with modem control enabled on their terminal ports either
use more than 3 wires (which allows the processor to detect when the terminal
has been turned off), or jumper DTR to CXR at the computer end of the
wire.

>Please examine tty.c for the comment "partial open hack" in your UNIX source.
>The 20 or so lines on either side will be enlightening.

Not in the machines I was talking about.


	Dave Martindale