[MiNT] Serial port control signals in mint

[Mario Becroft <mb@tos.pl.net>]

Hello people,

While trying to make mgetty work properly under MiNT I seem to be always
running into problems with the serial ports and the control signals like
DCD and DTR.

It seems like it's not possible to read the status of serial port control
lines with ioctl. In the mintlib there seems to be kludge for this which
only works on the original ST serial port and is no use for anything else.

Also I'm not sure how this usually operates but I think it should happen
that if a user drops the carrier their shell should get a SIGHUP signal to
tell it to exit, but this doesn't seem to work properly either. I'm not
sure if this is to do with mgetty or not, I am still looking into that.
But maybe someone who knows could save me a lot of bother by explaining
how this should operate.

There is also a problem that in some circumstances (which I have not been
able to precisely discern) setting the baud rate of the serial port to 0,
which should drop DTR, has no effect and the port appears to be set to 110
baud (in other words it's not possible to set the port to 0 baud, it just
goes to 110). But other times the same port can be set to 0 baud. I can't
figure out what determines whether it will work or fail. On my TT, where
the only ports I have tested are modem1 and modem2, the problem only ever
appears on modem2; setting modem1 to 0 baud always works.

I realise that the above is somewhat vague, but I am hoping that someone
might be familiar with this and the above will be sufficient explanation.
Otherwise I will continue trying to figure it out and maybe post another
message when things are clearer.

Thank you for any suggestions.

-- 
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| Mario Becroft                * Tariland, New Zealand Atari User Group |
| mb@tos.pl.net                * Atari Hardware Developments            |
| http://www.ak.planet.gen.nz/~mario/ * Atari Serial Mouse Interface    |
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