On Tue, 28 Sep 1999, John Refling wrote:

> I have had the same problem with all recent versions of NetBSD
> and the PC I have as the console.  When the console reboots, some
> where in its hardware reset sequence, the serial ports send a
> BREAK.  I have used some old (perhaps non standard) laptops   
> which do not do the same.  
> 
> A break has nothing to do with the DTR line.  A break is formed

Yep. Break has nothing to do with DTR. :-)

> by holding the TX line inactive for a second or two.  Zero voltage
> is not inactive, so pulling the cable out of the port doesn't
> send a break.  The inactive signal is a voltage between 3-20 volts
> or so (and I can't remember if it is positive or negative).  The
> active signal is the same voltage, but opposite polarity. 

bit-0, which is what is sent in a break, is a positive voltage.

> Anyway, getting back to the point, I would like to add an option
> in the kernel which will ignore the console break.  I looked thru
> the source code a long time ago, and didn't see any good way of
> doing this except by commenting out the call to the debugger.
> 
> Any other suggestions???????????

That's about the only way. Port mac68k has a kernel config option to do
this for years.

I think a better way to do this is add a sysctl which controlls this. The
kernel config option would then just initialize the value one way or the
other. When we get a break, we look at this value. If it's 1, we break. If
0, we don't.

Take care,

Bill