Subject: Re: is TIOCMGET supposed to reflect reality?
To: Tom Yu <>
From: David Laight <>
List: tech-kern
Date: 09/27/2004 07:36:40
> Is there any reason not to always enable DCD and CTS interrupts?  I
> gather that there might be performance reasons for disabling DCD and
> CTS interrupts, but if the interrupts are disabled, TIOCMGET would
> have to explicitly read RR0 to get the correct state of the modem
> status lines.

If either of them are disconnected at the far end of a serial cable
then, because of cross-talk between the and because the cable acts as
an antenna, you get lots (and I means lots) of transitions on the
modem signallines.
Even if you need these interrupts, the code should poll the signal
for one of the transitions in order to do software debounce.

David Laight: