Re: [gentoo-embedded] serial port handling question

[David Relson <relson@osagesoftware.com>]

On Thu, 14 Jan 2010 04:47:53 +0100
Peter Stuge wrote:

> Daniel Stonier wrote:
> > there's a setting in the termios options structure for rts - have
> > you tried that?
> > 
> > 'man termios' - look for CRTSCTS.
> 
> Note that this flag does not directly control RTS, but rather it
> instructs the kernel whether RTS/CTS signalling should be used for
> flow control or not.
> 
> As David noticed, there is no API for directly controlling RTS in
> Linux, it can only be done by the serial driver itself or a line
> discipline driver.
> 
> 
> //Peter

Hello Peter and Daniel,

Information greatly appreciated.  I'll digest it tomorrow when I'm more
alert.

After bashing my head against the wall (including experimentation with
CRTSCTS), I spent a while reading drivers/serial/8250.c and found that
CRTSCTS used only for enabling AFE (automatic flowcontrol enabled).
Not having adequate specs for the protocol or hardware involved,
there's some mystery as to exactly why RTS is used as it is.

For certain, it'll be interesting tomorrow to learn more of termios and
line discipline drivers (a new term for me).

Ciao,

David