ot memory allocation question

[Brian Buhrow]

	Hello.  A tty line discipline is a layer of code above the serial
driver that implements most of the common functions that all serial ports
support.  I'm more familiar with tty line disciplines in BSD than Linux,
but the tty line discipline, for example, is what allows you to log into a
terminal via ssh or telnet and use the same terminal based programs that
you do when you log in via a hard serial line.  It provides the terminal
processing you get when you press control characters, set line length and
row count parameters and the like.  A line discipline can be as complex as
the tty discipline, which is very sophisticated and has many features grown
over many years, or it can be a simple layer that simply passes buffers of
data up and down the tty stack to allow you to talk to the serial ports.
Examples of line disciplines are: the tty discipline already mentioned,
PPP, Tablet, SLIP and one for the old Metricom Metro radios called Strip
(Star Mode IP).  My guess is the easiest way to fix the serial port problem
is to write a simple tty discipline which mostly calls the internal
functions of the tty line discipline code so as to allow Speakup to
manipulate the underlying serial port in a way that it expects regardless
of the underlying serial port type, i.e. whether it's USB, a hard serial
line or a pseudo terminal that pumps characters over the net to a remote
speech synthesizer.

Hope that helps.
-Brian

On Jul 19, 11:26am, covici at ccs.covici.com wrote:
} Subject: Re: ot memory allocation question
} What  is a tty line discipline?  Lets figure this out and do it -- ask
} the kernel people for some documentation if necessary.
} 
} Chris Brannon <chris at the-brannons.com> wrote:
} 
} > covici at ccs.covici.com writes:
} > 
} > > So could we use this inspeakup to write and read from a serial device --
} > > thus circumventing most of our serial problems?
} > 
} > No.  We discussed this several years ago, and we concluded that it won't
} > work.  It's pretty much infeasible to use the tty devices (/dev/ttyS*)
} > from kernel space.  That discussion might be available in the list
} > archives.  I've been told that the solution to our serial problems in
} > Speakup is to write a tty line discipline.  I don't really understand
} > how to do it.
} > 
} > -- Chris
} > _______________________________________________
} > Speakup mailing list
} > Speakup at linux-speakup.org
} > http://linux-speakup.org/cgi-bin/mailman/listinfo/speakup
} 
} -- 
} Your life is like a penny.  You're going to lose it.  The question is:
} How do
} you spend it?
} 
}          John Covici
}          covici at ccs.covici.com
} _______________________________________________
} Speakup mailing list
} Speakup at linux-speakup.org
} http://linux-speakup.org/cgi-bin/mailman/listinfo/speakup
>-- End of excerpt from covici at ccs.covici.com