Line Discipline or Termios lacks ?

[Thomas Doerfler]

Hello Cedric,

rtems termios has a feature to control the hardware handshake 
lines (or, actually, only the RTS line) to signal to the 
oposite side, that the receive buffer is almost full, or that 
there is more space available. This features is available in 
some console drivers, it depends on the implementation of the 
"stopRemoteTx" and "startRemoteTx" hooks. 

If the hardware driver in use supports these calls and the 
device has the CRTSCTS flag set, then termios will control the 
hardware handshake output line RTS for you.

This has nothing to do with "line discipline". The "line 
discipline" feature allows redirecting the character stream to 
certain additional, external functions, that can do wierd 
things like decoding the incoming character stream as PPP 
packets and so on. 

If the functionality in termios for hardware handshake line 
control is not sufficent for you, you might add "private" 
functions to the "ioctl" function of your device driver, which 
might in turn do whatever you want with the hardware handshake 
lines of your devices.

wkr,
	Thomas.


> Hi
> 
> I try to implement a full driver for my serial port.
> Today that's work fine with the termios and console
> shared functions but now I try to control by hand
> my line's signal like CTS or RTS. (ex :
> Get_CTS,Get_RTS)
> But I can't find how to correctly implement this
> feature.
> 
> I read some line discipline documentation and I found
> that it's possible in rtems to implement a line
> discipline like for ppp. If your have 2 different
> hardware uart on your board you should have 2
> functions to read the CTS value but you will have
> only one line discipline (the termios_built_in).
> 
> But I understand that a line discipline should be
> a shared discipline for all port. It doesn't depend of
> the hardware UART.
> 
> So to implement driver depend read or write CTS/RTS
> DSR or other, it should be in my hardware driver
> and call be rtems_termois_ioctl.
> 
> rtems_termois_ioctl have a switch to do the
> command and if it does known, it try to call the
> line discipline_ioctl function.
> 
> So if line discipline isn't hardware depend how
> can I do ?
> 
> Should I make a Termios evolution to call some other
> command ?
> 
> Thanks a lot
> 
> 
> =====
> AUBERT Cedric
> SDEL Controle Commande
> rue Nungesser & Coli
> 44860 St Aignan de Grand Lieu
> 
> E-mail : cedric_aubert at yahoo.fr
> Http : http://www.controle-commande.sdel.fr/
> 
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