Re: [patch 3/4] new serial flow control
From: Samuel Thibault
Date: Sun Oct 09 2005 - 05:10:11 EST
Russell King, le Sun 09 Oct 2005 09:37:24 +0100, a écrit :
> On Sun, Oct 09, 2005 at 02:21:30AM +0200, Samuel Thibault wrote:
> > Russell King, le Sun 09 Oct 2005 01:01:53 +0100, a ?crit :
> > > > How could this look like in userspace?
> > >
> > > I think they should be termios settings - existing programs know how
> > > to handle termios to get what they want.
> > Hence a new field in the termios structure?
> > There was a discussion about this back in 2000:
> > http://marc.theaimsgroup.com/?t=96514848800003&r=1&w=2
> What I was thinking of was to use some of the spare termios cflag bits
> to select the flow control. You'd only want one flow control type at
> one time though. Eg: define two fields, each to select the signal.
> 0 - RTS
> 1 - DTR
> 0 - CTS
> 1 - DTR
> 2 - DSR
It looks fine, but it might not be sufficient for expressing that:
- some flow control use RTS to indicate that DTE is ready to send data,
- some other use it to indicate that DTE wants to send data. (and CTS is
used for acknowledgment of this),
- some other use it as a strobe for acknowledging characters, some other
use it as a strobe for acknowledging frames (announced by CTS).
> However, bear in mind that the majority of the more inteligent 8250-
> compatible UARTs with large FIFOs only do hardware flow control on
Hardward flow control is usually performed in software. Can't their
hardware implementation of hardware flow control be disabled when
control method is not usual RTS/CTS?
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