Re: artpec.c / serial_core.c hardware flow control problem

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Thu, 28 Jun 2012 17:29:27 +0200
Mikael Johansson <mikael.lars.johansson@axis.com> wrote:

> Greetings,
> 
> We have a problem with drivers/serial/artpec.c (Not yet in main tree) 
> which uses hardware supported flow control (XON/XOFF). We do cfmakeraw() 
> and tcsetattr() from userspace to set a termios struct where (c_iflag & 
> IXON) is not set. The problem is that the call to tcsetattr() is not 
> propagated down to serial_artpec_set_termios(), the reason being that 
> uart_set_termios() doesn't think that IXON is a RELEVANT_IFLAG and 
> returns prematurely instead of calling uart_change_speed --> 
> ops->set_termios().
> 
> Could this be fixed by making IXON a RELEVANT_IFLAG?:

That's actually insufficient for those cases - you can set the characters
used for things as well plus IXANY and IXOFF.

It's a stupid "optimisation" and the only reason I didn't get rid of it
before was in case it broke something else. Time for it to go.

So yeah - I'd just delete it.

If you are doing hardware XON/XOFF watch c_cc[VSTART] and c_cc[VSTOP].
Those control the symbol used for soft flow control.

Alan