linux-kernel - Re: [PATCH v1] 8250: add support for DTR/DSR hardware flow control

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Message-ID: <20080821185938.GG7154@redhat.com>
Date:	Thu, 21 Aug 2008 14:59:39 -0400
From:	"'Aristeu Rozanski'" <arozansk@...hat.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Tosoni <jp.tosoni@...sys.fr>,
	"'Laurent Pinchart'" <laurentp@...-semaphore.com>,
	linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] 8250: add support for DTR/DSR hardware flow control

> > > > About a RS485 ioctl: could you consider the attached files which are already
> > > > in the Linux kernel (in include/asm-cris).
> > > > They define a TIOCSERSETRS485 (ioctl.h), and the data structure (rs485.h)
> > > > with allows to specify timings. Sounds just like what we want ?
> > > 
> > > I had a deeper look at this for RS485 and the answer is "sort of". I've
> > > reworked the structure to keep it the same size irrespective of 32/64bit
> > > systems, and to make stuff flags that can be, plus add some extra u32
> > > words in case we need to (.. when we need to ;)) add stuff later.
> > > 
> > > Comments, thoughts - will this do what people in the RS485 world need ?
> > as for DTR/DSR patch, will be used the same approach?
> 
> I'm still trying to get a sensible answer on how other Unixes handle it
I did some research on that:
Solaris and AIX:
	TC{G,S}ETX for extended options and only input flow control (DTRXOFF)
SCO:
	{S,G}ETFLOW for configuring flow control, TXHARD, RXHARD for DTRDSR
FreeBSD:
	cflags has 'dtrflow' and 'dsrflow'

Having the option to set individually which pins to use for input and output
flow control and which ones should be on/off all the time seem to be a powerful
way to do it, instead of having a "CDTRDSR".

-- 
Aristeu

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