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Date: Mon, 14 Nov 2011 12:07:45 +0000
From: Alan Cox <alan@linux.intel.com>
To: Darron Black <darron@griffin.net>
Cc: Wolfram Sang <w.sang@pengutronix.de>,
        Claudio Scordino <claudio@evidence.eu.com>, Greg KH <greg@kroah.com>,
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        Jesper Nilsson <Jesper.Nilsson@axis.com>,
        Mikael Starvik <mikael.starvik@axis.com>
Subject: Re: [PATCH] RS485: fix inconsistencies in the meaning of some
 variables
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> Perhaps the RTS toggle after transmit delay needs to be large, and 
> they'd rather do it in userspace than block in the driver. I also
> recall a protocol that would send a master assertion command and hold
> on to RTS afterwards. I can easily imagine needing to quickly

Appletalk does this for one. Some protocols use it for priming low cpu
power receivers. You fire a header message at the target which fits
into its serial fifo, it then responds and can sit in a tight loop
getting the following frame data.

Alan