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From: ws@tools.uucp (Wolfgang Solfrank)
Newsgroups: comp.unix.internals
Subject: Re: streams/ioctls
Message-ID: <WS.91Jan3121950@karl.tools.uucp>
Date: 3 Jan 91 11:19:50 GMT
References: <25370@adm.brl.mil>
Sender: news@tools.UUCP
Organization: TooLs GmbH, Bonn, W.-Germany
Lines: 22
In-reply-to: stanonik@nprdc.navy.mil's message of 2 Jan 91 17:55:02 GMT

I don't know about V.3 (maybe ttys are implemented as traditional
character devices with line discipline?), but in V.4 there are
additional messages available that the driver/module can send to
the streams head to get data from the application or put data there.

So the scenario is:
	ioctl gets converted to message and sent downstream
	module/driver sends message upstream requesting any data
	stream head sends data to module/driver
	module/driver performs ioctl
	module/driver sends message upstream containing data
	stream head puts data into app and sends ack
	module/driver acknowledges ioctl

Of course one or the other of the data transfer messages may be skipped.
This processing also supports ioctls that contain addresses of other
data structures in their parameter. Normally the second transfer message
could be substituted by including the response data in the ioctl ack.

Hope this helps...
--
ws@tools.uucp	(Wolfgang Solfrank, TooLs GmbH)	+49-228-230088