*BSD News Article 18221


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From: vrao@cse.uta.edu (Vinay Rao)
Subject: Bus data structures (mbvar) in Unix kernels??
Message-ID: <1993Jul11.000512.26343@news.uta.edu>
Sender: news@news.uta.edu (USENET News System)
Nntp-Posting-Host: cse.uta.edu
Organization: Computer Science Engineering at the University of Texas at Arlington
Date: Sun, 11 Jul 1993 00:05:12 GMT
Lines: 35

Newsgroups: comp.unix.internals,comp.sys.sun.hardware,comp.unix.bsd,
comp.unix.programmer
Subject: mbvar structures in BSD kernels
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Distribution: world
Organization: Computer Science Engineering at the University of Texas at Arlington
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Hi Netters,
	I wanted to know what is the exact purpose of  mbvar structures . Does 
the driver routines as found in the bdevsw & cdevsw structures call these ?
The Sun device driver manuals seem to say that mbvar has some elaborate data 
structures for each of the cards with 
	probe routines (used by autoconfiguration)
	go,stop routines for DMA 
	the addresses at which the cards internal chip registers 
	( control & status etc) can be accessed. 

	Does this mean that there are general stop & go kernel routines for DMA which
any drivers can call while setting up DVMA giving the device specific addresses
& memory sizes?

	It also says that if DVMA space is not adequate then the controller's mbdevice 
structures are put in await queue. I am not able to visualise how this can happen
and what are the trace of the sequence of events that start from the device
switch table that go upto the harware details of the bus structures & routines. 
Is there a bus driver which is being called ? If any of you ( especially those 
at Sun ) know about these please let me know.

Thanks in advance

Vinay Rao
(vrao@csr.uta.edu)