Path: utzoo!utgpu!cunews!bnrgate!brtph3!brchh104!brchs1!bnr.ca!rice.edu!sun-spots-request
From: paul@altar.ee.byu.edu (Paul Rawlins)
Newsgroups: comp.sys.sun
Subject: Character Device Driver
Keywords: Miscellaneous
Message-ID: <1318@brchh104.bnr.ca>
Date: 16 Jan 91 23:44:12 GMT
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I have a board on the VMEBus which needs to be able to transfer packets
ranging from 1 - 100,000 bytes quickly.  I have a "driver" which uses
mmap() that works fairly well.  However, I need a real driver (primarily
for interrupt capability) which works at roughly the same rate.  I have
written one using the physio() routine as described in Sun's "Writing
Device Drivers" manual.  The problem is that for repeated short transfers,
the driver gets clobbered by the overhead in calling the write, physio,
and strategy routines.  

Does anyone know of references or example programs (preferably via ftp)
which describe character drivers in more detail?  Any help would be
greatly appreciated.

Paul Rawlins
paul@ee.byu.edu