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To: Sujal Patel <smpatel@wam.umd.edu>
cc: David Dawes <dawes@rf900.physics.usyd.edu.au>,
        "Jordan K. Hubbard" <jkh@time.cdrom.com>, hackers@freebsd.org
Subject: Re: /dev/io 
In-reply-to: Your message of "Sat, 30 Dec 1995 23:18:14 EST."
             <Pine.BSF.3.91.951230231022.242A-100000@sl-046.sl.cybercomm.net> 
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Date: Sat, 30 Dec 1995 20:48:10 -0800
From: "Amancio Hasty Jr." <hasty@rah.star-gate.com>
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>>> Sujal Patel said:
 > On Sun, 31 Dec 1995, David Dawes wrote:
 > 
 > > >I think a few X servers would definitely break of /dev/io went away
 > > >suddently, but I also see no reason why the other interface couldn't
 > > >be implemented in parallel with a change-over at some point in the
 > > >future.
 > > 
 > > For what it's worth, the XFree86 servers get I/O permission by using
 > > the KDENABIO ioctl in the console driver rather than by opening /dev/io.
 > 
 > I wasn't even aware that this existed, but looking at the Xserver source
 > it seems like BSDI, Linux, FreeBSD, and NetBSD all have it (but only
 > Free/NetBSD use it for Xserver IO permission). 
 > 
 > This makes it even easier to phase out /dev/io, because the Xservers will
 > not break and the code for iopl() would be very similar to the code for
 > the KDENABIO ioctl.  The only non-trivial thing would be implementing IO
 > permission bitmaps, but I'm not even sure if it's worth it since it would
 > be a rarely used feature. 
 > 

I implemented i/o bitmap permissions way back for 386bsd you may be 
able to get the original patches if you search minnies mail archive.
Yes, I know that the patches would not apply to the current kernel
however for anyone interested it would show how it was done.

	Have fun,
	Amancio