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Date:      Sat, 30 Dec 1995 23:18:14 -0500 (EST)
From:      Sujal Patel <smpatel@wam.umd.edu>
To:        David Dawes <dawes@rf900.physics.usyd.edu.au>
Cc:        "Jordan K. Hubbard" <jkh@time.cdrom.com>, hackers@freebsd.org
Subject:   Re: /dev/io
Message-ID:  <Pine.BSF.3.91.951230231022.242A-100000@sl-046.sl.cybercomm.net>
In-Reply-To: <199512310311.OAA16531@rf900.physics.usyd.edu.au>

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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. 


Sujal




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