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From: janhen@sci.kun.nl (Jan Hendrikx)
Newsgroups: comp.sys.amiga.tech
Subject: Re: "Device" vs. "Handler"??
Message-ID: <2117@wn1.sci.kun.nl>
Date: 24 Aug 90 15:38:15 GMT
References: <082090.120745@ckctpa.UUCP> <25339.26d3ba57@kuhub.cc.ukans.edu>
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In article <25339.26d3ba57@kuhub.cc.ukans.edu> markv@kuhub.cc.ukans.edu writes:
>Finally the example of MSH: is BOTH a device and a handler.  The MSH:
>part is a handler that provides a AmigaDOS interface to a MS-DOS file
>system.  In practice this would be all that is needed.  MSH also
>provides a device driver to access the floppy hardware because of bugs
>in trackdisk.device, so messydisk.device is a device.

And because the IBM disk format is different from the Amiga's. The
messydisk.device CMD_READ and CMD_WRITE (et al) commands encode the
data the user (or usually, the file system handler (MSH:)) wants to
read or write different from the way the trackdisk.device does. So the
messydisk.device is used as a kind of front-end for the
trackdisk.device: it accepts all the same commands that trackdisk does,
and actually performs some of them itself, while it delegates others to
trackdisk. This way, a maximum hardware compatibility is maintained.
(Actually, it does some fiddling with the hardware itself, but only
because the 1.3 trackdisk.device does not allow some operations that I
really need. I expect the 2.0 trackdisk.device has been improved in
this respect.)

>Mark Gooderum			Only...		\    Good Cheer !!!

-Olaf Seibert.