From owner-cvs-sys  Wed Jan 28 04:46:09 1998
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	Wed, 28 Jan 1998 23:41:18 +1100
Date: Wed, 28 Jan 1998 23:41:18 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199801281241.XAA05795@godzilla.zeta.org.au>
To: cvs-all@FreeBSD.ORG, cvs-committers@FreeBSD.ORG, cvs-sys@FreeBSD.ORG,
        msmith@FreeBSD.ORG
Subject: Re: cvs commit: src/sys/i386/isa wfd.c
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>  Modified files:
>    sys/i386/isa         wfd.c 
>  Log:
>  Fix operation with the Iomega Zip 100 ATAPI.
>  All known versions of this drive (firmware 21.* and 23.*) will lock up
>  if presented with a read/write request of > 64 blocks.  In the presence
>  of such a unit, I/O requests of > 64 blocks are fragmented to avoid
>  this.
>  
>  Revision  Changes    Path
>  1.3       +92 -13    src/sys/i386/isa/wfd.c

You could simply reject such transfers.  The new d_maxio element in
struct bdevsw should limit clustering allow physio() to do the deblocking
for raw i/o.  Deblocking in the driver is only necessary for handling
> 32K filesystem blocks, which no one should want, especially on floppies.
It is only better if large i/o sizes are significantly more efficient.

Bruce