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Date: Tue, 16 Sep 2003 15:49:55 -0400
From: Jeff Garzik <jgarzik@pobox.com>
To: Jens Axboe <axboe@suse.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       torvalds@osdl.org, Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: 2.7 block ramblings (was Re: DMA for ide-scsi?)
Message-ID: <20030916194955.GC5987@gtf.org>
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On Mon, Sep 15, 2003 at 09:34:45AM +0200, Jens Axboe wrote:
> On Sat, Sep 13 2003, Jeff Garzik wrote:
> > Oh, and I'm pondering the best way to deliver out-of-bang ATA taskfiles
> > and SCSI cdbs to a device.  (for the uninitiated, this is lower level
> > than block devices / cdrom devices / etc.)
> > 
> >  ... AF_BLOCK is not out of the question ;-)
> 
> Eh... I wont comment on that. I think we are way into Garzik lala land
> there :)
> 
> I'd prefer just keeping sg_io_hdr, but dumping sg. A fully fledged bsg
> (block sg) implementation. That way programs continue to work like
> before on ATAPI/SCSI, for ATA we can use it as a task file transport.

I don't propose dumping the ugly "submit cdb/taskfile" ioctls, but we do
need to deprecate them.  The ioctls are awful for throughput, async
queueing, and the like.  And of course in general, ioctls are evil :)

And we should deprecate them with a solution that aligns what with Linus
described in Dec 2001 on lkml:  a chrdev where userland write(2)s cdbs
and taskfiles, and read(2)s the results.  This is where my thinking
picked up:  if we are creating a chrdev to send "packets" and receive
responses to those packets............  <insert conclusion here>

	Jeff



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