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Subject: Re: swsusp: don't eat ide disks
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Jens Axboe <axboe@suse.de>
Cc: Linus Torvalds <torvalds@transmeta.com>, Pavel Machek <pavel@ucw.cz>,
       benh@kernel.crashing.org,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Mon, 2002-11-04 at 09:44, Jens Axboe wrote:
> It's probably not a good idea to rely on ata drives that also speak
> atapi, to my knowledge only a few old WDC drives ever did that. Since we
> are basically moving to the point where "SCSI" commands is the
> commandset that the block layer uses to make drivers do things for it,
> I had the idea of doing a rq -> taskfile conversion for ide. Just for
> simple things like read/write and sync cache, basically stuff that is
> directly translatable. That would make Linus' example actually work, and
> it would also make the direct read/write programs using SG_IO work on
> IDE drives as well.

Going beyond IDE it might be cleaner to be able to do

	struct bio_command_ops
	{
		eject: idedisk_eject,
		suspend: idedisk_suspend,
		identify: idedisk_identify,
		...
		[maybe even read:/write: in some cases
		 like smart scsi raids]
	}

that way IDE disk and all the other weirdass drives can have -one-
command parser not the twenty differently buggy ones we have now simply
by doing


	if(rq_is_command(rq))
		bio_do_command(rq, &bio_command_ops);

Its also very convenient as we can add fields to the structure and then
to drives without breaking the API and without so much updating

Alan

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