From mboxrd@z Thu Jan  1 00:00:00 1970
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Subject: Re: [DO NOT APPLY] sd take advantage of rotation speed
Date: Wed, 25 Jun 2008 12:43:50 -0500
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To: Matthew Wilcox <matthew@wil.cx>
Cc: Jens Axboe <jens.axboe@oracle.com>, Boaz Harrosh <bharrosh@panasas.com>, Ric Wheeler <ricwheeler@gmail.com>, linux-scsi@vger.kernel.org

On Wed, 2008-06-25 at 11:34 -0600, Matthew Wilcox wrote:
> On Wed, Jun 25, 2008 at 07:26:39PM +0200, Jens Axboe wrote:
> > Uhm, but it IS "a blatant layering violation", it's doing things from
> > the wrong side up :-)
> 
> That's just "doing things from a spot Jens doesn't approve of".  A
> layering violation would be SCSI knowing how elevators work.

When it was setting particular elevators, it was a layering violation
(as I said at the time).  If it's just setting a seek cost hint, that's
acceptable.

> > I don't think udev is a particularly good idea either. My plan was to
> > introduce device profiles for the queue, but it is probably a bad idea
> > to over-engineer this. So I'll keep it simple, stick to a 'zero cost
> > seek' flag instead and allow drivers to signal that. libata/ide needs to
> > check the ID page word to detect SSD drives as well, so they need a few
> > lines of change too.
> 
> One of the other patches in this mess was the libata piece to translate
> ATA8's rotation speed to SCSI's b1 VPD page, so ide is the only
> remaining work left to do (can't it die already?)

I don't think there is any IDE work to do ... the last I heard from the
manufacturers, they were all not going to bother with PATA interfaces to
SSDs ... unless this has changed?

> > I'll just stick the block bit in the 2.6.27 pending queue and let the
> > other patches go through Jeff/James/Bart.

James