linux-kernel - Re: [PATCH] ata: Add support for Long Logical Sectors and Long Physical Sectors

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Message-ID: <20080806160618.40058068@lxorguk.ukuu.org.uk>
Date:	Wed, 6 Aug 2008 16:06:18 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Matthew Wilcox <matthew@....cx>
Cc:	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	jgarzik@...ox.com, Matt_Domsch@...l.com,
	Matthew Wilcox <willy@...ux.intel.com>
Subject: Re: [PATCH] ata: Add support for Long Logical Sectors and Long
 Physical Sectors

> > 	-	FIFO managed for the odd command thats a funny size
> 
> ... but it's not the odd command, it's going to be the vast majority of
> them.

Put a 512 byte and a 2K sector sized disk on the same channel and its
probably nearer 50/50.

> 
> > 	-	Various other levels of software managed controller
> > 		thumping
> > 
> > It's not a passive thing and we'd want to do it post identify on the
> > drive pair as it'll often need per channel decisions (eg on FIFO)
> 
> Why can't you just disable the (controller) FIFO whenever any drive
> reports != 512 byte sectors?

Because I'd like to do better than that - and FIFO is only one of the
cases. I think your proposal basically works - providing you identify
both drives before worrying about sector sizes. Most of our other logic
is done that way - the drives are all identified then the controller makes
decisions.

The setup time method then either vetos the disk or accepts it
The existing mode_filter can be used to implement stuff like "PIO only no
DMA" cases
And if we can do it but have problems the qc_issue or device select
methods can be hooked to do the work.

Alan
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