linux-kernel - Re: [PATCH] libata: always use polling SETXFER

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Message-ID: <4656D602.3010105@garzik.org>
Date:	Fri, 25 May 2007 08:26:42 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Tejun Heo <htejun@...il.com>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>, linux-ide@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] libata: always use polling SETXFER

Tejun Heo wrote:
> So, I don't think the problem exists for SATA in the first place.  At
> least there hasn't been any report of it and doing SETXFER by polling
> can handle all the existing cases.  We can and probably should deal with
> such SATA devices when and if they come up.  How are we gonna verify the
> controller doesn't crap itself and ahci TF register monitoring HSM can
> work around the weirdo when we don't have any such device?  Even if we
> determine that we need to do HSM over intelligent SATA controller now, I
> think we still need to push polling SETXFER first to take care of the
> existing cases.

Doing SETXFER by polling only handles the cases where the driver 
actually honors ATA_TFLAG_POLLING, which is /not/ always the case.

If the new policy ensures that it continues to be OK to /not/ honor 
ATA_TFLAG_POLLING -- thus limiting SETXFER polling assumptions to older 
hardware -- that's fine, and it merely needs to be documented.

But let us not make the assumption that this bandaid fixes all cases, 
because the bandaid is not applied in all cases.

	Jeff


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