Re: [PATCH] libata: always use polling SETXFER

[Jeff Garzik <jeff@garzik.org>]

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