Re: WD_QUIRK_FORCE_LBA48

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Tue, Dec 15, 2009 at 01:05:52PM +0100, Michael van Elst wrote:
> On Tue, Dec 15, 2009 at 12:13:02PM +0100, Manuel Bouyer wrote:
> 
> > Err, my version of ATA6 (T13/1410D revision 1) has the same wording
> > as ATA5. It looks like this was changed between revision 1 and
> > revision 3.
> 
> Says much about how well device will conform to such a specification.
> 
> 
> > > So the wording
> > > in ATA6 regarding "one greater than the total number" is bogus
> > > and probably not implemented correctly by some devices.
> > 
> > I don't understand why you says this is bogus. As the first adressable
> > sector is 0, the total number of adressable sectors is the last 
> > LBA28-adressable sector + 1.
> 
> See here:
> 
> > > 1) Words (61:60) shall contain the value one greater than the total
> > >    number of user-addressable sectors in 28-bit addressing and shall
> 
> 
> it says 'one greater than the number of sectors' (==count+1), and not
> 'one greater than the last sector' (==count).

Right, that's bad wordings. Other wordings in 6.2.1 and 6.2.2 contradict
this, so we can reasonably expect 61:60 do contain count and not
count+1 (OSes would have troubles using such drives anyway as they
would get the size of the device wrong).

I still think the best we can do is to use 61:60 as the LBA48
boundary.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--