Re: hdregs.h puts csfo at word 129 - wrong, that's vendor specific

[Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>]

On Fri, 25 Mar 2005 20:48:21 -0500, Brett Russ <russb@emc.com> wrote:
> Jeff Garzik wrote:
> > Chris Hann wrote:
> >> ide-disk.c checks csfo bit 0 to see if the cache is available on a device
> >> hdregs.h maps csfo to word 129 of the Identify Device information
> >> the latest ATA documentation, e00159r3 Mandatory IDENTIFY DEVICE
> >> information, says words 129-159 are Vendor specific.
> >>
> >> Why is the driver switching on cache operations based on a word that
> >> has nothing to do with cache?
> >
> >
> > Good question...  I would guess that it's some pre-ATA4 legacy magic,
> > but that's just a guess.
> 
> I just checked the specs for ATA[134567] (didn't have 2) and all of them
> show word 129 as vendor specific, as Chris found.
> 
> The code that's in libata-dev shows in idedisk_setup():
> 
>          /* write cache enabled? */
>          if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
>                  drive->wcache = 1;
> 
> Bart, what's the point of the csfo bit check?  If it's specific to one
> non-ATA compliant device shouldn't it be testing something else along
> with that bit?

AFAIR it was Alan who added this code, so lets ask him :)

Alan?