From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
To: Brett Russ <russb@emc.com>
Cc: Jeff Garzik <jgarzik@pobox.com>,
Chris Hann <chann94501@yahoo.com>,
linux-ide list <linux-ide@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: hdregs.h puts csfo at word 129 - wrong, that's vendor specific
Date: Sat, 26 Mar 2005 03:01:01 +0100 [thread overview]
Message-ID: <58cb370e050325180159d5fbb1@mail.gmail.com> (raw)
In-Reply-To: <4244BF65.6070109@emc.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?
next prev parent reply other threads:[~2005-03-26 2:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-25 1:28 hdregs.h puts csfo at word 129 - wrong, that's vendor specific Chris Hann
2005-03-25 3:03 ` Jeff Garzik
2005-03-26 1:48 ` Brett Russ
2005-03-26 2:01 ` Bartlomiej Zolnierkiewicz [this message]
2005-03-27 13:58 ` Alan Cox
2005-04-13 22:18 ` Brett Russ
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