From: Brett Russ <russb@emc.com>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Chris Hann <chann94501@yahoo.com>,
linux-ide list <linux-ide@vger.kernel.org>,
Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Subject: Re: hdregs.h puts csfo at word 129 - wrong, that's vendor specific
Date: Fri, 25 Mar 2005 20:48:21 -0500 [thread overview]
Message-ID: <4244BF65.6070109@emc.com> (raw)
In-Reply-To: <42437F78.8090703@pobox.com>
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?
BR
next prev parent reply other threads:[~2005-03-26 1:48 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 [this message]
2005-03-26 2:01 ` Bartlomiej Zolnierkiewicz
2005-03-27 13:58 ` Alan Cox
2005-04-13 22:18 ` Brett Russ
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