Re: [PATCH] barrier patch set

[Johannes Stezenbach <js@convergence.de>]

Bartlomiej Zolnierkiewicz wrote:
> On Saturday 20 of March 2004 00:01, Matthias Andree wrote:
> >
> > BTW, speaking of identify-device, hdparm -i (which uses
> > HDIO_GET_IDENTITY) always returns "WriteCache=enabled" while hdparm -I
> > that uses HDIO_DRIVE_CMD with WIN_PIDENTIFY reports the "correct" state
> > that I've previously set with -W0. This is an i386 machine w/ 2.6.5-rc1.
> >
> > Is HDIO_GET_IDENTITY working correctly?
> 
> There were reports that on some drives you can't disable write cache
> and even (?) that some drives lie (WC still enabled but marked as disabled).

hdparm -i and -I ultimately both interpret WIN_IDENTIFY result, and both test
bit 0x0020 of word 85. So it's unclear to me why they report a
different write cache setting. I added a hexdump to dump_identity()
in hdparm.c, and found that bit 0x0020 of word 85 is always set.

BTW, 'cat /proc/ide/hda/identify' or 'hdparm -Istdin </dev/ide/hda/identify'
reports the same value as hdparm -I, and that is consistent with
the value I set with hdparm -W x.


So, is HDIO_GET_IDENTITY broken?

Johannes