From: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Linux IDE <linux-ide@vger.kernel.org>, Jens Axboe <axboe@suse.de>
Subject: Re: libata vs ATAPI
Date: Wed, 13 Oct 2004 01:03:58 +0200 [thread overview]
Message-ID: <58cb370e04101216036013d3fe@mail.gmail.com> (raw)
In-Reply-To: <416C5093.7050304@pobox.com>
On Tue, 12 Oct 2004 17:45:55 -0400, Jeff Garzik <jgarzik@pobox.com> wrote:
> Bartlomiej Zolnierkiewicz wrote:
> > INQUIRY is done in PIO in ide-scsi and it works for this device
>
> I wouldn't mind doing non-read/write commands with PIO. As long as the
> "fast path" commands are done via DMA...
Exactly my POV.
> >>>>>Unfortunately it doesn't help because atapi_pio_sector() assumes
> >>>>>transfer length to be % SECTOR_SIZE and transfer length for INQUIRY
> >>>>>is mere 36 bytes so this fails.
> >>>>
> >>>>Yes, you are welcome to fix this assumption. :)
> >>>
> >>>Another bug in this area: bcount is set to 64 * 1024 (0xFFFF) but
> >>>ATA/ATAPI spec defines max bcount as 0xFFFE and there must
> >>>be some reason why ide-scsi limits it to 63 * 1024 and ide-cd to
> >>>32 * 1024.
> >>
> >>bcount should be set to 8K (one SATA FIS) for PIO,
> >>and 0xFFFF for DMA. It's not used for DMA.
> >
> >
> > According to ATA/ATAPI-5 spec bcount is ignored for
> > non-PIO transfers.
>
> Right. In practice for some host controllers it should be set to
> 0xffff. It looks like I should change atapi_xlat() to do that.
>
>
> > It sets bcount also for no-data which seems wrong.
>
> well some "non-data" commands could still return sense, so I preferred
> to err on the side of caution.
>
>
> >>Where is this code in libata?
> >
> > atapi_xlat() in libata-scsi.c
>
> I do not see code in atapi_xlat() that sets bcount to 0xffff?
My mistake, it is setting bcount to 8K (SATA FIS). Sorry for noise.
> Jeff
>
>
next prev parent reply other threads:[~2004-10-12 23:03 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-12 20:21 libata vs ATAPI Bartlomiej Zolnierkiewicz
2004-10-12 20:50 ` Jeff Garzik
2004-10-12 21:17 ` Bartlomiej Zolnierkiewicz
2004-10-12 21:22 ` Jeff Garzik
2004-10-12 21:36 ` Bartlomiej Zolnierkiewicz
2004-10-12 21:45 ` Jeff Garzik
2004-10-12 23:03 ` Bartlomiej Zolnierkiewicz [this message]
2004-10-15 13:13 ` Jens Axboe
2004-10-15 17:17 ` Jeff Garzik
2004-10-12 21:30 ` Jeff Garzik
2004-10-12 21:39 ` Bartlomiej Zolnierkiewicz
2004-10-12 21:46 ` Jeff Garzik
2004-10-14 7:13 ` Jens Axboe
2004-10-14 19:19 ` Bartlomiej Zolnierkiewicz
2004-10-14 21:15 ` Bartlomiej Zolnierkiewicz
2004-10-15 5:00 ` Jeff Garzik
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