From: Alan Stern <stern@rowland.harvard.edu>
To: "Roberts-Thomson, James" <James.Roberts-Thomson@NBNZ.CO.NZ>
Cc: Stefano Rivoir <s.rivoir@gts.it>,
Kernel development list <linux-kernel@vger.kernel.org>,
USB development list <linux-usb-devel@lists.sourceforge.net>
Subject: RE: [linux-usb-devel] Kernel unable to read partition table on US B Memory Key
Date: Wed, 6 Jul 2005 10:30:09 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.0507061021500.5278-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <40BC5D4C2DD333449FBDE8AE961E0C334F9369@psexc03.nbnz.co.nz>
On Wed, 6 Jul 2005, Roberts-Thomson, James wrote:
> Alan,
>
> > Try putting delays at various spots in sd_revalidate_disk:
> > the beginning, the middle, and the end.
>
> OK, the attached patch works for me when sd_mod was loaded with delay_use=1.
>
> Now I'm quite prepared to be told that this is a really horrible and
> inapproprate hack (given that I am not a kernel developer, I don't really
> know the "correct" way to solve this problem); and I'll cheerfully admit
> that it doesn't really solve the problem cleanly as can be seen below:
It would have been better simply to call msleep, but never mind.
> Jul 6 14:44:52 pc196344 kernel: sd: waiting for device to get ready.
> Jul 6 14:44:53 pc196344 kernel: sda: Unit Not Ready, sense:
> Jul 6 14:44:53 pc196344 kernel: : Current: sense key: Unit Attention
> Jul 6 14:44:53 pc196344 kernel: Additional sense: Not ready to ready
> change, medium may have changed
> Jul 6 14:44:53 pc196344 kernel: sda : READ CAPACITY failed.
> Jul 6 14:44:53 pc196344 kernel: sda : status=1, message=00, host=0,
> driver=08
> Jul 6 14:44:53 pc196344 kernel: sd: Current: sense key: Unit Attention
> Jul 6 14:44:53 pc196344 kernel: Additional sense: Not ready to ready
> change, medium may have changed
> Jul 6 14:44:53 pc196344 kernel: sda: test WP failed, assume Write Enabled
> Jul 6 14:44:53 pc196344 kernel: sda: assuming drive cache: write through
> Jul 6 14:44:53 pc196344 kernel: sd: waiting for device to get ready.
> Jul 6 14:44:54 pc196344 kernel: sda: Unit Not Ready, sense:
> Jul 6 14:44:54 pc196344 kernel: : Current: sense key: Unit Attention
> Jul 6 14:44:54 pc196344 kernel: Additional sense: Not ready to ready
> change, medium may have changed
> Jul 6 14:44:54 pc196344 kernel: sda : READ CAPACITY failed.
> Jul 6 14:44:54 pc196344 kernel: sda : status=1, message=00, host=0,
> driver=08
> Jul 6 14:44:54 pc196344 kernel: sd: Current: sense key: Unit Attention
> Jul 6 14:44:54 pc196344 kernel: Additional sense: Not ready to ready
> change, medium may have changed
> Jul 6 14:44:54 pc196344 kernel: sda: test WP failed, assume Write Enabled
> Jul 6 14:44:54 pc196344 kernel: sda: assuming drive cache: write through
> Jul 6 14:44:54 pc196344 kernel: sd: waiting for device to get ready.
> Jul 6 14:44:55 pc196344 kernel: SCSI device sda: 255488 512-byte hdwr
> sectors (131 MB)
> Jul 6 14:44:55 pc196344 kernel: sda: Write Protect is off
> Jul 6 14:44:55 pc196344 kernel: sda: Mode Sense: 03 00 00 00
> Jul 6 14:44:55 pc196344 kernel: sda: assuming drive cache: write through
> Jul 6 14:44:55 pc196344 kernel: /dev/scsi/host5/bus0/target0/lun0: p1
> Jul 6 14:44:55 pc196344 kernel: Attached scsi removable disk sda at scsi5,
> channel 0, id 0, lun 0
>
> There are three delays from my patch in the above list,
Yes. Why are there three instead of just one? The sd_revalidate_disk
routine should only be called once (although a bug in recent kernels
causes it to be called twice).
> and increasing the
> delay to 3 seconds didn't help, as I got three one-second delays.
I don't understand. Why didn't you get three three-second delays?
> However, if someone with the appropriate knowledge could transform my kludge
> into a proper fix, then I would be very happy.
Can you try adding delays before, after, and inbetween the calls to
sd_read_capacity, sd_read_write_protect_flag, and sd_read_cache_type, all
near the end of sd_revalidate_disk?
> Alan, thanks very much for your help - I really appreciate the quick
> responses you have given me.
>
> Note that I now have the output from the USB Snoop tool under Windows if
> anyone wants it - please ask if needed to help solve the issue "correctly".
Can you make it available on a web or ftp site and post the URL for
interested parties?
Alan Stern
next prev parent reply other threads:[~2005-07-06 19:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-06 2:48 [linux-usb-devel] Kernel unable to read partition table on US B Memory Key Roberts-Thomson, James
2005-07-06 14:30 ` Alan Stern [this message]
-- strict thread matches above, loose matches on Subject: below --
2005-07-11 23:32 Roberts-Thomson, James
2005-07-11 3:45 Roberts-Thomson, James
2005-07-11 19:27 ` Alan Stern
2005-07-11 0:07 Roberts-Thomson, James
2005-07-05 21:19 Roberts-Thomson, James
2005-07-05 22:08 ` Alan Stern
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