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SubjectRE: [linux-usb-devel] Kernel unable to read partition table on US B Memory Key
Date
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:

Jul 6 14:44:50 pc196344 kernel: usb 1-6: new high speed USB device using
ehci_hcd and address 6
Jul 6 14:44:50 pc196344 kernel: Initializing USB Mass Storage driver...
Jul 6 14:44:50 pc196344 kernel: scsi5 : SCSI emulation for USB Mass Storage
devices
Jul 6 14:44:50 pc196344 kernel: usbcore: registered new driver usb-storage
Jul 6 14:44:50 pc196344 kernel: USB Mass Storage support registered.
Jul 6 14:44:50 pc196344 kernel: usb-storage: device found at 6
Jul 6 14:44:50 pc196344 kernel: usb-storage: waiting for device to settle
before scanning
Jul 6 14:44:52 pc196344 kernel: Vendor: OTi Model: Flash Disk
Rev: 2.00
Jul 6 14:44:52 pc196344 kernel: Type: Direct-Access
ANSI SCSI revision: 02
Jul 6 14:44:52 pc196344 kernel: Attached scsi generic sg1 at scsi5, channel
0, id 0, lun 0, type 0
Jul 6 14:44:52 pc196344 kernel: usb-storage: device scan complete
Jul 6 14:44:52 pc196344 scsi.agent[27245]: disk at
/devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host5/target5:0:0/5:0:0:0
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, and increasing the
delay to 3 seconds didn't help, as I got three one-second delays.

However, if someone with the appropriate knowledge could transform my kludge
into a proper fix, then I would be very happy.

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".

James Roberts-Thomson
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