[nSLUG] USB storage hot-swap question

George N. White III gnwiii at gmail.com
Sat May 17 18:51:55 ADT 2008

On Sat, May 17, 2008 at 3:51 PM, Mike Spencer <mspencer at tallships.ca> wrote:
> I wrote:
> me> But if I umount the [USB memory] device, unplug it and plug in
> me> another device, mount refuses to mount it, reporting that it is
> me> "is not a valid block device".
> And "George N. White III" <gnwiii at gmail.com> quoth:
>> I haven't seen this (on The entry in
>> /proc/scsi/scsi disappears when the device is unplugged from the USB
>> connector.
> Oh. Well, I'm using a 2.4 kernel.  USB webcam works as advertized and USB
> memory works but doesn't hot-swap properly.

You might be able to find a patch, but why not upgrade to a current
distro.  The trick for older hardware is to stiick with a lightweight window
manager.  You should consider getting a USB 2 card and disabling
any onboard USB 1 ports.  With linux, you can't expect good support
for shoddy and/or badly documented hardware unless it is very
widely used.  The trick is to spend the money you didn't spend on
software to make sure you have decent hardware.

>> A certain well-known direct vendor is notorious for USB ports that
>> don't behave.
> This is an IBM P3. "Type 6579 GJU" if the xternal sticker is to be
> believed.

Early USB hardware was a mess so the drivers were full of
special case code for workarounds.

>> Do you see lines in /var/log/messages like:
>>   May 17 14:41:50 cerberus kernel: usb 1-5: USB disconnect, address 4
> After unmounting and removing one device, then plugging in and
> attempting to mount another, /var/log/messages has:
>    May 17 15:23:09 bogus kernel: usb.c: USB disconnect on device
>                    00:1f.2-2 address 5
>    May 17 15:23:28 bogus kernel: hub.c: new USB device 00:1f.2-2,
>                    assigned address 6
>    May 17 15:24:02 bogus kernel: sda: Unit Not Ready, sense:
>    May 17 15:24:02 bogus kernel:  sda: I/O error: dev 08:00, sector 0
> Does that tell you anything useful?
>> You might be interested in <http://www.linux-usb.org/usbtest/>....
> Yow!  That makes it look like the whole USB matter is a can or worms
> under the hood.  Browsing over it, I gather I should upgrade to a 2.6
> kernel RSN.  Well, I just bought a used Dell P4 on which I'm going to
> install Slack 12/2.6 kernel. (Or was it Dell that you called "A
> certain well-known direct vendor...notorious for USB ports that don't
> behave."?)

If you think USB looks messy, try firewire.

Look in the manuals -- does it say "only for keyboard and mouse".
Again, I'd avoid USB 1 and get a USB 2 card.

> So maybe I'll just live with this hot-plug annoyance until I have that
> up and running.

Have you looked for patches?  If you have only one USB storage
device at a time, then it make sense to just remove and reload
the module.

George N. White III <aa056 at chebucto.ns.ca>
Head of St. Margarets Bay, Nova Scotia

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