Western Digital Extern HDD 1021
matthias.rampke at googlemail.com
Tue Feb 15 09:23:37 PST 2011
I had two (separate, as far as I can tell) problems with my Western
Digital Elements Desktop USB hard disk on x86_64 2.8-RELEASE.
(a) the disk would be recognised, but not usable after a reboot, but
worked fine after either power cycling the machine (i.e. turning it
off and on again) or after re-attaching the disk. In both cases the
disk powers itself down, during a reboot it does not. I have not
cross-tested this on master, but I think I had the same problem there.
(b) when writing large amounts of data to the same disk (formatted
with HAMMER) the system would panic (see the screenshot at ). This
does NOT happen on master.
I have found (through guessing and trial&error) a fix for both
problems: adding an entry to the quirks table in
sys/dev/usbmisc/umass/umass.c - see the attached patch or the gist at
(a) is fixed by adding the NO_TEST_UNIT_READY quirk. From the
description of said flag this is plausible.
(b) is fixed through IGNORE_RESIDUE. This sounds more-or-less
plausible as well, but I do not understand why this panic did not
occur on master even without this patch (umass.c has not changed
between 2.8-RELEASE and master). I can not find where this particular
quirk is ever observed, so I am at loss here concerning the underlying
reason for this.
My guess is (from what I understand about IGNORE_RESIDUE) that this
flag causes some part of the driver stack to disregard some count from
the disk and relies solely on it's own knowledge of the state of a
transfer, thus not choking on this count being off. Has this perhaps
been made the default?
PS: Thanks swildner for the advice and patience!
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