Hi,
[I posted this info to the bugzilla at kernel.org, and it was suggested I
post to this list.]
I have a Sumvision 5.25" USB/1394 enclosure which uses a Prolific PL-3507
USB/1394 bridge chip.
The original factory firmware dated some time in 2003 had an off-by-one bug
when connected via USB (but not 1394). The kernel has an entry for that in
drivers/usb/storage/unusual_devs.h:
UNUSUAL_DEV( 0x067b, 0x3507, 0x0001, 0x0101,
"Prolific Technology Inc.",
"ATAPI-6 Bridge Controller",
USB_SC_DEVICE, USB_PR_DEVICE, NULL,
US_FL_FIX_CAPACITY | US_FL_GO_SLOW ),
I just updated to the most recent PL-3507 firmware available from
http://www.prolific.com.tw/eng/downloads.asp?ID=44
(for my enclosure the relevant file was fw_pl3507B_d042006.zip)
With that firmware the off-by-one bug is fixed, so the kernel now incorrectly
"corrects" the block device size, reporting e.g.:
scsi 10:0:0:0: Direct-Access ST320011 A 3.21 PQ: 0 ANSI: 0
sd 10:0:0:0: Attached scsi generic sg3 type 0
sd 10:0:0:0: [sdc] Adjusting the sector count from its reported value:
39102336
sd 10:0:0:0: [sdc] 39102335 512-byte logical blocks: (20.0 GB/18.6 GiB)
Since most PL-3507 enclosures are probably user-upgradable and the most
recent
firmware doesn't have the off-by-one bug, it might be better to not include
that UNUSUAL_DEV entry. Otherwise, e.g. using dd to create an image file
of the
disk omits the last sector.
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