Alan Stern wrote:
On Mon, 11 May 2009, Phil Endecott wrote:
From: Phil Endecott <sonygpsbug@xxxxxxxxxxxx>
Add an UNUSUAL_DEV for the Sony GPS-CS1 (054c:0298), which seems to suffer from
the READ CAPACITY off-by-one and LOCKING bugs.
Signed-off-by: Phil Endecott <sonygpsbug@xxxxxxxxxxxx>
---
This device used to work for me without any fixes. It now doesn't work even with
older kernels. I don't know why; my best guess is that perhaps it didn't need
to look at the last sector until recently, maybe due to filesystem layout or
something. Because of my uncertainly I've made this a "guess capacity", not
"fix capacity".
It would be nice to see some usbmon traces showing how the device fails
when you leave out individual flags from the patch. We might be able
to tell exactly which flags are needed.
Hi Alan,
I debugged this from the "bottom up" with a USB analyser and wrote down
the SCSI commands as I deciphered them. Basically I see a READ
CAPACITY early on that returns 0000FFF0; a bit later I see reads:
Address Length
0 1
1 1F
FF00 8
FFE0 8
FFF0 1
This last one fails. (Oddly the response to REQUEST SENSE looks like
an OK to me - though I don't really know anything about SCSI error
reporting. It has 0x70 in the response code field and everything else
is 0. Did I also see a quirk related to error reporting?)
It goes on to do lots of other reads but it re-visits this
beyond-the-end sector several times and each time the read fails.
So I'm pretty certain that it is, currently, suffering from this
off-by-one bug. But I'm equally sure that it was working before, with
the same kernel. It seems unlikely that this is the sort of bug that
would come-and-go, so my guess is that it causes a problem now because
the flash is nearly full and whatever bit of filesystem metadata is
stored at the end of the device is now reaching into the last block, or
something like that.
I can also see the "prevent/allow removal" commands failing in the USB
analyser trace. That quirk is not necessary to make the device work
but it certainly makes the logs a lot quieter.
Cheers, Phil.
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