long-term regression with some usb mass storage devices

From: Mike Lampard
Date: Fri Feb 20 2009 - 02:11:15 EST


Hi All,

I recently plonked a dvd into my usb-attached Pioneer DVR-107d only to find
that the current kernels no longer saw the drive as DVD capable. In fact, the
kernel no longer saw _any_ features of the drive: sr0: scsi3-mmc drive: 0x/0x
caddy. After much bisecting and even more blind luck I narrowed the problem
down to this commit:

commit bdb2b8cab4392ce41ddfbd6773a3da3334daf836
Author: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Date: Tue Jun 24 14:03:14 2008 -0400

[SCSI] erase invalid data returned by device

This patch (as1108) fixes a problem that can occur with certain USB
mass-storage devices: They return invalid data together with a residue
indicating that the data should be ignored. Rather than leave the
invalid data in a transfer buffer, where it can get misinterpreted,
the patch clears the invalid portion of the buffer.

This solves a problem (wrong write-protect setting detected) reported
by Maciej Rutecki and Peter Teoh.

Regards
Mike
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