long-term regression with some usb mass storage devices

[Mike Lampard <mike@mtgambier.net>]

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@rowland.harvard.edu>
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