USB Storage: indistinguishable devices with broken and unbroken firmware

there's a USB mass storage device which exists in two version. One
reports the correct size and the other does not. Apart from that they
are identical and cannot be told apart. Here's a heuristic based on the
empirical finding that drives have even sizes.


Signed-off-by: Oliver Neukum <oneukum@suse.de>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index 70234f5dbeeb..e227f64d5641 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -153,6 +153,12 @@ static int slave_configure(struct scsi_device *sdev)
                 if (us->flags & US_FL_FIX_CAPACITY)
                         sdev->fix_capacity = 1;
 
+                /* A few disks have two indistinguishable version, one of
+                 * which reports the correct capacity and the other does not.
+                 * The sd driver has to guess which is the case. */
+                if (us->flags & US_FL_CAPACITY_HEURISTICS)
+                        sdev->guess_capacity = 1;
+
                 /* Some devices report a SCSI revision level above 2 but are
                  * unable to handle the REPORT LUNS command (for which
                  * support is mandatory at level 3).  Since we already have