usb-storage: automatically recognize bad residues
This patch (as1119) will help to reduce the clutter of usb-storage's
unusual_devs file by automatically detecting some devices that need
the IGNORE_RESIDUE flag. The idea is that devices should never return
a non-zero residue for an INQUIRY or a READ CAPACITY command unless
they failed to transfer all the requested data. So if one of these
commands transfers a standard amount of data but there is a positive
residue, we know that the residue is bogus and we can set the flag.
This fixes the problems reported in Bugzilla #11125.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index fcbbfdb..3523a0b 100644
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -1032,8 +1032,21 @@
/* try to compute the actual residue, based on how much data
* was really transferred and what the device tells us */
- if (residue) {
- if (!(us->fflags & US_FL_IGNORE_RESIDUE)) {
+ if (residue && !(us->fflags & US_FL_IGNORE_RESIDUE)) {
+
+ /* Heuristically detect devices that generate bogus residues
+ * by seeing what happens with INQUIRY and READ CAPACITY
+ * commands.
+ */
+ if (bcs->Status == US_BULK_STAT_OK &&
+ scsi_get_resid(srb) == 0 &&
+ ((srb->cmnd[0] == INQUIRY &&
+ transfer_length == 36) ||
+ (srb->cmnd[0] == READ_CAPACITY &&
+ transfer_length == 8))) {
+ us->fflags |= US_FL_IGNORE_RESIDUE;
+
+ } else {
residue = min(residue, transfer_length);
scsi_set_resid(srb, max(scsi_get_resid(srb),
(int) residue));