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usb-storage: automatically recognize bad residues

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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>
This commit is contained in:
Alan Stern 2008-07-29 11:58:06 -04:00 committed by Greg Kroah-Hartman
parent 1a21175a61
commit 59f4ff2ecf
1 changed files with 15 additions and 2 deletions
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17
drivers/usb/storage/transport.c
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@ -1032,8 +1032,21 @@ int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us)
/* 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));