On Wed, 30 Jul 2008, Douglas Gilbert wrote:
> James Bottomley wrote:
> > On Wed, 2008-07-30 at 10:17 -0400, Alan Stern wrote:
> >> On Tue, 29 Jul 2008, Matthew Dharm wrote:
> >>
> >>> Actually, I'm seriously starting to think that US_FL_IGNORE_RESIDUE should
> >>> just become a sysfs parameter which defaults to the 'ignore' state...
> >> We have to be careful; there definitely are devices out there which
> >> need to use the Residue.
> >
> > This is sort of a tradeoff ... there was one complaint I saw where a
> > device turned read only without the fix idenitifed in this report.
> > Devices broken by the fix are definitely crawling out of the woodwork
> > now. Either this patch needs to be reverted or a new fix needs to be
> > applied soon (and to stable).
>
> The patches to fix this that I have tried do not apply
> cleanly to lk 2.6.26 (and break during compile if forced:
> "us->fflags" is not defined).
>
> Is there a lk 2.6.26 patch available?
Sorry about that; my patches are against the USB development tree and
I tend to forget to redo them against the vanilla kernel. Below is a
patch against 2.6.26. Or you can just edit the original patch and
change the occurrences of "fflags" to "flags".
Alan Stern
Index: 2.6.26/drivers/usb/storage/transport.c
===================================================================
--- 2.6.26.orig/drivers/usb/storage/transport.c
+++ 2.6.26/drivers/usb/storage/transport.c
@@ -1034,8 +1034,21 @@ int usb_stor_Bulk_transport(struct scsi_
/* try to compute the actual residue, based on how much data
* was really transferred and what the device tells us */
- if (residue) {
- if (!(us->flags & US_FL_IGNORE_RESIDUE)) {
+ if (residue && !(us->flags & 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->flags |= US_FL_IGNORE_RESIDUE;
+
+ } else {
residue = min(residue, transfer_length);
scsi_set_resid(srb, max(scsi_get_resid(srb),
(int) residue));
--
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