| From stern@rowland.harvard.edu Mon Aug 18 10:39:06 2008 |
| From: Alan Stern <stern@rowland.harvard.edu> |
| Date: Tue, 5 Aug 2008 10:46:23 -0400 (EDT) |
| Subject: usb-storage: automatically recognize bad residues |
| To: stable@kernel.org |
| Message-ID: <Pine.LNX.4.44L0.0808051042120.2518-100000@iolanthe.rowland.org> |
| |
| From: Alan Stern <stern@rowland.harvard.edu> |
| |
| commit 59f4ff2ecff4cef36378928cec891785b402e80c upstream |
| |
| This patch (as1119b) 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> |
| Tested-by: Matthew Frost <artusemrys@sbcglobal.net> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| drivers/usb/storage/transport.c | 17 +++++++++++++++-- |
| 1 file changed, 15 insertions(+), 2 deletions(-) |
| |
| --- a/drivers/usb/storage/transport.c |
| +++ b/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)); |
