[PATCH] USB Storage: retry hard errors

This patch started life as as527, and was rediffed by me.

Since the IDE interface doesn't convey much information about types of
errors, many USB-IDE adapters report all low-level errors with SK = 0x04,
which is supposed to be used only for non-recoverable errors.  As a result
the SCSI midlayer doesn't retry the command.  But quite often a retry
would succeed, whereas an unnecessary retry doesn't really hurt anything.

This patch uses a recently-implemented flag to tell the SCSI midlayer that
such hardware errors should be retried.

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

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
index da2bfa944b96..af294bb68c35 100644
--- a/drivers/usb/storage/scsiglue.c
+++ b/drivers/usb/storage/scsiglue.c
@@ -155,6 +155,15 @@ static int slave_configure(struct scsi_device *sdev)
                  * If this device makes that mistake, tell the sd driver. */
                 if (us->flags & US_FL_FIX_CAPACITY)
                         sdev->fix_capacity = 1;
+
+                /* USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
+                 * Hardware Error) when any low-level error occurs,
+                 * recoverable or not.  Setting this flag tells the SCSI
+                 * midlayer to retry such commands, which frequently will
+                 * succeed and fix the error.  The worst this can lead to
+                 * is an occasional series of retries that will all fail. */
+                sdev->retry_hwerror = 1;
+
         } else {
 
                 /* Non-disk-type devices don't need to blacklist any pages