Kernel patch to work around deficiencies in usbmon

Pete Zaitcev zaitcev at redhat.com
Mon Jul 11 03:25:39 UTC 2005


Hi, Dave:

We have usbmon enabled now and it's good, but usb-storage moved away
from under me a little bit. It now maps everything for DMA beforehand,
which makes usbmon to miss the SCSI commands and replies.

I am going to address this problem in usbmon, where it belongs, but
it requires some work which is not done.

What do you think about carrying the attached patch for a few months
(I hope to turn around sooner, but you know how that works!)

-- Pete

diff -urp -X dontdiff linux-2.6.12/drivers/usb/storage/transport.c linux-2.6.12-lem/drivers/usb/storage/transport.c
--- linux-2.6.12/drivers/usb/storage/transport.c	2005-06-21 12:58:48.000000000 -0700
+++ linux-2.6.12-lem/drivers/usb/storage/transport.c	2005-07-06 14:00:30.000000000 -0700
@@ -948,8 +948,9 @@ int usb_stor_Bulk_max_lun(struct us_data
 
 int usb_stor_Bulk_transport(struct scsi_cmnd *srb, struct us_data *us)
 {
-	struct bulk_cb_wrap *bcb = (struct bulk_cb_wrap *) us->iobuf;
-	struct bulk_cs_wrap *bcs = (struct bulk_cs_wrap *) us->iobuf;
+	/* Offset into iobuf a little in order to defeat pre-set DMA */
+	struct bulk_cb_wrap *bcb = (struct bulk_cb_wrap *) (us->iobuf + 4);
+	struct bulk_cs_wrap *bcs = (struct bulk_cs_wrap *) (us->iobuf + 4);
 	unsigned int transfer_length = srb->request_bufflen;
 	unsigned int residue;
 	int result;
@@ -960,7 +961,7 @@ int usb_stor_Bulk_transport(struct scsi_
 	/* Take care of BULK32 devices; set extra byte to 0 */
 	if ( unlikely(us->flags & US_FL_BULK32)) {
 		cbwlen = 32;
-		us->iobuf[31] = 0;
+		((unsigned char *)bcb)[31] = 0;
 	}
 
 	/* set up the command wrapper */




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