linux-kernel - [PATCH] USB: debugging code shouldn't alter control flow

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Date:	Thu, 2 Feb 2012 15:38:14 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Greg KH <greg@...ah.com>
cc:	Keith Packard <keithp@...thp.com>, Pavel Machek <pavel@....cz>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>
Subject: [PATCH] USB: debugging code shouldn't alter control flow

People have complained that debugging code shouldn't alter the flow of
control; it should restrict itself to printing out warnings and error
messages.  Bowing to popular opinion, this patch (as1518) changes the
debugging checks in usb_submit_urb() to follow this guideline.

Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Reported-by: Keith Packard <keithp@...thp.com>
CC: Pavel Machek <pavel@....cz>

---

 drivers/usb/core/urb.c |   21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

Index: usb-3.3/drivers/usb/core/urb.c
===================================================================
--- usb-3.3.orig/drivers/usb/core/urb.c
+++ usb-3.3/drivers/usb/core/urb.c
@@ -403,20 +403,17 @@ int usb_submit_urb(struct urb *urb, gfp_
 	 * cause problems in HCDs if they get it wrong.
 	 */
 	{
-	unsigned int	orig_flags = urb->transfer_flags;
 	unsigned int	allowed;
 	static int pipetypes[4] = {
 		PIPE_CONTROL, PIPE_ISOCHRONOUS, PIPE_BULK, PIPE_INTERRUPT
 	};
 
 	/* Check that the pipe's type matches the endpoint's type */
-	if (usb_pipetype(urb->pipe) != pipetypes[xfertype]) {
-		dev_err(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
+	if (usb_pipetype(urb->pipe) != pipetypes[xfertype])
+		dev_WARN(&dev->dev, "BOGUS urb xfer, pipe %x != type %x\n",
 			usb_pipetype(urb->pipe), pipetypes[xfertype]);
-		return -EPIPE;		/* The most suitable error code :-) */
-	}
 
-	/* enforce simple/standard policy */
+	/* Check against a simple/standard policy */
 	allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_INTERRUPT | URB_DIR_MASK |
 			URB_FREE_BUFFER);
 	switch (xfertype) {
@@ -435,14 +432,12 @@ int usb_submit_urb(struct urb *urb, gfp_
 		allowed |= URB_ISO_ASAP;
 		break;
 	}
-	urb->transfer_flags &= allowed;
+	allowed &= urb->transfer_flags;
 
-	/* fail if submitter gave bogus flags */
-	if (urb->transfer_flags != orig_flags) {
-		dev_err(&dev->dev, "BOGUS urb flags, %x --> %x\n",
-			orig_flags, urb->transfer_flags);
-		return -EINVAL;
-	}
+	/* warn if submitter gave bogus flags */
+	if (allowed != urb->transfer_flags)
+		dev_WARN(&dev->dev, "BOGUS urb flags, %x --> %x\n",
+			urb->transfer_flags, allowed);
 	}
 #endif
 	/*

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