usbip: dump the port status difference

At the beginning of vhci_hub_control() function the port
status is saved to show what are the differences between the
previous and the new status. Change the dump function to
really show the differences in the status bit changes: put
a '+' sign before the symbolic name of a bit where a bit
was set, a '-' sign where the bit was cleared and a SPACE
where the bit was not changed. This is similar to the way
"diff -u" shows the changes and easy to understand.
Signed-off-by: NMárton Németh <nm127@freemail.hu>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/staging/usbip/vhci_hcd.c

@@ -92,14 +92,28 @@ static const char * const bit_desc[] = {
 	"R31",			/*31*/
 };
 
-static void dump_port_status(u32 status)
+static void dump_port_status_diff(u32 prev_status, u32 new_status)
 {
 	int i = 0;
-
-	pr_debug("status %08x:", status);
-	for (i = 0; i < 32; i++) {
-		if (status & (1 << i))
-			pr_debug(" %s", bit_desc[i]);
+	u32 bit = 1;
+
+	pr_debug("status prev -> new: %08x -> %08x\n", prev_status, new_status);
+	while (bit) {
+		u32 prev = prev_status & bit;
+		u32 new = new_status & bit;
+		char change;
+
+		if (!prev && new)
+			change = '+';
+		else if (prev && !new)
+			change = '-';
+		else
+			change = ' ';
+
+		if (prev || new)
+			pr_debug(" %c%s\n", change, bit_desc[i]);
+		bit <<= 1;
+		i++;
 	}
 	pr_debug("\n");
 }
@@ -466,8 +480,8 @@ static int vhci_hub_control(struct usb_hcd *hcd, u16 typeReq, u16 wValue,
 		pr_debug("port %d\n", rhport);
 		/* Only dump valid port status */
 		if (rhport >= 0) {
-			dump_port_status(prev_port_status[rhport]);
-			dump_port_status(dum->port_status[rhport]);
+			dump_port_status_diff(prev_port_status[rhport],
+					      dum->port_status[rhport]);
 		}
 	}
 	usbip_dbg_vhci_rh(" bye\n");