HID: avoid '\0' in hid debugfs events file

When dumping /sys/kernel/debug/hid/$device/events '\0' characters show up
(invisible if cat to console but shown by less or while looking at a dump
 file).  These are due to hid_debug_event() adding strlen()+1 bytes to the ring
buffer (e.g. including the trailing '\0').  Any roll-over causes a '\0' as well
as hid_debug_event() handles the ring buffers with HID_DEBUG_BUFSIZE-1 size
while hid_debug_events_read() handles it with full HID_DEBUG_BUFSIZE size.
Signed-off-by: NBruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

drivers/hid/hid-debug.c

@@ -564,10 +564,10 @@ void hid_debug_event(struct hid_device *hdev, char *buf)
 	struct hid_debug_list *list;
 
 	list_for_each_entry(list, &hdev->debug_list, node) {
-		for (i = 0; i <= strlen(buf); i++)
-			list->hid_debug_buf[(list->tail + i) % (HID_DEBUG_BUFSIZE - 1)] =
+		for (i = 0; i < strlen(buf); i++)
+			list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] =
 				buf[i];
-		list->tail = (list->tail + i) % (HID_DEBUG_BUFSIZE - 1);
+		list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;
         }
 }
 EXPORT_SYMBOL_GPL(hid_debug_event);