USB: gadgetfs simplifications

This simplifies event reading by eliminating arithmetic and being
more direct/obvious, and tweaks some debug messages slightly.
The math elimination will change timings, sometimes enough to
allow a race to appear.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 13 insertions, 16 deletions

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index cbdcb3c10c5e..ea8e3160d05e 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -1062,39 +1062,36 @@ scan:
         /* return queued events right away */
         if (dev->ev_next != 0) {
                 unsigned                i, n;
-                int                     tmp = dev->ev_next;
 
-                len = min (len, tmp * sizeof (struct usb_gadgetfs_event));
                 n = len / sizeof (struct usb_gadgetfs_event);
+                if (dev->ev_next < n)
+                        n = dev->ev_next;
 
-                /* ep0 can't deliver events when STATE_DEV_SETUP */
+                /* ep0 i/o has special semantics during STATE_DEV_SETUP */
                 for (i = 0; i < n; i++) {
                         if (dev->event [i].type == GADGETFS_SETUP) {
-                                len = i + 1;
-                                len *= sizeof (struct usb_gadgetfs_event);
-                                n = 0;
+                                dev->state = STATE_DEV_SETUP;
+                                n = i + 1;
                                 break;
                         }
                 }
                 spin_unlock_irq (&dev->lock);
+                len = n * sizeof (struct usb_gadgetfs_event);
                 if (copy_to_user (buf, &dev->event, len))
                         retval = -EFAULT;
                 else
                         retval = len;
                 if (len > 0) {
-                        len /= sizeof (struct usb_gadgetfs_event);
-
                         /* NOTE this doesn't guard against broken drivers;
                          * concurrent ep0 readers may lose events.
                          */
                         spin_lock_irq (&dev->lock);
-                        dev->ev_next -= len;
-                        if (dev->ev_next != 0)
-                                memmove (&dev->event, &dev->event [len],
+                        if (dev->ev_next > n) {
+                                memmove(&dev->event[0], &dev->event[n],
                                         sizeof (struct usb_gadgetfs_event)
-                                                * (tmp - len));
-                        if (n == 0)
-                                dev->state = STATE_DEV_SETUP;
+                                                * (dev->ev_next - n));
+                        }
+                        dev->ev_next -= n;
                         spin_unlock_irq (&dev->lock);
                 }
                 return retval;
@@ -1149,7 +1146,7 @@ next_event (struct dev_data *dev, enum usb_gadgetfs_event_type type)
                 for (i = 0; i != dev->ev_next; i++) {
                         if (dev->event [i].type != type)
                                 continue;
-                        DBG (dev, "discard old event %d\n", type);
+                        DBG(dev, "discard old event[%d] %d\n", i, type);
                         dev->ev_next--;
                         if (i == dev->ev_next)
                                 break;
@@ -1162,9 +1159,9 @@ next_event (struct dev_data *dev, enum usb_gadgetfs_event_type type)
         default:
                 BUG ();
         }
+        VDEBUG(dev, "event[%d] = %d\n", dev->ev_next, type);
         event = &dev->event [dev->ev_next++];
         BUG_ON (dev->ev_next > N_EVENT);
-        VDEBUG (dev, "ev %d, next %d\n", type, dev->ev_next);
         memset (event, 0, sizeof *event);
         event->type = type;
         return event;