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>
diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index cbdcb3c..ea8e316 100644
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -1062,39 +1062,36 @@
/* 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 @@
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 @@
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;