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Commit 0864c7a9 authored by David Brownell's avatar David Brownell Committed by Greg Kroah-Hartman
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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: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 7489d149

drivers/usb/gadget/inode.c

+13 −16
Original line number Diff line number Diff line
@@ -1062,39 +1062,36 @@ ep0_read (struct file *fd, char __user *buf, size_t len, loff_t *ptr) 
	/* 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;