usb: gadget: function: f_fs: Move epfile waitqueue to ffs_data.

There were individual waitqueues for each epfile but eps_enable
would iterate through all of them, resulting in essentially the
same wakeup time.

The waitqueue represents the function being enabled, so a central
waitqueue in ffs_data makes more sense and is less redundant.

Also use wake_up_interruptible to reflect use of
wait_event_interruptible.

Acked-by: Michal Nazarewicz <[e-mail]>
Signed-off-by: Jerry Zhang <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>

drivers/usb/gadget/function/f_fs.c

···
 struct ffs_epfile {
 	/* Protects ep->ep and ep->req. */
 	struct mutex			mutex;
-	wait_queue_head_t		wait;
 
 	struct ffs_data			*ffs;
 	struct ffs_ep			*ep;	/* P: ffs->eps_lock */
···
 		if (file->f_flags & O_NONBLOCK)
 			return -EAGAIN;
 
-		ret = wait_event_interruptible(epfile->wait, (ep = epfile->ep));
+		ret = wait_event_interruptible(
+				epfile->ffs->wait, (ep = epfile->ep));
 		if (ret)
 			return -EINTR;
 	}
···
 		if (file->f_flags & O_NONBLOCK)
 			return -EAGAIN;
 
-		ret = wait_event_interruptible(epfile->wait, (ep = epfile->ep));
+		ret = wait_event_interruptible(
+				epfile->ffs->wait, (ep = epfile->ep));
 		if (ret)
 			return -EINTR;
 	}
···
 		pr_info("%s(): freeing\n", __func__);
 		ffs_data_clear(ffs);
 		BUG_ON(waitqueue_active(&ffs->ev.waitq) ||
-		       waitqueue_active(&ffs->ep0req_completion.wait));
+		       waitqueue_active(&ffs->ep0req_completion.wait) ||
+		       waitqueue_active(&ffs->wait));
 		kfree(ffs->dev_name);
 		kfree(ffs);
 	}
···
 	mutex_init(&ffs->mutex);
 	spin_lock_init(&ffs->eps_lock);
 	init_waitqueue_head(&ffs->ev.waitq);
+	init_waitqueue_head(&ffs->wait);
 	init_completion(&ffs->ep0req_completion);
 
 	/* XXX REVISIT need to update it in some places, or do we? */
···
 	for (i = 1; i <= count; ++i, ++epfile) {
 		epfile->ffs = ffs;
 		mutex_init(&epfile->mutex);
-		init_waitqueue_head(&epfile->wait);
 		if (ffs->user_flags & FUNCTIONFS_VIRTUAL_ADDR)
 			sprintf(epfile->name, "ep%02x", ffs->eps_addrmap[i]);
 		else
···
 	ENTER();
 
 	for (; count; --count, ++epfile) {
-		BUG_ON(mutex_is_locked(&epfile->mutex) ||
-		       waitqueue_active(&epfile->wait));
+		BUG_ON(mutex_is_locked(&epfile->mutex));
 		if (epfile->dentry) {
 			d_delete(epfile->dentry);
 			dput(epfile->dentry);
···
 			break;
 		}
 
-		wake_up(&epfile->wait);
-
 		++ep;
 		++epfile;
 	}
+
+	wake_up_interruptible(&ffs->wait);
 	spin_unlock_irqrestore(&func->ffs->eps_lock, flags);
 
 	return ret;

drivers/usb/gadget/function/u_fs.h

···
 #define FFS_FL_CALL_CLOSED_CALLBACK 0
 #define FFS_FL_BOUND                1
 
+	/* For waking up blocked threads when function is enabled. */
+	wait_queue_head_t		wait;
+
 	/* Active function */
 	struct ffs_function		*func;