usb: gadget: functionfs: Factorize wait-for-endpoint code

This exact same code was duplicated in two different places.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20240130122340.54813-3-paul@crapouillou.netSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/f_fs.c

@@ -934,31 +934,44 @@ static ssize_t __ffs_epfile_read_data(struct ffs_epfile *epfile,
 	return ret;
 }
 
-static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
+static struct ffs_ep *ffs_epfile_wait_ep(struct file *file)
 {
 	struct ffs_epfile *epfile = file->private_data;
-	struct usb_request *req;
 	struct ffs_ep *ep;
-	char *data = NULL;
-	ssize_t ret, data_len = -EINVAL;
-	int halt;
-
-	/* Are we still active? */
-	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
-		return -ENODEV;
+	int ret;
 
 	/* Wait for endpoint to be enabled */
 	ep = epfile->ep;
 	if (!ep) {
 		if (file->f_flags & O_NONBLOCK)
-			return -EAGAIN;
+			return ERR_PTR(-EAGAIN);
 
 		ret = wait_event_interruptible(
 				epfile->ffs->wait, (ep = epfile->ep));
 		if (ret)
-			return -EINTR;
+			return ERR_PTR(-EINTR);
 	}
 
+	return ep;
+}
+
+static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
+{
+	struct ffs_epfile *epfile = file->private_data;
+	struct usb_request *req;
+	struct ffs_ep *ep;
+	char *data = NULL;
+	ssize_t ret, data_len = -EINVAL;
+	int halt;
+
+	/* Are we still active? */
+	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE))
+		return -ENODEV;
+
+	ep = ffs_epfile_wait_ep(file);
+	if (IS_ERR(ep))
+		return PTR_ERR(ep);
+
 	/* Do we halt? */
 	halt = (!io_data->read == !epfile->in);
 	if (halt && epfile->isoc)
@@ -1280,16 +1293,9 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
 		return -ENODEV;
 
 	/* Wait for endpoint to be enabled */
-	ep = epfile->ep;
-	if (!ep) {
-		if (file->f_flags & O_NONBLOCK)
-			return -EAGAIN;
-
-		ret = wait_event_interruptible(
-				epfile->ffs->wait, (ep = epfile->ep));
-		if (ret)
-			return -EINTR;
-	}
+	ep = ffs_epfile_wait_ep(file);
+	if (IS_ERR(ep))
+		return PTR_ERR(ep);
 
 	spin_lock_irq(&epfile->ffs->eps_lock);