usb: gadget: function: printer: Interface is disabled and returns error

After the device is disconnected from the host side, the interface of
the device is reset. If the userspace operates the device again,
an error code should be returned.
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/gadget/function/f_printer.c

@@ -338,6 +338,11 @@ printer_open(struct inode *inode, struct file *fd)
 
 	spin_lock_irqsave(&dev->lock, flags);
 
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return -ENODEV;
+	}
+
 	if (!dev->printer_cdev_open) {
 		dev->printer_cdev_open = 1;
 		fd->private_data = dev;
@@ -430,6 +435,12 @@ printer_read(struct file *fd, char __user *buf, size_t len, loff_t *ptr)
 	mutex_lock(&dev->lock_printer_io);
 	spin_lock_irqsave(&dev->lock, flags);
 
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		mutex_unlock(&dev->lock_printer_io);
+		return -ENODEV;
+	}
+
 	/* We will use this flag later to check if a printer reset happened
 	 * after we turn interrupts back on.
 	 */
@@ -561,6 +572,12 @@ printer_write(struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
 	mutex_lock(&dev->lock_printer_io);
 	spin_lock_irqsave(&dev->lock, flags);
 
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		mutex_unlock(&dev->lock_printer_io);
+		return -ENODEV;
+	}
+
 	/* Check if a printer reset happens while we have interrupts on */
 	dev->reset_printer = 0;
 
@@ -667,6 +684,13 @@ printer_fsync(struct file *fd, loff_t start, loff_t end, int datasync)
 
 	inode_lock(inode);
 	spin_lock_irqsave(&dev->lock, flags);
+
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		inode_unlock(inode);
+		return -ENODEV;
+	}
+
 	tx_list_empty = (likely(list_empty(&dev->tx_reqs)));
 	spin_unlock_irqrestore(&dev->lock, flags);
 
@@ -689,6 +713,13 @@ printer_poll(struct file *fd, poll_table *wait)
 
 	mutex_lock(&dev->lock_printer_io);
 	spin_lock_irqsave(&dev->lock, flags);
+
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		mutex_unlock(&dev->lock_printer_io);
+		return EPOLLERR | EPOLLHUP;
+	}
+
 	setup_rx_reqs(dev);
 	spin_unlock_irqrestore(&dev->lock, flags);
 	mutex_unlock(&dev->lock_printer_io);
@@ -722,6 +753,11 @@ printer_ioctl(struct file *fd, unsigned int code, unsigned long arg)
 
 	spin_lock_irqsave(&dev->lock, flags);
 
+	if (dev->interface < 0) {
+		spin_unlock_irqrestore(&dev->lock, flags);
+		return -ENODEV;
+	}
+
 	switch (code) {
 	case GADGET_GET_PRINTER_STATUS:
 		status = (int)dev->printer_status;