usb: Reattach kernel driver on close

This releases the usb interface and restores the kernel driver that was
detached when opening the device. This allows other programs to make use
of the tty device when qdl finishes.

Signed-off-by: Jerry Zhang <[email protected]>

Author: jerry-skydio

usb.c

@@ -20,6 +20,7 @@ struct qdl_device_usb {
 
 	int in_ep;
 	int out_ep;
+	int intf;
 
 	size_t in_maxpktsize;
 	size_t out_maxpktsize;
@@ -156,6 +157,7 @@ static int usb_try_open(libusb_device *dev, struct qdl_device_usb *qdl, const ch
 		qdl->usb_handle = handle;
 		qdl->in_ep = in;
 		qdl->out_ep = out;
+		qdl->intf = ifc->bInterfaceNumber;
 		qdl->in_maxpktsize = in_size;
 		qdl->out_maxpktsize = out_size;
 
@@ -227,6 +229,8 @@ static void usb_close(struct qdl_device *qdl)
 {
 	struct qdl_device_usb *qdl_usb = container_of(qdl, struct qdl_device_usb, base);
 
+	libusb_release_interface(qdl_usb->usb_handle, qdl_usb->intf);
+	libusb_attach_kernel_driver(qdl_usb->usb_handle, qdl_usb->intf);
 	libusb_close(qdl_usb->usb_handle);
 	libusb_exit(NULL);
 }