libusb: implement libusb_wrap_sys_device

The libusb_wrap_sys_device function can wrap an opened fd from the
system into a libusb handler. However, in FreeBSD's libusb implementation, a
USB device contains two fds: one for control transfers and another for
normal (bulk, interrupt, isochronous) transfers.

This design makes it impossible for FreeBSD to implement this function
without exposing a different structure in libusb.h to provide two fds.
Therefore, we return LIBUSB_ERROR_NOT_SUPPORTED to maintain API
compatibility.

Approved by:    makrj (mentor), lwhsu (mentor)
Sponsored by:   The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D51739

lib/libusb/libusb.3

@@ -209,6 +209,14 @@ Decrement the reference counter of the device
 .Fa dev .
 .Pp
 .Ft int
+.Fn libusb_wrap_sys_device "libusb_context *ctx" "intptr_t sys_dev" "libusb_device_handle **dev_handle"
+This function creates a libusb handler from a previously opened fd
+.Fa sys_dev .
+This function is provided for compatibility and is currently unimplemented.
+It always returns
+.Dv LIBUSB_ERROR_NOT_SUPPORTED .
+.Pp
+.Ft int
 .Fn libusb_open "libusb_device *dev" "libusb_device_handle **devh"
 Open a device and obtain a device_handle.
 Returns 0 on success,

lib/libusb/libusb.h

@@ -506,6 +506,7 @@ int	libusb_get_max_packet_size(libusb_device * dev, uint8_t endpoint);
 int	libusb_get_max_iso_packet_size(libusb_device * dev, uint8_t endpoint);
 libusb_device *libusb_ref_device(libusb_device * dev);
 void	libusb_unref_device(libusb_device * dev);
+int	libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev, libusb_device_handle **dev_handle);
 int	libusb_open(libusb_device * dev, libusb_device_handle ** devh);
 libusb_device_handle *libusb_open_device_with_vid_pid(libusb_context * ctx, uint16_t vendor_id, uint16_t product_id);
 void	libusb_close(libusb_device_handle * devh);

lib/libusb/libusb10.c

@@ -1918,3 +1918,10 @@ libusb_dev_mem_free(libusb_device_handle *devh, unsigned char *buffer,
 {
 	return (LIBUSB_ERROR_NOT_SUPPORTED);
 }
+
+int
+libusb_wrap_sys_device(libusb_context *ctx, intptr_t sys_dev,
+    libusb_device_handle **dev_handle)
+{
+	return (LIBUSB_ERROR_NOT_SUPPORTED);
+}