Composite devices

Adding two class functions to one device makes it composite - the bundled msc_cdc_device example is a disk plus a serial console for it, and the C-only cdc_dfu_device is a serial port plus firmware upgrade. The host sees both functions at once - one plug, a drive and a serial port.

Declare the device composite before adding the functions, so the classes emit the Interface Association Descriptors that Windows needs to keep each function's interfaces together:

PythonC

import usbip
from usbip import USBDevice
from usbip.classes.device import CDCACM, MSC

dev = USBDevice(0x1209, 0x0005, product="USBIP MSC+CDC")
dev.set_composite()                  # BEFORE adding the functions

console = dev.add(CDCACM(on_rx=on_rx, name="Disk console"))
disk = dev.add(MSC(store))           # the block backend from the MSC recipe

transport = usbip.USBIP("0.0.0.0", 3240)
dev.plug(via=transport)

usbip_device *dev = usbip_device_create(0x1209, 0x0005);
usbip_device_set_composite(dev);     /* BEFORE adding the functions */

cdc_acm_opts cops = { .on_rx = on_rx, .name = "Disk console" };
cdc_port *console = cdc_acm_add(dev, &cops);

msc_opts mops = { /* block callbacks over the image file */ };
msc_disk *disk = msc_add(dev, &mops);

usbip_device_plug(dev);

Each class asks for the endpoint addresses it would use alone, so on one device they collide - the core relocates the later ones onto free numbers, and each class keeps the pipe it was handed. You never assign endpoint addresses yourself.

How functions group interfaces, when the EF/02/01 composite device class triple is required, and how per-function Microsoft OS descriptors behave on a composite device are covered in Components → functions & interfaces.

A composite is one device with several functions. To serve several separate devices from one program instead - each with its own VID/PID, busid and attach - see Multiple devices.

Runnable program: examples/cdc_hid_device.py (and its C twin) - a serial port plus a HID consumer control (media keys) on one device, and the pair the cross-language test holds byte-identical. See Examples.