DragonFly On-Line Manual Pages
USB(4) DragonFly Kernel Interfaces Manual USB(4)
usb -- Universal Serial Bus
To compile this driver into the kernel, place the following line in your
kernel configuration file:
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
USB functions can be accessed from userland through the libusb library.
See libusb(3) for more information.
DragonFly provides machine-independent bus support and drivers for USB
devices in host and device side mode.
The usb driver has three layers:
USB Controller (Bus)
The controller attaches to a physical bus like pci(4). The USB bus
attaches to the controller, and the root hub attaches to the controller.
Any devices attached to the bus will attach to the root hub or another
hub attached to the USB bus.
The uhub device will always be present as it is needed for the root hub.
DragonFly provides support for the following devices.
umass(4) Mass Storage Devices, e.g., external disk drives
usfs(4) Mass storage driver for device-side mode
Wired network interfaces
axe(4) ASIX Electronics AX88x7x/760 USB Ethernet driver
udav(4) Davicom DM9601 USB Ethernet driver
Wireless network interfaces
ndis(4) NDIS miniport driver wrapper
rum(4) Ralink Technology RT2501USB/RT2601USB IEEE 802.11
run(4) Ralink Technology RT2700U/RT2800U/RT3000U IEEE
urtwn(4) Realtek RTL8188CU/RTL8192CU IEEE 802.11 driver
Serial and parallel interfaces
u3g(4) support for 3G datacards
uark(4) Arkmicro Technologies ARK3116 based serial adapters
ubsa(4) Belkin serial adapters
ubser(4) support for BWCT console serial adapters
uchcom(4) WinChipHead CH341/CH340 serial adapters
ucom(4) tty support
ucycom(4) Cypress CY7C63743 and CY7C64013 USB to RS232 bridges
ufoma(4) mobile phone support
uftdi(4) serial devices based on the FTDI chips
ugensa(4) generic serial device
uipaq(4) support for iPAQ units
ulpt(4) printer support
umcs(4) serial adapters based on the MCS7820 and MCS7840
umct(4) Magic Control Technology USB-232 based serial
umodem(4) modem support
umoscom(4) serial adapters based on the MCS7703 chip
uplcom(4) Prolific PL-2303/2303X/2303HX serial adapters
uslcom(4) Silicon Laboratories CP2101, CP2102 and CP2103 USB
to serial bridge
uvisor(4) support for the Handspring Visor, a Palmpilot com-
uvscom(4) SUNTAC Slipper U VS-10U serial adapters
Radio receiver devices
ufm(4) Cypress Semiconductor FM Radio
Human Interface Devices
uep(4) eGalax touchscreen driver
uhid(4) generic driver for Human Interface Devices
ukbd(4) keyboards that follow the boot protocol
ums(4) mouse devices
INTRODUCTION TO USB
The USB is a system where external devices can be connected to a PC. The
most common USB speeds are:
Low Speed (1.5MBit/sec)
Full Speed (12MBit/sec)
High Speed (480MBit/sec)
Each USB has a USB controller that is the master of the bus. The physi-
cal communication is simplex which means the host controller only commu-
nicates with one USB device at a time.
There can be up to 127 devices connected to an USB HUB tree. The
addresses are assigned dynamically by the host when each device is
attached to the bus.
Within each device there can be up to 16 endpoints. Each endpoint is
individually addressed and the addresses are static. Each of these end-
points will communicate in one of four different modes: control,
isochronous, bulk, or interrupt. A device always has at least one end-
point. This endpoint has address 0 and is a control endpoint and is used
to give commands to and extract basic data, such as descriptors, from the
device. Each endpoint, except the control endpoint, is unidirectional.
The endpoints in a device are grouped into interfaces. An interface is a
logical unit within a device; e.g. a compound device with both a keyboard
and a trackball would present one interface for each. An interface can
sometimes be set into different modes, called alternate settings, which
affects how it operates. Different alternate settings can have different
endpoints within it.
A device may operate in different configurations. Depending on the con-
figuration, the device may present different sets of endpoints and inter-
The bus enumeration of the USB bus proceeds in several steps:
1. Any interface specific driver can attach to the device.
2. If none is found, generic interface class drivers can attach.
The USB specifications can be found at:
libusb(3), axe(4), ehci(4), ndis(4), ohci(4), pci(4), rum(4), run(4),
u3g(4), uark(4), ubsa(4), ubser(4), uchcom(4), ucom(4), ucycom(4),
udav(4), uep(4), ufm(4), ufoma(4), uftdi(4), ugensa(4), uhci(4), uhid(4),
uipaq(4), ukbd(4), ulpt(4), umass(4), umcs(4), umct(4), umodem(4),
umoscom(4), ums(4), uplcom(4), urtwn(4), usfs(4), uslcom(4), uvisor(4),
uvscom(4), xhci(4), usbconfig(8), usbdi(9)
The usb module complies with the USB 2.0 standard.
The usb module has been inspired by the NetBSD USB stack initially writ-
ten by Lennart Augustsson. The usb module was written by Hans Petter
DragonFly 3.7 March 16, 2014 DragonFly 3.7