USB(4) BSD Kernel Interfaces Manual USB(4)NAME
usb — Universal Serial Bus driver
SYNOPSIS
ehci* at cardbus? function ?
ehci* at pci? dev ? function ?
ohci* at cardbus? function ?
ohci* at pci? dev ? function ?
slhci* at isa? port ? irq ?
slhci* at pcmcia? function ?
uhci* at cardbus? function ?
uhci* at pci? dev ? function ?
usb* at ehci? flags X
usb* at ohci? flags X
usb* at uhci? flags X
usb* at slhci? flags X
uhub* at usb?
uhub* at uhub? port ? configuration ? interface ? vendor ? product ?
release ?
XX* at uhub? port ? configuration ? interface ? vendor ? product ?
release ?
options USBVERBOSE
#include <dev/usb/usb.h>
#include <dev/usb/usbhid.h>
DESCRIPTION
NetBSD provides machine-independent bus support and drivers for USB
devices.
The NetBSD usb driver has three layers (like scsi(4) and pcmcia(4)): the
controller, the bus, and the device layer. The controller attaches to a
physical bus (like pci(4)). The USB bus attaches to the controller and
the root hub attaches to the bus. Further devices, which may include
further hubs, attach to other hubs. The attachment forms the same tree
structure as the physical USB device tree. For each USB device there may
be additional drivers attached to it.
The uhub device controls USB hubs and must always be present since there
is at least a root hub in any USB system.
The flags argument to the usb device affects the order in which the
device detection happens during cold boot. Normally, only the USB host
controller and the usb device are detected during the autoconfiguration
when the machine is booted. The rest of the devices are detected once
the system becomes functional and the kernel thread for the usb device is
started. Sometimes it is desirable to have a device detected early in
the boot process, e.g., the console keyboard. To achieve this use a
flags value of 1.
NetBSD supports the following machine-independent USB drivers:
Storage devices
umass(4) USB Mass Storage Devices, e.g., external disk drives
Wired network interfaces
aue(4) ADMtek AN986/ADM8511 Pegasus family 10/100 USB Ethernet
device
axe(4) ASIX Electronics AX88172/AX88178/AX88772 10/100/Gigabit
USB Ethernet device
cdce(4) USB Communication Device Class Ethernet device
cue(4) CATC USB-EL1201A USB Ethernet device
kue(4) Kawasaki LSI KL5KUSB101B USB Ethernet device
udav(4) Davicom DM9601 10/100 USB Ethernet device
url(4) Realtek RTL8150L 10/100 USB Ethernet device
Wireless network interfaces
atu(4) Atmel AT76C50x IEEE 802.11b wireless network device
ral(4) Ralink Technology USB IEEE 802.11b/g wireless network
device
rum(4) Ralink Technology USB IEEE 802.11a/b/g wireless network
device
ubt(4) USB Bluetooth dongles
upgt(4) Conexant/Intersil PrismGT SoftMAC USB 802.11b/g wireless
network device
urtwn(4) Realtek RTL8188CU/RTL8192CU USB IEEE 802.11b/g/n wire‐
less network device
zyd(4) ZyDAS ZD1211/ZD1211B USB IEEE 802.11b/g wireless network
device
Serial and parallel interfaces
ubsa(4) Belkin USB serial adapter
uchcom(4) WinChipHead CH341/340 based USB serial adapter
ucom(4) USB tty support
ucycom(4) Cypress microcontroller based USB serial adapter
uftdi(4) FT8U100AX USB serial adapter
ugensa(4) USB generic serial adapter
uhmodem(4) USB Huawei 3G wireless modem device
uipaq(4) iPAQ USB units
ukyopon(4) USB Kyocera AIR-EDGE PHONE device
ulpt(4) USB printer support
umct(4) MCT USB-RS232 USB serial adapter
umodem(4) USB modem support
uplcom(4) Prolific PL-2303 USB serial adapter
uslsa(4) Silicon Laboratories CP2101/CP2102 based USB serial
adapter
uvisor(4) USB Handspring Visor
uvscom(4) SUNTAC Slipper U VS-10U USB serial adapter
Audio devices
uaudio(4) USB audio devices
umidi(4) USB MIDI devices
urio(4) Diamond Multimedia Rio MP3 players
Radio receiver devices
udsbr(4) D-Link DSB-R100 USB radio device
Human Interface Devices
uhid(4) Generic driver for Human Interface Devices
uhidev(4) Base driver for all Human Interface Devices
ukbd(4) USB keyboards that follow the boot protocol
ums(4) USB mouse devices
Miscellaneous devices
stuirda(4) Sigmaltel 4116/4220 USB-IrDA bridge
uep(4) USB eGalax touch-panel
ugen(4) USB generic devices
uirda(4) USB IrDA bridges
upl(4) Prolific based host-to-host adapters
uscanner(4) USB scanner support
usscanner(4) SCSI-over-USB scanners
ustir(4) SigmaTel STIr4200 USB IrDA bridges
utoppy(4) Topfield TF5000PVR range of digital video recorders
uyap(4) USB YAP phone firmware loader
INTRODUCTION TO USB
The USB 1.x is a 12 Mb/s serial bus with 1.5 Mb/s for low speed devices.
USB 2.x handles 480 Mb/s. Each USB has a host controller that is the
master of the bus; all other devices on the bus only speak when spoken
to.
There can be up to 127 devices (apart from the host controller) on a bus,
each with its own address. 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 key‐
board 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‐
faces.
Each device located on a hub has several config(1) locators:
port this is the number of the port on closest upstream hub.
configuration
this is the configuration the device must be in for this
driver to attach. This locator does not set the configura‐
tion; it is iterated by the bus enumeration.
interface this is the interface number within a device that an interface
driver attaches to.
vendor this is the 16 bit vendor id of the device.
product this is the 16 bit product id of the device.
release this is the 16 bit release (revision) number of the device.
The first locator can be used to pin down a particular device according
to its physical position in the device tree. The last three locators can
be used to pin down a particular device according to what device it actu‐
ally is.
The bus enumeration of the USB bus proceeds in several steps:
1. Any device specific driver can attach to the device.
2. If none is found, any device class specific driver can attach.
3. If none is found, all configurations are iterated over. For each
configuration all the interface are iterated over and interface
drivers can attach. If any interface driver attached in a certain
configuration the iteration over configurations is stopped.
4. If still no drivers have been found, the generic USB driver can
attach.
USB CONTROLLER INTERFACE
Use the following to get access to the USB specific structures and
defines.
#include <dev/usb/usb.h>
The /dev/usbN can be opened and a few operations can be performed on it.
The poll(2) system call will say that I/O is possible on the controller
device when a USB device has been connected or disconnected to the bus.
The following ioctl(2) commands are supported on the controller device:
USB_DEVICEINFO struct usb_device_info
This command can be used to retrieve some information about a
device on the bus. The addr field should be filled before the
call and the other fields will be filled by information about the
device on that address. Should no such device exist an error is
reported.
struct usb_device_info {
uint8_t udi_bus;
uint8_t udi_addr;
usb_event_cookie_t udi_cookie;
char udi_product[USB_MAX_ENCODED_STRING_LEN];
char udi_vendor[USB_MAX_ENCODED_STRING_LEN];
char udi_release[8];
char udi_serial[USB_MAX_ENCODED_STRING_LEN];
uint16_t udi_productNo;
uint16_t udi_vendorNo;
uint16_t udi_releaseNo;
uint8_t udi_class;
uint8_t udi_subclass;
uint8_t udi_protocol;
uint8_t udi_config;
uint8_t udi_speed;
#define USB_SPEED_LOW 1
#define USB_SPEED_FULL 2
#define USB_SPEED_HIGH 3
int udi_power;
int udi_nports;
char udi_devnames[USB_MAX_DEVNAMES][USB_MAX_DEVNAMELEN];
uint8_t udi_ports[16];
#define USB_PORT_ENABLED 0xff
#define USB_PORT_SUSPENDED 0xfe
#define USB_PORT_POWERED 0xfd
#define USB_PORT_DISABLED 0xfc
};
The product, vendor, release, and serial fields contain self-
explanatory descriptions of the device.
The class field contains the device class.
The config field shows the current configuration of the device.
The lowspeed field is set if the device is a USB low speed
device.
The power field shows the power consumption in milli-amps drawn
at 5 volts, or zero if the device is self powered.
If the device is a hub the nports field is non-zero and the ports
field contains the addresses of the connected devices. If no
device is connected to a port one of the USB_PORT_* values indi‐
cates its status.
USB_DEVICESTATS struct usb_device_stats
This command retrieves statistics about the controller.
struct usb_device_stats {
u_long uds_requests[4];
};
The requests field is indexed by the transfer kind, i.e. UE_*,
and indicates how many transfers of each kind have been completed
by the controller.
USB_REQUEST struct usb_ctl_request
This command can be used to execute arbitrary requests on the
control pipe. This is DANGEROUS and should be used with great
care since it can destroy the bus integrity.
The include file <dev/usb/usb.h> contains definitions for the types used
by the various ioctl(2) calls. The naming convention of the fields for
the various USB descriptors exactly follows the naming in the USB speci‐
fication. Byte sized fields can be accessed directly, but word (16 bit)
sized fields must be access by the UGETW(field) and USETW(field, value)
macros to handle byte order and alignment properly.
The include file <dev/usb/usbhid.h> similarly contains the definitions
for Human Interface Devices (HID).
USB EVENT INTERFACE
All USB events are reported via the /dev/usb device. This devices can be
opened for reading and each read(2) will yield an event record (if some‐
thing has happened). The poll(2) system call can be used to determine if
an event record is available for reading.
The event record has the following definition:
struct usb_event {
int ue_type;
#define USB_EVENT_CTRLR_ATTACH 1
#define USB_EVENT_CTRLR_DETACH 2
#define USB_EVENT_DEVICE_ATTACH 3
#define USB_EVENT_DEVICE_DETACH 4
#define USB_EVENT_DRIVER_ATTACH 5
#define USB_EVENT_DRIVER_DETACH 6
struct timespec ue_time;
union {
struct {
int ue_bus;
} ue_ctrlr;
struct usb_device_info ue_device;
struct {
usb_event_cookie_t ue_cookie;
char ue_devname[16];
} ue_driver;
} u;
};
The ue_type field identifies the type of event that is described. The
possible events are attach/detach of a host controller, a device, or a
device driver. The union contains information pertinent to the different
types of events.
The ue_bus contains the number of the USB bus for host controller events.
The ue_device record contains information about the device in a device
event event.
The ue_cookie is an opaque value that uniquely determines which device a
device driver has been attached to (i.e., it equals the cookie value in
the device that the driver attached to). The ue_devname contains the
name of the device (driver) as seen in, e.g., kernel messages.
Note that there is a separation between device and device driver events.
A device event is generated when a physical USB device is attached or
detached. A single USB device may have zero, one, or many device drivers
associated with it.
KERNEL THREADS
For each USB bus, i.e., for each host controller, there is a kernel
thread that handles attach and detach of devices on that bus. The thread
is named usbN where N is the bus number.
In addition there is a kernel thread, usbtask, which handles various
minor tasks that are initiated from an interrupt context, but need to
sleep, e.g., time-out abort of transfers.
SEE ALSOusbhidaction(1), usbhidctl(1), cardbus(4), ehci(4), isa(4), ohci(4),
pci(4), pcmcia(4), slhci(4), uhci(4), usbdevs(8)
Universal Serial Bus Specifications Documents,
http://www.usb.org/developers/docs/.
HISTORY
The usb driver appeared in NetBSD 1.4.
BUGS
There should be a serial number locator, but NetBSD does not have string
valued locators.
BSD January 22, 2012 BSD
