usb - introduction to Universal Serial Bus support
ehci* at pci? dev ? function ?
uhci* at pci? dev ? function ?
ohci* at pci? dev ? function ?
usb* at ehci? flags 0x00
usb* at uhci? flags 0x00
usb* at ohci? flags 0x00
uhub* at usb?
uhub* at uhub? port ? configuration ? interface ? vendor ?
#include <dev/usb/usb.h>
#include <dev/usb/usbhid.h>
OpenBSD provides machine-independent bus support and drivers
for Universal
Serial Bus (USB) devices.
The OpenBSD 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 controller. 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 one root hub in any USB system.
The flags are used to specify if the devices on the USB bus
should be
probed early in the boot process. If the flags are specified with a value
of 1, the USB bus will be probed when the USB host device
is attached
instead of waiting until kernel processes start running.
This is useful
for USB console keyboards so that the keyboard is attached
before getting
the root prompt on ``boot -a''.
OpenBSD includes machine-independent USB drivers, sorted by
device type
and driver name:
Storage devices [Toc] [Back]
umass(4) USB Mass Storage Devices, e.g., external
disk drives.
Ethernet adapters [Toc] [Back]
aue(4) ADMtek AN986 / ADM8511 Pegasus family USB
Ethernet interfaces.
axe(4) ASIX Electronics AX88172 USB Ethernet interfaces.
cdce(4) USB Host-to-Host (aka USB-to-USB) bridges
based on the
USB Communication Device Class (CDC) and
Ethernet subclass.
cue(4) CATC USB-EL1201A-based Ethernet interfaces.
kue(4) Kawasaki LSI KL5KUSB101B-based Ethernet interfaces.
url(4) Realtek RTL8150L-based Ethernet interfaces.
wi(4) WaveLAN/IEEE, PRISM 2-3 and Spectrum24
802.11DS wireless
network interfaces.
Serial and parallel interfaces [Toc] [Back]
ubsa(4) Belkin serial adapters.
ucom(4) Serial port-like devices.
uftdi(4) FTDI FT8U100AX-based serial adapters.
ulpt(4) USB Printers.
umct(4) MCT USB-RS232 serial adapters.
umodem(4) USB Modems.
uplcom(4) Prolific PL-2303 serial adapters.
uvscom(4) SUNTAC Slipper U VS-10U serial adapters.
Audio devices [Toc] [Back]
uaudio(4) Audio devices.
umidi(4) USB MIDI devices.
urio(4) Diamond Multimedia Rio MP3 players.
Radio receiver devices [Toc] [Back]
udsbr(4) D-Link DSB-R100 USB radio.
Human Interface Devices [Toc] [Back]
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 [Toc] [Back]
ugen(4) Generic driver for unknown USB devices.
upl(4) Prolific based host-to-host adapters.
uscanner(4) USB scanners.
usscanner(4) SCSI-over-USB scanners.
uvisor(4) Handspring Visor.
uyap(4) YAP phone firmware loader.
The USB is a 12 Mb/s serial bus (1.5 Mb/s for low speed devices). 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 endpoints
will communicate in one of four different modes: control,
isochronous, bulk, or interrupt. A device always has at
least one endpoint.
This is a control endpoint at address 0 and is used
to give commands
to the device 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 configuration
the device may present different sets of endpoints and interfaces.
Each device located on a hub has several config(8) locators:
port Number of the port on closest upstream hub.
configuration Configuration the device must be in for this
driver to attach.
This locator does not set the configuration; it is
iterated by the bus enumeration.
interface Interface number within a device that an interface driver
attaches to.
vendor 16-bit vendor ID of the device.
product 16-bit product ID of the device.
release 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 actually
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 interfaces 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 [Toc] [Back] Use the following to get access to the USB specific structures and defines.
#include <dev/usb/usb.h>
The /dev/usbN device 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 {
uByte addr; /* device address */
char product[USB_MAX_STRING_LEN];
char vendor[USB_MAX_STRING_LEN];
char release[8];
uByte class;
uByte config;
uByte lowspeed;
int power;
int nports;
uByte 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, and release 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 indicates
its status.
USB_DEVICESTATS struct usb_device_stats
This command retrieves statistics about the controller.
struct usb_device_stats {
u_long requests[4];
};
The requests field is indexed by the transfer kind,
i.e. UE_*,
and indicates how many transfers of each kind that
has 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 specification.
Byte sized fields can be accessed directly, but
word (16-bit)
sized fields must be accessed 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).
usbhidaction(1), usbhidctl(1), aue(4), axe(4), cardbus(4),
cdce(4),
cue(4), eisa(4), intro(4), isa(4), isapnp(4), kue(4),
pci(4), pcmcia(4),
uaudio(4), ubsa(4), ucom(4), udsbr(4), uftdi(4), ugen(4),
uhid(4),
uhidev(4), uhub(4), ukbd(4), ulpt(4), umass(4), umct(4),
umidi(4),
umodem(4), ums(4), upl(4), uplcom(4), urio(4), url(4), uscanner(4),
usscanner(4), uvisor(4), uvscom(4), uyap(4), wi(4), usbdevs(8)
The USB specifications can be found at:
http://www.usb.org/developers/docs/
The usb driver appeared in OpenBSD 2.6.
There should be a serial number locator, but OpenBSD does
not have string
valued locators.
OpenBSD 3.6 July 12, 1998
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