NetBSD/share/man/man4/usb.4

.\" $NetBSD: usb.4,v 1.3 1998/07/26 22:22:26 augustss Exp $
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.Dd July 12, 1998
.Dt USB 4
.Os
.Sh NAME
.Nm usb
.Nd introduction to USB support
.Sh SYNOPSIS
.Cd "uhci*   at pci? function?"
.Cd "ohci*   at pci? function?"
.Cd "usb*    at uhci?"
.Cd "usb*    at ohci?"
.Cd "uhub*   at usb?"
.Cd "uhub*   at uhub? port ?"
.Cd "XX*     at uhub? port ?"
.Pp
.Sh INTRODUCTION
.Nx
provides machine-independent bus support and
drivers for USB devices.
.Pp
The
.Nx
driver has three layers (like
.Xr scsi 4
and
.Xr pcmcia 4 ):
the controller, the bus, and the device layer.
The controller attaches to a physical bus (like
.Xr pci 4 ).
The USB bus attaches to the controller and the root hub attaches
to the controller.  Further devices, which includes 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 further drivers attached to it.
.Pp
The
.Cm uhub
device controls USB hubs and must always be present (since there
is at least a root hub in any USB system).
.Pp
.Sh INTRODUCTION TO USB
The USB is a 12Mb/s serial bus (1.5 Mb/s for low speed devices).
Each USB bus has a host controller that is the master of the bus;
all other devices on the bus only speak when spoken to.
.Pp
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 the device is attached to the bus.
.Pp
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 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 control endpoints, is unidirectional.
.Pp
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.
.Pp
A device may operate in different configurations.  Depending on the
configuration the device may present different sets of endpoints
and interfaces.
.Sh USB CONTROLLER INTERFACE
Use the following to get access to the USB specific structurs and defines.
.Bd -literal 
#include <sys/dev/usb.h>
.Ed
.Pp
The
.Pa /dev/usbN
can be opened and a few operations can be performed on it.
The
.Xr 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.
.Pp
The following
.Xr ioctl 2
commands are supported on the controller device:
.Bl -tag -width indent -compact
.It Dv USB_DISCOVER
This command will cause a complete bus discovery to be initiated.
If any devices attached or detached from the bus they will be
processed during this command.  This is the only way that new
devices are found on the bus.
.It Dv USB_DEVICEINFO (struct usb_device_info)
This command can be used to retrieve some information about a device
on the bus.  The 
.Va 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.
.Bd -literal
struct usb_device_info {
	uByte	addr;		/* device address */
	char	product[USB_MAX_STRING_LEN];
	char	vendor[USB_MAX_STRING_LEN];
	char	revision[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
};
.Ed
The
.Va product ,
.Va vendor ,
and
.Va revision
fields contain (self-explanatory) descriptions of the device.
The
.Va class
field contans the device class.
The
.Va config
field shows the current configuration of the device.
The
.Va lowspeed
field
is set if the device is a USB low speed device.
The
.Va power
field shows the power consumption in mA (drawn a 5V), or 0 if
the device is self powered.
.Pp
If the device is a hub the
.Va nports
field is non-zero and the
.Va ports
field contains the addresses of the connected devices.
If no device is connected to a port one of the
.Va USB_PORT_*
values indicates its status.
.It Dv USB_DEVICESTATS (struct usb_device_stats)
.Bd -literal
This command retrieves statisctics about the controller.
struct usb_device_stats {
	u_long	requests[4];
};
.Ed
The
.Va requests
field is indexed by the transfer kind, i.e.,
.Va UE_* ,
and indicates how many transfers of each kind that has been completed
for the controller.
.It Dv 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 integrety.
.El
.Sh SEE ALSO
.Xr pci 4 ,
.Xr uaudio 4 ,
.Xr ugen 4 ,
.Xr uhid 4 ,
.Xr ukbd 4 ,
.Xr ulpt 4 ,
.Xr ums 4 ,
.Xr usbd 8 ,
.Xr usbdevs 8
.Sh HISTORY
The
.Nm
driver
appeared in
.Nx 1.4 .