UGEN(4) BSD Kernel Interfaces Manual UGEN(4)NAMEugen — USB generic device support
SYNOPSIS
device ugenDESCRIPTION
The ugen driver provides support for all USB devices that do not have a
special driver. It supports access to all parts of the device, but not
in a way that is as convenient as a special purpose driver.
There can be up to 127 USB devices connected to a USB bus. Each USB
device can have up to 16 endpoints. Each of these endpoints will commu‐
nicate in one of four different modes: control, isochronous, bulk, or
interrupt. Each of the endpoints will have a different device node. The
four least significant bits in the minor device number determines which
endpoint the device accesses and the rest of the bits determines which
USB device.
If an endpoint address is used both for input and output the device can
be opened for both read or write.
To find out what endpoints that exist there are a series of ioctl(2)
operation on the control endpoint that returns the USB descriptors of the
device, configurations, interfaces, and endpoints.
The control transfer mode can only happen on the control endpoint which
is always endpoint 0. The control endpoint accepts request and may
respond with an answer to such request. Control request are issued by
ioctl(2) calls.
The bulk transfer mode can be in or out depending on the endpoint. To
perform I/O on a bulk endpoint read(2) and write(2) should be used. All
I/O operations on a bulk endpoint are unbuffered.
The interrupt transfer mode can only be in. To perform input from an
interrupt endpoint read(2) should be used. A moderate amount of buffer‐
ing is done by the driver.
All endpoints handle the following ioctl(2) calls:
USB_SET_SHORT_XFER (int)
Allow short read transfer. Normally a transfer from the device
which is shorter than the request specified is reported as an
error.
USB_SET_TIMEOUT (int)
Set the timeout on the device operations, the time is specified
in milliseconds. The value 0 is used to indicate that there is
no timeout.
The control endpoint (endpoint 0) handles the following ioctl(2) calls:
USB_GET_CONFIG (int)
Get the device configuration number.
USB_SET_CONFIG (int)
Set the device into the given configuration number.
This operation can only be performed when the control endpoint is
the sole open endpoint.
USB_GET_ALTINTERFACE (struct usb_alt_interface)
Get the alternative setting number for the interface with the
given index. The config_index is ignored in this call.
struct usb_alt_interface {
int config_index;
int interface_index;
int alt_no;
};
USB_SET_ALTINTERFACE (struct usb_alt_interface)
Set the alternative setting to the given number in the interface
with the given index. The config_index is ignored in this call.
This operation can only be performed when no endpoints for the
interface are open.
USB_GET_NO_ALT (struct usb_alt_interface)
Return the number of different alternate settings in the alt_no
field.
USB_GET_DEVICE_DESC (usb_device_descriptor_t)
Return the device descriptor.
USB_GET_CONFIG_DESC (struct usb_config_desc)
Return the descriptor for the configuration with the given index.
For convenience the current configuration can be specified by
USB_CURRENT_CONFIG_INDEX.
struct usb_config_desc {
int config_index;
usb_config_descriptor_t desc;
};
USB_GET_INTERFACE_DESC (struct usb_interface_desc)
Return the interface descriptor for an interface specified by its
configuration index, interface index, and alternative index. For
convenience the current alternative can be specified by
USB_CURRENT_ALT_INDEX.
struct usb_interface_desc {
int config_index;
int interface_index;
int alt_index;
usb_interface_descriptor_t desc;
};
USB_GET_ENDPOINT_DESC (struct usb_endpoint_desc)
Return the endpoint descriptor for the endpoint specified by its
configuration index, interface index, alternative index, and end‐
point index.
struct usb_endpoint_desc {
int config_index;
int interface_index;
int alt_index;
int endpoint_index;
usb_endpoint_descriptor_t desc;
};
USB_GET_FULL_DESC (struct usb_full_desc)
Return all the descriptors for the given configuration.
struct usb_full_desc {
int config_index;
u_int size;
u_char *data;
};
The data field should point to a memory area of the size given in
the size field. The proper size can be determined by first issu‐
ing a USB_GET_CONFIG_DESC and inspecting the wTotalLength field.
USB_GET_STRING_DESC (struct usb_string_desc)
Get a string descriptor for the given language ID and string
index.
struct usb_string_desc {
int string_index;
int language_id;
usb_string_descriptor_t desc;
};
USB_DO_REQUEST (struct usb_ctl_request)
Send a USB request to the device on the control endpoint. Any
data sent to/from the device is located at data. The size of the
transferred data is determined from the request. The addr field
is ignored in this call. The flags field can be used to flag
that the request is allowed to be shorter than the requested
size, and the actlen will contain the actual size on completion.
struct usb_ctl_request {
int addr;
usb_device_request_t request;
void *data;
int flags;
#define USBD_SHORT_XFER_OK 0x04 /* allow short reads */
int actlen; /* actual length transferred */
};
This is a dangerous operation in that it can perform arbitrary
operations on the device. Some of the most dangerous (e.g.,
changing the device address) are not allowed.
USB_GET_DEVICEINFO (struct usb_device_info)
Get an information summary for the device. This call will not
issue any USB transactions.
Note that there are two different ways of addressing configurations,
interfaces, alternatives, and endpoints: by index or by number. The
index is the ordinal number (starting from 0) of the descriptor as pre‐
sented by the device. The number is the respective number of the entity
as found in its descriptor. Enumeration of descriptors use the index,
getting and setting typically uses numbers.
Example: all endpoints (except the control endpoint) for the current con‐
figuration can be found by iterating the interface_index from 0 to
config_desc->bNumInterface-1 and for each of these iterating the
endpoint_index from 0 to interface_desc->bNumEndpoints. The config_index
should set to USB_CURRENT_CONFIG_INDEX and alt_index should be set to
USB_CURRENT_ALT_INDEX.
FILES
/dev/ugenN.EE Endpoint EE of device N.
SEE ALSOusb(4)HISTORY
The ugen driver appeared in NetBSD 1.4.
BSD July 12, 1998 BSD
