ugen —
USB
generic device support
| ugen |
is integrated into the usb(4) kernel
module. |
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 communicate 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 determine which endpoint the device accesses, and
the rest of the bits determine 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 which endpoints exist, there are a series of
ioctl(2) operations on the control endpoint that
return 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 a request and may respond with
an answer to such a request. Control requests 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 be in or out depending on the endpoint. To
perform I/O on an interrupt endpoint
read(2) and
write(2) should be used. A moderate amount of
buffering 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 uai_config_index is
ignored in this call.
-
USB_SET_ALTINTERFACE
(struct usb_alt_interface)
- Set the alternative setting to the given number in the
interface with the given index. The
uai_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
uai_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.
-
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.
-
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
endpoint index.
-
USB_GET_FULL_DESC
(struct usb_full_desc)
- Return all the descriptors for the given configuration.
The ufd_data field should point to a memory
area of the size given in the ufd_size
field. The proper size can be determined by first issuing 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.
-
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
ucr_data. The size of the transferred
data is determined from the ucr_request.
The ucr_addr field is ignored in this
call. The ucr_flags field can be used to
flag that the request is allowed to be shorter than the requested size,
and ucr_actlen will contain the actual
size on completion.
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 presented by the device. The
number is the respective number of the entity as found in its descriptor.
Enumeration of descriptors uses the index, getting and setting typically uses
numbers.
Example: all endpoints (except the control endpoint) for the current
configuration 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 be set to
USB_CURRENT_CONFIG_INDEX and
alt_index should be set to
USB_CURRENT_ALT_INDEX.
The following variables are available as both
sysctl(8) variables and
loader(8) tunables:
- hw.usb.ugen.debug
- Debug output level, where 0 is debugging disabled and
larger values increase debug message verbosity. Default is 0.
-
/dev/ugenN.E
- Endpoint E of device
N.
usb(4)
The
ugen driver appeared in
NetBSD
1.4.