NAME
ugen —
USB generic device
support
SYNOPSIS
ugen* at uhub? flags N
DESCRIPTION
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.
Normally the
ugen driver is used when no other driver attaches
to a device. If “flags 1” is specified, the
ugen
will instead attach with a very high priority and always be used. Together
with the
vendor and
product locators this
can be used to force the
ugen driver to be used for a
certain device.
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 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 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 requests and may respond with
an answer to such requests. Control requests are issued by
ioctl(2) calls.
The bulk transfer mode can be in or out depending on the endpoint. To perform IO
on a bulk endpoint
read(2) and
write(2) should be used. All IO
operations on a bulk endpoint are normally unbuffered. The
USB_SET_BULK_RA
and
USB_SET_BULK_WB
ioctl(2) calls enable read-ahead
and write-behind buffering, respectively. This buffering supports fixed-sized
USB transfers and is intended for devices with regular and continuing data
transfers. When read-ahead or write-behind are enabled, the file descriptor
may be set to use non-blocking IO.
When in a read-ahead/writeback mode,
select(2) for read and write
operates normally, returning true if there is data in the read buffer and
space in the write buffer, respectively. When not,
select(2) always returns true,
because there is no way to predict how the device will respond to a read or
write request.
The interrupt transfer mode can be in or out depending on the endpoint. To
perform IO 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
config_index
is ignored in
this call.
struct usb_alt_interface {
int uai_config_index;
int uai_interface_index;
int uai_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
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
.
struct usb_config_desc {
int ucd_config_index;
usb_config_descriptor_t ucd_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 uid_config_index;
int uid_interface_index;
int uid_alt_index;
usb_interface_descriptor_t uid_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
endpoint index.
struct usb_endpoint_desc {
int ued_config_index;
int ued_interface_index;
int ued_alt_index;
int ued_endpoint_index;
usb_endpoint_descriptor_t ued_desc;
};
USB_GET_FULL_DESC
(struct usb_full_desc)
- Return all the descriptors for the given configuration.
struct usb_full_desc {
int ufd_config_index;
u_int ufd_size;
u_char *ufd_data;
};
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.
struct usb_string_desc {
int usd_string_index;
int usd_language_id;
usb_string_descriptor_t usd_desc;
};
USB_DO_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
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 the
ucr_actlen
field will contain the actual size on
completion.
struct usb_ctl_request {
int ucr_addr;
usb_device_request_t ucr_request;
void *ucr_data;
int ucr_flags;
#define USBD_SHORT_XFER_OK 0x04 /* allow short reads */
int ucr_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.
Bulk endpoints handle the following
ioctl(2) calls:
USB_SET_BULK_RA
(int)
- Enable or disable bulk read-ahead. When enabled, the driver
will begin to read data from the device into a buffer, and will perform
reads from the device whenever there is room in the buffer. The
read(2) call will read data
from this buffer, blocking if necessary until there is enough data to read
the length of data requested. The buffer size and the read request length
can be set by the
USB_SET_BULK_RA_OPT
ioctl(2) call.
USB_SET_BULK_WB
(int)
- Enable or disable bulk write-behind. When enabled, the
driver will buffer data from the
write(2) call before writing
it to the device, enabling the
write(2) call to return
immediately. write(2) will
block if there is not enough room in the buffer for all the data. The
buffer size and the write request length can be set by the
USB_SET_BULK_WB_OPT
ioctl(2) call.
USB_SET_BULK_RA_OPT
(struct usb_bulk_ra_wb_opt)
- Set the size of the buffer and the length of the read
requests used by the driver when bulk read-ahead is enabled. The changes
do not take effect until the next time bulk read-ahead is enabled. Read
requests are made for the length specified, and the host controller driver
(i.e., ehci(4),
ohci(4), and
uhci(4)) will perform as many
bus transfers as required. If transfers from the device should be smaller
than the maximum length,
ra_wb_request_size
must
be set to the required length.
struct usb_bulk_ra_wb_opt {
u_int ra_wb_buffer_size;
u_int ra_wb_request_size;
};
USB_SET_BULK_WB_OPT
(struct usb_bulk_ra_wb_opt)
- Set the size of the buffer and the length of the write
requests used by the driver when bulk write-behind is enabled. The changes
do not take effect until the next time bulk write-behind is enabled.
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 use 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 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 ALSO
usb(4)
HISTORY
The
ugen driver appeared in
NetBSD
1.4.