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     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

     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

     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:

             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

     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.

             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 (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.

             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

     USB_GET_DEVICEINFO (struct usb_device_info)
             Get an information summary for the device.  This call will not issue any USB

     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


     The following variables are available as both sysctl(8) variables and loader(8) tunables:

             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.




     The ugen driver appeared in NetBSD 1.4.