MirBSD manpage: ugen(4)

UGEN(4)                    BSD Programmer's Manual                     UGEN(4)


     ugen - USB generic device support


     ugen* at uhub? port ? configuration ?


     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 dev-
     ice 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 what endpoints exist there are a series of ioctl(2) opera-
     tions available for 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. 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 only be in. To perform input from an in-
     terrupt endpoint read(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 er-
     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

     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 opera-
             tion 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.

             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

             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

             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

             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 end-
             point 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 in-

             struct usb_string_desc {
                     int     usd_string_index;
                     int     usd_language_id;
                     usb_string_descriptor_t usd_desc;

             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.

             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 is-
             sue any USB transactions.

     Note that there are two different ways of addressing configurations, in-
     terfaces, 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 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-*(GtbNumEndpoints. The
     config_index should set to USB_CURRENT_CONFIG_INDEX and alt_index should
     be set to USB_CURRENT_ALT_INDEX.


     /dev/ugenN.EE                     Endpoint EE of device N.


     intro(4), uhub(4), usb(4)


     The ugen driver appeared in OpenBSD 2.6.


     The driver is not yet finished; there is no access to isochronous end-

MirBSD #10-current            December 15, 2003                              2

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