| UGEN(4) | Device Drivers Manual | UGEN(4) | 
ugen —
ugen* at uhub? flags N
ugen* at uhub? vendor V product P flags 1
ugenif* at uhub? vendor V product P configuration C interface
  I
ugenif* at uhub? vendor V product P configuration C interface I
  flags 1
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.
The ‘ugenif’ form of attachment can be used to
    “steal” only one interface from some device for use by the
    ugen driver. Most likely you want to explicitly
    specify at least vendor, product and interface with this form, as otherwise
    the ugen driver would capture all of your
    usb devices. If “flags 1” is
    specified, the ‘ugenif’ form will match at the lowest
    priority, thus allowing it to match only otherwise unclaimed interfaces.
    NOTE: You have to be extremely careful, when using this
    form, as the attached ugen driver has access to all
    of the device and can easily interfere with the driver(s) used for the other
    interface(s).
As an example of this second form of attachment there are various
    debugging boards available based on some FTDI chip, where one interface is
    used for JTAG debugging and the other is used as a serial interface. In this
    case you want to attach the ugen driver to interface
    0 of this particular board identified by vendor and
    product while letting
    uftdi(4) together with
    ucom(4) to attach at interface
    1.
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)USB_SET_TIMEOUT
    (int)The control endpoint (endpoint 0) handles the following ioctl(2) calls:
USB_GET_CONFIG
    (int)USB_SET_CONFIG
    (int)This operation can only be performed when the control endpoint is the sole open endpoint.
USB_GET_ALTINTERFACE
    (struct usb_alt_interface)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)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)uai_alt_no field.USB_GET_DEVICE_DESC
    (usb_device_descriptor_t)USB_GET_CONFIG_DESC
    (struct usb_config_desc)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)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)
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)
struct usb_full_desc {
	int	ufd_config_index;
	u_int	ufd_size;
	u_char	*ufd_data;
};
    
    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)
struct usb_string_desc {
	int	usd_string_index;
	int	usd_language_id;
	usb_string_descriptor_t usd_desc;
};
    
    USB_DO_REQUESTdata. 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 */
};
    
    USB_GET_DEVICEINFO
    (struct usb_device_info)Bulk endpoints handle the following ioctl(2) calls:
USB_SET_BULK_RA
    (int)USB_SET_BULK_RA_OPT
      ioctl(2) call.USB_SET_BULK_WB
    (int)USB_SET_BULK_WB_OPT
      ioctl(2) call.USB_SET_BULK_RA_OPT
    (struct usb_bulk_ra_wb_opt)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)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.
ugen driver appeared in NetBSD
  1.4.
| March 25, 2024 | NetBSD 10.1 |