STRUCT 
USB_GADGET(9)					      Kernel Mode Gadget API					      STRUCT USB_GADGET(9)

NAME

       struct_usb_gadget - represents a usb slave device

SYNOPSIS

       struct usb_gadget {
	 const struct usb_gadget_ops * ops;
	 struct usb_ep * ep0;
	 struct list_head ep_list;
	 enum usb_device_speed speed;
	 enum usb_device_speed max_speed;
	 enum usb_device_state state;
	 unsigned sg_supported:1;
	 unsigned is_otg:1;
	 unsigned is_a_peripheral:1;
	 unsigned b_hnp_enable:1;
	 unsigned a_hnp_support:1;
	 unsigned a_alt_hnp_support:1;
	 const char * name;
	 struct device dev;
	 unsigned out_epnum;
	 unsigned in_epnum;
       };

MEMBERS

       ops
	   Function pointers used to access hardware-specific operations.

       ep0
	   Endpoint zero, used when reading or writing responses to driver setup requests

       ep_list
	   List of other endpoints supported by the device.

       speed
	   Speed of current connection to USB host.

       max_speed
	   Maximal speed the UDC can handle. UDC must support this and all slower speeds.

       state
	   the state we are now (attached, suspended, configured, etc)

       sg_supported
	   true if we can handle scatter-gather

       is_otg
	   True if the USB device port uses a Mini-AB jack, so that the gadget driver must provide a USB OTG descriptor.

       is_a_peripheral
	   False unless is_otg, the "A" end of a USB cable is in the Mini-AB jack, and HNP has been used to switch roles so that the "A" device
	   currently acts as A-Peripheral, not A-Host.

       b_hnp_enable
	   OTG device feature flag, indicating that the A-Host enabled HNP support.

       a_hnp_support
	   OTG device feature flag, indicating that the A-Host supports HNP at this port.

       a_alt_hnp_support
	   OTG device feature flag, indicating that the A-Host only supports HNP on a different root port.

       name
	   Identifies the controller hardware type. Used in diagnostics and sometimes configuration.

       dev
	   Driver model state for this abstract device.

       out_epnum
	   last used out ep number

       in_epnum
	   last used in ep number

DESCRIPTION

       Gadgets have a mostly-portable "gadget driver" implementing device functions, handling all usb configurations and interfaces. Gadget
       drivers talk to hardware-specific code indirectly, through ops vectors. That insulates the gadget driver from hardware details, and
       packages the hardware endpoints through generic i/o queues. The "usb_gadget" and "usb_ep" interfaces provide that insulation from the
       hardware.

       Except for the driver data, all fields in this structure are read-only to the gadget driver. That driver data is part of the "driver model"
       infrastructure in 2.6 (and later) kernels, and for earlier systems is grouped in a similar structure that's not known to the rest of the
       kernel.

       Values of the three OTG device feature flags are updated before the setup call corresponding to USB_REQ_SET_CONFIGURATION, and before
       driver suspend calls. They are valid only when is_otg, and when the device is acting as a B-Peripheral (so is_a_peripheral is false).

AUTHOR

       David Brownell <dbrownell@users.sourceforge.net>
	   Author.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014						      STRUCT USB_GADGET(9)