1. NAME▲

struct_usb_gadget - represents a usb slave device

2. SYNOPSIS ▲



 
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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;
};

3. 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

4. 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 thatAqs 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).

5. AUTHOR ▲

David Brownell <>
    Author.

6. COPYRIGHT ▲