STRUCT USB_GADGET(9)

NAME
struct_usb_gadget - represents a usb slave device

SYNOPSIS

struct usb_gadget {
  struct work_struct work;
  struct usb_udc * udc;
  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;
  const char * name;
  struct device dev;
  unsigned out_epnum;
  unsigned in_epnum;
  unsigned mA;
  struct usb_otg_caps * otg_caps;
  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;
  unsigned hnp_polling_support:1;
  unsigned host_request_flag:1;
  unsigned quirk_ep_out_aligned_size:1;
  unsigned quirk_avoids_skb_reserve:1;
  unsigned is_selfpowered:1;
  unsigned deactivated:1;
  unsigned connected:1;
};

MEMBERS

work
    (internal use) Workqueue to be used for sysfs_notify

udc
    struct usb_udc pointer for this gadget

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)

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

mA
    last set mA value

otg_caps
    OTG capabilities of this gadget.

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.

hnp_polling_support
    OTG device feature flag, indicating if the OTG device in peripheral mode can support HNP polling.

host_request_flag
    OTG device feature flag, indicating if A-Peripheral or B-Peripheral wants to take host role.

quirk_ep_out_aligned_size
    epout requires buffer size to be aligned to MaxPacketSize.

quirk_avoids_skb_reserve
    udc/platform wants to avoid skb_reserve in u_ether.c to improve performance.

is_selfpowered
    if the gadget is self-powered.

deactivated
    True if gadget is deactivated - in deactivated state it cannot be connected.

connected
    True if gadget is connected.

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.

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