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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

June 2024 Kernel Hackers Manual 3.10