USB_GADGET_DRIVER

NAME

SYNOPSIS

struct usb_gadget_driver {
  char * function;
  enum usb_device_speed speed;
  int (* bind (struct usb_gadget *);
  void (* unbind (struct usb_gadget *);
  int (* setup (struct usb_gadget *,const struct usb_ctrlrequest *);
  void (* disconnect (struct usb_gadget *);
  void (* suspend (struct usb_gadget *);
  void (* resume (struct usb_gadget *);
};  

MEMBERS

function

String describing the gadget's function

speed

Highest speed the driver handles.

bind

Invoked when the driver is bound to a gadget, usually after registering the driver. At that point, ep0 is fully initialized, and ep_list holds the currently-available endpoints. Called in a context that permits sleeping.

unbind

Invoked when the driver is unbound from a gadget, usually from rmmod (after a disconnect is reported). Called in a context that permits sleeping.

setup

Invoked for ep0 control requests that aren't handled by the hardware level driver. Most calls must be handled by the gadget driver, including descriptor and configuration management. The 16 bit members of the setup data are in cpu order. Called in_interrupt; this may not sleep. Driver queues a response to ep0, or returns negative to stall.

disconnect

Invoked after all transfers have been stopped, when the host is disconnected. May be called in_interrupt; this may not sleep.

suspend

Invoked on USB suspend. May be called in_interrupt.

resume

Invoked on USB resume. May be called in_interrupt.

DESCRIPTION

Devices are disabled till a gadget driver successfully binds, which means the driver will handle setup requests needed to enumerate (and meet ``chapter 9'' requirements) then do some useful work.

Drivers use hardware-specific knowledge to configure the usb hardware. endpoint addressing is only one of several hardware characteristics that are in descriptors the ep0 implementation returns from setup calls.

Except for ep0 implementation, most driver code shouldn't need change to run on top of different usb controllers. It'll use endpoints set up by that ep0 implementation.

The usb controller driver handles a few standard usb requests. Those include set_address, and feature flags for devices, interfaces, and endpoints (the get_status, set_feature, and clear_feature requests).

Accordingly, the driver's setup callback must always implement all get_descriptor requests, returning at least a device descriptor and a configuration descriptor. Drivers must make sure the endpoint descriptors match any hardware constraints. Some hardware also constrains other descriptors. (The pxa250 allows only configurations 1, 2, or 3).

The driver's setup callback must also implement set_configuration, and should also implement set_interface, get_configuration, and get_interface. Setting a configuration (or interface) is where endpoints should be activated or (config 0) shut down.

(Note that only the default control endpoint is supported. Neither hosts nor devices generally support control traffic except to ep0.)

Most devices will ignore USB suspend/resume operations, and so will not provide those callbacks. However, some may need to change modes when the host is not longer directing those activities. For example, local controls (buttons, dials, etc) may need to be re-enabled since the (remote) host can't do that any longer.  

ABOUT THIS DOCUMENT

Permission is granted to copy, distribute, and/or modify this document under the terms of the GNU Free Documentation License, version 1.2, or any later version published by the Free Software Foundation; with the Invariant Sections being the "GNU Free Documentation License", no Front-Cover Texts, and no Back-Cover Texts.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Free Documentation License for more details.

Note that certain sections of this document are merged into Linux kernel source code. That content is the bulk of [XRef to CORE]> and [XRef to UTILS]>, where the "GNU Free Documentation License" is identified as an alternate licence for its documentation.

If you have comments on the formatting of this manpage, then please contact Michael Still (mikal@stillhq.com).

This documentation was generated with kernel version 2.5.73.

Index

NAME

SYNOPSIS

MEMBERS

DESCRIPTION

ABOUT THIS DOCUMENT