struct usb_gadget_dr(9)
NAME
struct_usb_gadget_driver - driver for usb 'slave' devices
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 *);
struct device_driver driver;
};
MEMBERS
- function
- String describing the gadgetīs 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 arenīt 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 USB byte 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. Some devices canīt detect disconnect, so this might not be called except as part of controller shutdown. - suspend
- Invoked on USB suspend. May be called in_interrupt.
- resume
- Invoked on USB resume. May be called in_interrupt.
- driver
- Driver model state for this driver.
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.
If gadget->is_otg is true, the gadget driver must provide an OTG
descriptor during enumeration, or else fail the bind call. In such
cases, no USB traffic may flow until both bind returns without having
called usb_gadget_disconnect, and the USB host stack has initialized.
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 shouldnīt need change
to run on top of different usb controllers. Itīll 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 driverīs 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 driverīs 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 canīt do that any longer; or an error state might be
cleared, to make the device behave identically whether or not power is
maintained.
AUTHOR
- David Brownell <dbrownell@users.sourceforge.net>
- Author.