1. 根目录:
2. include
3. linux
4. usb
5. otg.h

/* USB OTG (On The Go) defines */
/*
 *
 * These APIs may be used between USB controllers.  USB device drivers
 * (for either host or peripheral roles) don't use these calls; they
 * continue to use just usb_device and usb_gadget.
 */

#ifndef __LINUX_USB_OTG_H
#define __LINUX_USB_OTG_H

#include <linux/usb/phy.h>

struct usb_otg {
	u8			default_a;

	struct usb_phy		*phy;
	struct usb_bus		*host;
	struct usb_gadget	*gadget;

	/* bind/unbind the host controller */
	int	(*set_host)(struct usb_otg *otg, struct usb_bus *host);

	/* bind/unbind the peripheral controller */
	int	(*set_peripheral)(struct usb_otg *otg,
					struct usb_gadget *gadget);

	/* effective for A-peripheral, ignored for B devices */
	int	(*set_vbus)(struct usb_otg *otg, bool enabled);

	/* for B devices only:  start session with A-Host */
	int	(*start_srp)(struct usb_otg *otg);

	/* start or continue HNP role switch */
	int	(*start_hnp)(struct usb_otg *otg);

};

extern const char *usb_otg_state_string(enum usb_otg_state state);

/* Context: can sleep */
static inline int
otg_start_hnp(struct usb_otg *otg)
{
	if (otg && otg->start_hnp)
		return otg->start_hnp(otg);

	return -ENOTSUPP;
}

/* Context: can sleep */
static inline int
otg_set_vbus(struct usb_otg *otg, bool enabled)
{
	if (otg && otg->set_vbus)
		return otg->set_vbus(otg, enabled);

	return -ENOTSUPP;
}

/* for HCDs */
static inline int
otg_set_host(struct usb_otg *otg, struct usb_bus *host)
{
	if (otg && otg->set_host)
		return otg->set_host(otg, host);

	return -ENOTSUPP;
}

/* for usb peripheral controller drivers */

/* Context: can sleep */
static inline int
otg_set_peripheral(struct usb_otg *otg, struct usb_gadget *periph)
{
	if (otg && otg->set_peripheral)
		return otg->set_peripheral(otg, periph);

	return -ENOTSUPP;
}

static inline int
otg_start_srp(struct usb_otg *otg)
{
	if (otg && otg->start_srp)
		return otg->start_srp(otg);

	return -ENOTSUPP;
}

/* for OTG controller drivers (and maybe other stuff) */
extern int usb_bus_start_enum(struct usb_bus *bus, unsigned port_num);

enum usb_dr_mode {
	USB_DR_MODE_UNKNOWN,
	USB_DR_MODE_HOST,
	USB_DR_MODE_PERIPHERAL,
	USB_DR_MODE_OTG,
};

#endif /* __LINUX_USB_OTG_H */