https://source.codeaurora.org/external/gigabyte/ag-gb-dsds-7227/plain/kernel/drivers/usb/otg/otg.c
/*
* otg.c -- USB OTG utility code
*
* Copyright (C) 2004 Texas Instruments
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/usb/otg.h>
static struct otg_transceiver *xceiv;
/**
* otg_get_transceiver - find the (single) OTG transceiver
*
* Returns the transceiver driver, after getting a refcount to it; or
* null if there is no such transceiver. The caller is responsible for
* calling otg_put_transceiver() to release that count.
*
* For use by USB host and peripheral drivers.
*/
struct otg_transceiver *otg_get_transceiver(void)
{
if (xceiv)
get_device(xceiv->dev);
return xceiv;
}
EXPORT_SYMBOL(otg_get_transceiver);
/**
* otg_put_transceiver - release the (single) OTG transceiver
* @x: the transceiver returned by otg_get_transceiver()
*
* Releases a refcount the caller received from otg_get_transceiver().
*
* For use by USB host and peripheral drivers.
*/
void otg_put_transceiver(struct otg_transceiver *x)
{
if (x)
put_device(x->dev);
}
EXPORT_SYMBOL(otg_put_transceiver);
/**
* otg_set_transceiver - declare the (single) OTG transceiver
* @x: the USB OTG transceiver to be used; or NULL
*
* This call is exclusively for use by transceiver drivers, which
* coordinate the activities of drivers for host and peripheral
* controllers, and in some cases for VBUS current regulation.
*/
int otg_set_transceiver(struct otg_transceiver *x)
{
if (xceiv && x)
return -EBUSY;
xceiv = x;
return 0;
}
EXPORT_SYMBOL(otg_set_transceiver);
int otg_send_event(enum usb_otg_event event)
{
struct otg_transceiver *otg = otg_get_transceiver();
int ret = -ENOTSUPP;
if (otg && otg->send_event)
ret = otg->send_event(otg, event);
if (otg)
otg_put_transceiver(otg);
return ret;
}
EXPORT_SYMBOL(otg_send_event);