drivers/usb/otg/otg.c

   1 /*
   2  * otg.c -- USB OTG utility code
   3  *
   4  * Copyright (C) 2004 Texas Instruments
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  */
  11
  12 #include <linux/kernel.h>
  13 #include <linux/device.h>
  14
  15 #include <linux/usb/otg.h>
  16
  17 static struct otg_transceiver *xceiv;
  18
  19 /**
  20  * otg_get_transceiver - find the (single) OTG transceiver
  21  *
  22  * Returns the transceiver driver, after getting a refcount to it; or
  23  * null if there is no such transceiver.  The caller is responsible for
  24  * calling otg_put_transceiver() to release that count.
  25  *
  26  * For use by USB host and peripheral drivers.
  27  */
  28 struct otg_transceiver *otg_get_transceiver(void)
  29 {
  30         if (xceiv)
  31                 get_device(xceiv->dev);
  32         return xceiv;
  33 }
  34 EXPORT_SYMBOL(otg_get_transceiver);
  35
  36 /**
  37  * otg_put_transceiver - release the (single) OTG transceiver
  38  * @x: the transceiver returned by otg_get_transceiver()
  39  *
  40  * Releases a refcount the caller received from otg_get_transceiver().
  41  *
  42  * For use by USB host and peripheral drivers.
  43  */
  44 void otg_put_transceiver(struct otg_transceiver *x)
  45 {
  46         put_device(x->dev);
  47 }
  48 EXPORT_SYMBOL(otg_put_transceiver);
  49
  50 /**
  51  * otg_set_transceiver - declare the (single) OTG transceiver
  52  * @x: the USB OTG transceiver to be used; or NULL
  53  *
  54  * This call is exclusively for use by transceiver drivers, which
  55  * coordinate the activities of drivers for host and peripheral
  56  * controllers, and in some cases for VBUS current regulation.
  57  */
  58 int otg_set_transceiver(struct otg_transceiver *x)
  59 {
  60         if (xceiv && x)
  61                 return -EBUSY;
  62         xceiv = x;
  63         return 0;
  64 }
  65 EXPORT_SYMBOL(otg_set_transceiver);