/*
   * Functions for registration of I/O interruption subclasses on s390.
   *
   * Copyright IBM Corp. 2008
   * Authors: Sebastian Ott <sebott@linux.vnet.ibm.com>
   */
  
  #include <linux/spinlock.h>
  #include <linux/module.h>
  #include <asm/isc.h>
  
  static unsigned int isc_refs[MAX_ISC + 1];
  static DEFINE_SPINLOCK(isc_ref_lock);
  
  
  /**
   * isc_register - register an I/O interruption subclass.
   * @isc: I/O interruption subclass to register
   *
   * The number of users for @isc is increased. If this is the first user to
   * register @isc, the corresponding I/O interruption subclass mask is enabled.
   *
   * Context:
   *   This function must not be called in interrupt context.
   */
  void isc_register(unsigned int isc)
  {
  	if (isc > MAX_ISC) {
  		WARN_ON(1);
  		return;
  	}
  
  	spin_lock(&isc_ref_lock);
  	if (isc_refs[isc] == 0)
  		ctl_set_bit(6, 31 - isc);
  	isc_refs[isc]++;
  	spin_unlock(&isc_ref_lock);
  }
  EXPORT_SYMBOL_GPL(isc_register);
  
  /**
   * isc_unregister - unregister an I/O interruption subclass.
   * @isc: I/O interruption subclass to unregister
   *
   * The number of users for @isc is decreased. If this is the last user to
   * unregister @isc, the corresponding I/O interruption subclass mask is
   * disabled.
   * Note: This function must not be called if isc_register() hasn't been called
   * before by the driver for @isc.
   *
   * Context:
   *   This function must not be called in interrupt context.
   */
  void isc_unregister(unsigned int isc)
  {
  	spin_lock(&isc_ref_lock);
  	/* check for misuse */
  	if (isc > MAX_ISC || isc_refs[isc] == 0) {
  		WARN_ON(1);
  		goto out_unlock;
  	}
  	if (isc_refs[isc] == 1)
  		ctl_clear_bit(6, 31 - isc);
  	isc_refs[isc]--;
  out_unlock:
  	spin_unlock(&isc_ref_lock);
  }
  EXPORT_SYMBOL_GPL(isc_unregister);