LXR linux/drivers/s390/cio/isc.c

   1/*
   2 * Functions for registration of I/O interruption subclasses on s390.
   3 *
   4 * Copyright IBM Corp. 2008
   5 * Authors: Sebastian Ott <sebott@linux.vnet.ibm.com>
   6 */
   7
   8#include <linux/spinlock.h>
   9#include <linux/module.h>
  10#include <asm/isc.h>
  11
  12static unsigned int isc_refs[MAX_ISC + 1];
  13static DEFINE_SPINLOCK(isc_ref_lock);
  14
  15
  16/**
  17 * isc_register - register an I/O interruption subclass.
  18 * @isc: I/O interruption subclass to register
  19 *
  20 * The number of users for @isc is increased. If this is the first user to
  21 * register @isc, the corresponding I/O interruption subclass mask is enabled.
  22 *
  23 * Context:
  24 *   This function must not be called in interrupt context.
  25 */
  26void isc_register(unsigned int isc)
  27{
  28        if (isc > MAX_ISC) {
  29                WARN_ON(1);
  30                return;
  31        }
  32
  33        spin_lock(&isc_ref_lock);
  34        if (isc_refs[isc] == 0)
  35                ctl_set_bit(6, 31 - isc);
  36        isc_refs[isc]++;
  37        spin_unlock(&isc_ref_lock);
  38}
  39EXPORT_SYMBOL_GPL(isc_register);
  40
  41/**
  42 * isc_unregister - unregister an I/O interruption subclass.
  43 * @isc: I/O interruption subclass to unregister
  44 *
  45 * The number of users for @isc is decreased. If this is the last user to
  46 * unregister @isc, the corresponding I/O interruption subclass mask is
  47 * disabled.
  48 * Note: This function must not be called if isc_register() hasn't been called
  49 * before by the driver for @isc.
  50 *
  51 * Context:
  52 *   This function must not be called in interrupt context.
  53 */
  54void isc_unregister(unsigned int isc)
  55{
  56        spin_lock(&isc_ref_lock);
  57        /* check for misuse */
  58        if (isc > MAX_ISC || isc_refs[isc] == 0) {
  59                WARN_ON(1);
  60                goto out_unlock;
  61        }
  62        if (isc_refs[isc] == 1)
  63                ctl_clear_bit(6, 31 - isc);
  64        isc_refs[isc]--;
  65out_unlock:
  66        spin_unlock(&isc_ref_lock);
  67}
  68EXPORT_SYMBOL_GPL(isc_unregister);
  69