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
  12 static unsigned int isc_refs[MAX_ISC + 1];
  13 static 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  */
  26 void 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 }
  39 EXPORT_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  */
  54 void 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]--;
  65 out_unlock:
  66         spin_unlock(&isc_ref_lock);
  67 }
  68 EXPORT_SYMBOL_GPL(isc_unregister);