drivers/s390/cio/isc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Functions for registration of I/O interruption subclasses on s390.
   4  *
   5  * Copyright IBM Corp. 2008
   6  * Authors: Sebastian Ott <sebott@linux.vnet.ibm.com>
   7  */
   8
   9 #include <linux/spinlock.h>
  10 #include <linux/module.h>
  11 #include <asm/isc.h>
  12
  13 static unsigned int isc_refs[MAX_ISC + 1];
  14 static DEFINE_SPINLOCK(isc_ref_lock);
  15
  16
  17 /**
  18  * isc_register - register an I/O interruption subclass.
  19  * @isc: I/O interruption subclass to register
  20  *
  21  * The number of users for @isc is increased. If this is the first user to
  22  * register @isc, the corresponding I/O interruption subclass mask is enabled.
  23  *
  24  * Context:
  25  *   This function must not be called in interrupt context.
  26  */
  27 void isc_register(unsigned int isc)
  28 {
  29         if (isc > MAX_ISC) {
  30                 WARN_ON(1);
  31                 return;
  32         }
  33
  34         spin_lock(&isc_ref_lock);
  35         if (isc_refs[isc] == 0)
  36                 ctl_set_bit(6, 31 - isc);
  37         isc_refs[isc]++;
  38         spin_unlock(&isc_ref_lock);
  39 }
  40 EXPORT_SYMBOL_GPL(isc_register);
  41
  42 /**
  43  * isc_unregister - unregister an I/O interruption subclass.
  44  * @isc: I/O interruption subclass to unregister
  45  *
  46  * The number of users for @isc is decreased. If this is the last user to
  47  * unregister @isc, the corresponding I/O interruption subclass mask is
  48  * disabled.
  49  * Note: This function must not be called if isc_register() hasn't been called
  50  * before by the driver for @isc.
  51  *
  52  * Context:
  53  *   This function must not be called in interrupt context.
  54  */
  55 void isc_unregister(unsigned int isc)
  56 {
  57         spin_lock(&isc_ref_lock);
  58         /* check for misuse */
  59         if (isc > MAX_ISC || isc_refs[isc] == 0) {
  60                 WARN_ON(1);
  61                 goto out_unlock;
  62         }
  63         if (isc_refs[isc] == 1)
  64                 ctl_clear_bit(6, 31 - isc);
  65         isc_refs[isc]--;
  66 out_unlock:
  67         spin_unlock(&isc_ref_lock);
  68 }
  69 EXPORT_SYMBOL_GPL(isc_unregister);