s390/cio/isc.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Functions for registration of I/O interruption subclasses on s390.
0004  *
0005  * Copyright IBM Corp. 2008
0006  * Authors: Sebastian Ott <sebott@linux.vnet.ibm.com>
0007  */
0008
0009 #include <linux/spinlock.h>
0010 #include <linux/module.h>
0011 #include <asm/isc.h>
0012
0013 static unsigned int isc_refs[MAX_ISC + 1];
0014 static DEFINE_SPINLOCK(isc_ref_lock);
0015
0016
0017 /**
0018  * isc_register - register an I/O interruption subclass.
0019  * @isc: I/O interruption subclass to register
0020  *
0021  * The number of users for @isc is increased. If this is the first user to
0022  * register @isc, the corresponding I/O interruption subclass mask is enabled.
0023  *
0024  * Context:
0025  *   This function must not be called in interrupt context.
0026  */
0027 void isc_register(unsigned int isc)
0028 {
0029     if (isc > MAX_ISC) {
0030         WARN_ON(1);
0031         return;
0032     }
0033
0034     spin_lock(&isc_ref_lock);
0035     if (isc_refs[isc] == 0)
0036         ctl_set_bit(6, 31 - isc);
0037     isc_refs[isc]++;
0038     spin_unlock(&isc_ref_lock);
0039 }
0040 EXPORT_SYMBOL_GPL(isc_register);
0041
0042 /**
0043  * isc_unregister - unregister an I/O interruption subclass.
0044  * @isc: I/O interruption subclass to unregister
0045  *
0046  * The number of users for @isc is decreased. If this is the last user to
0047  * unregister @isc, the corresponding I/O interruption subclass mask is
0048  * disabled.
0049  * Note: This function must not be called if isc_register() hasn't been called
0050  * before by the driver for @isc.
0051  *
0052  * Context:
0053  *   This function must not be called in interrupt context.
0054  */
0055 void isc_unregister(unsigned int isc)
0056 {
0057     spin_lock(&isc_ref_lock);
0058     /* check for misuse */
0059     if (isc > MAX_ISC || isc_refs[isc] == 0) {
0060         WARN_ON(1);
0061         goto out_unlock;
0062     }
0063     if (isc_refs[isc] == 1)
0064         ctl_clear_bit(6, 31 - isc);
0065     isc_refs[isc]--;
0066 out_unlock:
0067     spin_unlock(&isc_ref_lock);
0068 }
0069 EXPORT_SYMBOL_GPL(isc_unregister);