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[linux-2.6.9-moxart.git] / arch / x86_64 / kernel / irq.c

/*
 *      linux/arch/x86_64/kernel/irq.c
 *
 *      Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
 *
 * This file contains the code used by various IRQ handling routines:
 * asking for different IRQ's should be done through these routines
 * instead of just grabbing them. Thus setups with different IRQ numbers
 * shouldn't result in any weird surprises, and installing new handlers
 * should be easier.
 */

/*
 * (mostly architecture independent, will move to kernel/irq.c in 2.5.)
 *
 * IRQs are in fact implemented a bit like signal handlers for the kernel.
 * Naturally it's not a 1:1 relation, but there are similarities.
 */

#include <linux/config.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/kernel_stat.h>
#include <linux/irq.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>

#include <asm/atomic.h>
#include <asm/io.h>
#include <asm/smp.h>
#include <asm/system.h>
#include <asm/bitops.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/delay.h>
#include <asm/desc.h>
#include <asm/irq.h>



/*
 * Linux has a controller-independent x86 interrupt architecture.
 * every controller has a 'controller-template', that is used
 * by the main code to do the right thing. Each driver-visible
 * interrupt source is transparently wired to the appropriate
 * controller. Thus drivers need not be aware of the
 * interrupt-controller.
 *
 * Various interrupt controllers we handle: 8259 PIC, SMP IO-APIC,
 * PIIX4's internal 8259 PIC and SGI's Visual Workstation Cobalt (IO-)APIC.
 * (IO-APICs assumed to be messaging to Pentium local-APICs)
 *
 * the code is designed to be easily extended with new/different
 * interrupt controllers, without having to do assembly magic.
 */

/*
 * Controller mappings for all interrupt sources:
 */
irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
        [0 ... NR_IRQS-1] = {
                .handler = &no_irq_type,
                .lock = SPIN_LOCK_UNLOCKED
        }
};

static void register_irq_proc (unsigned int irq);

/*
 * Special irq handlers.
 */

irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs) { return IRQ_NONE; }

/*
 * Generic no controller code
 */

static void enable_none(unsigned int irq) { }
static unsigned int startup_none(unsigned int irq) { return 0; }
static void disable_none(unsigned int irq) { }
static void ack_none(unsigned int irq)
{
/*
 * 'what should we do if we get a hw irq event on an illegal vector'.
 * each architecture has to answer this themselves, it doesn't deserve
 * a generic callback i think.
 */
#ifdef CONFIG_X86
        printk("unexpected IRQ trap at vector %02x\n", irq);
#ifdef CONFIG_X86_LOCAL_APIC
        /*
         * Currently unexpected vectors happen only on SMP and APIC.
         * We _must_ ack these because every local APIC has only N
         * irq slots per priority level, and a 'hanging, unacked' IRQ
         * holds up an irq slot - in excessive cases (when multiple
         * unexpected vectors occur) that might lock up the APIC
         * completely.
         */
        ack_APIC_irq();
#endif
#endif
}

/* startup is the same as "enable", shutdown is same as "disable" */
#define shutdown_none   disable_none
#define end_none        enable_none

struct hw_interrupt_type no_irq_type = {
        "none",
        startup_none,
        shutdown_none,
        enable_none,
        disable_none,
        ack_none,
        end_none
};

atomic_t irq_err_count;
#ifdef CONFIG_X86_IO_APIC
#ifdef APIC_MISMATCH_DEBUG
atomic_t irq_mis_count;
#endif
#endif

/*
 * Generic, controller-independent functions:
 */

int show_interrupts(struct seq_file *p, void *v)
{
        int i = *(loff_t *) v, j;
        struct irqaction * action;
        unsigned long flags;

        if (i == 0) {
                seq_printf(p, "           ");
                for (j=0; j<NR_CPUS; j++)
                        if (cpu_online(j))
                                seq_printf(p, "CPU%d       ",j);
                seq_putc(p, '\n');
        }

        if (i < NR_IRQS) {
                spin_lock_irqsave(&irq_desc[i].lock, flags);
                action = irq_desc[i].action;
                if (!action) 
                        goto skip;
                seq_printf(p, "%3d: ",i);
#ifndef CONFIG_SMP
                seq_printf(p, "%10u ", kstat_irqs(i));
#else
                for (j=0; j<NR_CPUS; j++)
                        if (cpu_online(j))
                        seq_printf(p, "%10u ",
                                kstat_cpu(j).irqs[i]);
#endif
                seq_printf(p, " %14s", irq_desc[i].handler->typename);

                seq_printf(p, "  %s", action->name);
                for (action=action->next; action; action = action->next)
                        seq_printf(p, ", %s", action->name);
                seq_putc(p, '\n');
skip:
                spin_unlock_irqrestore(&irq_desc[i].lock, flags);
        } else if (i == NR_IRQS) {
                seq_printf(p, "NMI: ");
                for (j = 0; j < NR_CPUS; j++)
                        if (cpu_online(j))
                                seq_printf(p, "%10u ", cpu_pda[j].__nmi_count);
                seq_putc(p, '\n');
#ifdef CONFIG_X86_LOCAL_APIC
                seq_printf(p, "LOC: ");
                for (j = 0; j < NR_CPUS; j++)
                        if (cpu_online(j))
                                seq_printf(p, "%10u ", cpu_pda[j].apic_timer_irqs);
                seq_putc(p, '\n');
#endif
                seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
#ifdef CONFIG_X86_IO_APIC
#ifdef APIC_MISMATCH_DEBUG
                seq_printf(p, "MIS: %10u\n", atomic_read(&irq_mis_count));
#endif
#endif
        }
        return 0;
}

#ifdef CONFIG_SMP
inline void synchronize_irq(unsigned int irq)
{
        while (irq_desc[irq].status & IRQ_INPROGRESS)
                cpu_relax();
}
#endif

/*
 * This should really return information about whether
 * we should do bottom half handling etc. Right now we
 * end up _always_ checking the bottom half, which is a
 * waste of time and is not what some drivers would
 * prefer.
 */
int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
{
        int status = 1; /* Force the "do bottom halves" bit */
        int ret;

        if (!(action->flags & SA_INTERRUPT))
                local_irq_enable();

        do {
                ret = action->handler(irq, action->dev_id, regs);
                if (ret == IRQ_HANDLED)
                        status |= action->flags;
                action = action->next;
        } while (action);
        if (status & SA_SAMPLE_RANDOM)
                add_interrupt_randomness(irq);
        local_irq_disable();

        return status;
}

/*
 * Generic enable/disable code: this just calls
 * down into the PIC-specific version for the actual
 * hardware disable after having gotten the irq
 * controller lock. 
 */
 
/**
 *      disable_irq_nosync - disable an irq without waiting
 *      @irq: Interrupt to disable
 *
 *      Disable the selected interrupt line.  Disables and Enables are
 *      nested.
 *      Unlike disable_irq(), this function does not ensure existing
 *      instances of the IRQ handler have completed before returning.
 *
 *      This function must not be called from IRQ context.
 */
 
inline void disable_irq_nosync(unsigned int irq)
{
        irq_desc_t *desc = irq_desc + irq;
        unsigned long flags;

        spin_lock_irqsave(&desc->lock, flags);
        if (!desc->depth++) {
                desc->status |= IRQ_DISABLED;
                desc->handler->disable(irq);
        }
        spin_unlock_irqrestore(&desc->lock, flags);
}

/**
 *      disable_irq - disable an irq and wait for completion
 *      @irq: Interrupt to disable
 *
 *      Disable the selected interrupt line.  Enables and Disables are
 *      nested.
 *      This function waits for any pending IRQ handlers for this interrupt
 *      to complete before returning. If you use this function while
 *      holding a resource the IRQ handler may need you will deadlock.
 *
 *      This function may be called - with care - from IRQ context.
 */
 
void disable_irq(unsigned int irq)
{
        disable_irq_nosync(irq);
        synchronize_irq(irq);
}

/**
 *      enable_irq - enable handling of an irq
 *      @irq: Interrupt to enable
 *
 *      Undoes the effect of one call to disable_irq().  If this
 *      matches the last disable, processing of interrupts on this
 *      IRQ line is re-enabled.
 *
 *      This function may be called from IRQ context.
 */
 
void enable_irq(unsigned int irq)
{
        irq_desc_t *desc = irq_desc + irq;
        unsigned long flags;

        spin_lock_irqsave(&desc->lock, flags);
        switch (desc->depth) {
        case 1: {
                unsigned int status = desc->status & ~IRQ_DISABLED;
                desc->status = status;
                if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
                        desc->status = status | IRQ_REPLAY;
                        hw_resend_irq(desc->handler,irq);
                }
                desc->handler->enable(irq);
                /* fall-through */
        }
        default:
                desc->depth--;
                break;
        case 0:
                printk("enable_irq(%u) unbalanced from %p\n", irq,
                       __builtin_return_address(0));
        }
        spin_unlock_irqrestore(&desc->lock, flags);
}

/*
 * do_IRQ handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
{       
        /* 
         * We ack quickly, we don't want the irq controller
         * thinking we're snobs just because some other CPU has
         * disabled global interrupts (we have already done the
         * INT_ACK cycles, it's too late to try to pretend to the
         * controller that we aren't taking the interrupt).
         *
         * 0 return value means that this irq is already being
         * handled by some other CPU. (or is disabled)
         */
        unsigned irq = regs->orig_rax & 0xff; /* high bits used in ret_from_ code  */
        int cpu = smp_processor_id();
        irq_desc_t *desc = irq_desc + irq;
        struct irqaction * action;
        unsigned int status;

        if (irq > 256) BUG();

        irq_enter(); 
        kstat_cpu(cpu).irqs[irq]++;
        spin_lock(&desc->lock);
        desc->handler->ack(irq);
        /*
           REPLAY is when Linux resends an IRQ that was dropped earlier
           WAITING is used by probe to mark irqs that are being tested
           */
        status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
        status |= IRQ_PENDING; /* we _want_ to handle it */

        /*
         * If the IRQ is disabled for whatever reason, we cannot
         * use the action we have.
         */
        action = NULL;
        if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
                action = desc->action;
                status &= ~IRQ_PENDING; /* we commit to handling */
                status |= IRQ_INPROGRESS; /* we are handling it */
        }
        desc->status = status;

        /*
         * If there is no IRQ handler or it was disabled, exit early.
           Since we set PENDING, if another processor is handling
           a different instance of this same irq, the other processor
           will take care of it.
         */
        if (unlikely(!action))
                goto out;

        /*
         * Edge triggered interrupts need to remember
         * pending events.
         * This applies to any hw interrupts that allow a second
         * instance of the same irq to arrive while we are in do_IRQ
         * or in the handler. But the code here only handles the _second_
         * instance of the irq, not the third or fourth. So it is mostly
         * useful for irq hardware that does not mask cleanly in an
         * SMP environment.
         */
        for (;;) {
                spin_unlock(&desc->lock);
                handle_IRQ_event(irq, regs, action);
                spin_lock(&desc->lock);
                
                if (unlikely(!(desc->status & IRQ_PENDING)))
                        break;
                desc->status &= ~IRQ_PENDING;
        }
        desc->status &= ~IRQ_INPROGRESS;
out:
        /*
         * The ->end() handler has to deal with interrupts which got
         * disabled while the handler was running.
         */
        if (irq > 256) BUG();
        desc->handler->end(irq);
        spin_unlock(&desc->lock);

        irq_exit();
        return 1;
}

int can_request_irq(unsigned int irq, unsigned long irqflags)
{
        struct irqaction *action;

        if (irq >= NR_IRQS)
                return 0;
        action = irq_desc[irq].action;
        if (action) {
                if (irqflags & action->flags & SA_SHIRQ)
                        action = NULL;
        }
        return !action;
}

/**
 *      request_irq - allocate an interrupt line
 *      @irq: Interrupt line to allocate
 *      @handler: Function to be called when the IRQ occurs
 *      @irqflags: Interrupt type flags
 *      @devname: An ascii name for the claiming device
 *      @dev_id: A cookie passed back to the handler function
 *
 *      This call allocates interrupt resources and enables the
 *      interrupt line and IRQ handling. From the point this
 *      call is made your handler function may be invoked. Since
 *      your handler function must clear any interrupt the board 
 *      raises, you must take care both to initialise your hardware
 *      and to set up the interrupt handler in the right order.
 *
 *      Dev_id must be globally unique. Normally the address of the
 *      device data structure is used as the cookie. Since the handler
 *      receives this value it makes sense to use it.
 *
 *      If your interrupt is shared you must pass a non NULL dev_id
 *      as this is required when freeing the interrupt.
 *
 *      Flags:
 *
 *      SA_SHIRQ                Interrupt is shared
 *
 *      SA_INTERRUPT            Disable local interrupts while processing
 *
 *      SA_SAMPLE_RANDOM        The interrupt can be used for entropy
 *
 */
 
int request_irq(unsigned int irq, 
                irqreturn_t (*handler)(int, void *, struct pt_regs *),
                unsigned long irqflags, 
                const char * devname,
                void *dev_id)
{
        int retval;
        struct irqaction * action;

#if 1
        /*
         * Sanity-check: shared interrupts should REALLY pass in
         * a real dev-ID, otherwise we'll have trouble later trying
         * to figure out which interrupt is which (messes up the
         * interrupt freeing logic etc).
         */
        if (irqflags & SA_SHIRQ) {
                if (!dev_id)
                        printk("Bad boy: %s (at 0x%x) called us without a dev_id!\n", devname, (&irq)[-1]);
        }
#endif

        if (irq >= NR_IRQS)
                return -EINVAL;
        if (!handler)
                return -EINVAL;

        action = (struct irqaction *)
                        kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
        if (!action)
                return -ENOMEM;

        action->handler = handler;
        action->flags = irqflags;
        cpus_clear(action->mask);
        action->name = devname;
        action->next = NULL;
        action->dev_id = dev_id;

        retval = setup_irq(irq, action);
        if (retval)
                kfree(action);
        return retval;
}

EXPORT_SYMBOL(request_irq);

/**
 *      free_irq - free an interrupt
 *      @irq: Interrupt line to free
 *      @dev_id: Device identity to free
 *
 *      Remove an interrupt handler. The handler is removed and if the
 *      interrupt line is no longer in use by any driver it is disabled.
 *      On a shared IRQ the caller must ensure the interrupt is disabled
 *      on the card it drives before calling this function. The function
 *      does not return until any executing interrupts for this IRQ
 *      have completed.
 *
 *      This function may be called from interrupt context. 
 *
 *      Bugs: Attempting to free an irq in a handler for the same irq hangs
 *            the machine.
 */
 
void free_irq(unsigned int irq, void *dev_id)
{
        irq_desc_t *desc;
        struct irqaction **p;
        unsigned long flags;

        if (irq >= NR_IRQS)
                return;

        desc = irq_desc + irq;
        spin_lock_irqsave(&desc->lock,flags);
        p = &desc->action;
        for (;;) {
                struct irqaction * action = *p;
                if (action) {
                        struct irqaction **pp = p;
                        p = &action->next;
                        if (action->dev_id != dev_id)
                                continue;

                        /* Found it - now remove it from the list of entries */
                        *pp = action->next;
                        if (!desc->action) {
                                desc->status |= IRQ_DISABLED;
                                desc->handler->shutdown(irq);
                        }
                        spin_unlock_irqrestore(&desc->lock,flags);

                        synchronize_irq(irq);
                        kfree(action);
                        return;
                }
                printk("Trying to free free IRQ%d\n",irq);
                spin_unlock_irqrestore(&desc->lock,flags);
                return;
        }
}

EXPORT_SYMBOL(free_irq);

/*
 * IRQ autodetection code..
 *
 * This depends on the fact that any interrupt that
 * comes in on to an unassigned handler will get stuck
 * with "IRQ_WAITING" cleared and the interrupt
 * disabled.
 */

static DECLARE_MUTEX(probe_sem);

/**
 *      probe_irq_on    - begin an interrupt autodetect
 *
 *      Commence probing for an interrupt. The interrupts are scanned
 *      and a mask of potential interrupt lines is returned.
 *
 */
 
unsigned long probe_irq_on(void)
{
        unsigned int i;
        irq_desc_t *desc;
        unsigned long val;
        unsigned long delay;

        down(&probe_sem);
        /* 
         * something may have generated an irq long ago and we want to
         * flush such a longstanding irq before considering it as spurious. 
         */
        for (i = NR_IRQS-1; i > 0; i--)  {
                desc = irq_desc + i;

                spin_lock_irq(&desc->lock);
                if (!irq_desc[i].action) 
                        irq_desc[i].handler->startup(i);
                spin_unlock_irq(&desc->lock);
        }

        /* Wait for longstanding interrupts to trigger. */
        for (delay = jiffies + HZ/50; time_after(delay, jiffies); )
                /* about 20ms delay */ barrier();

        /*
         * enable any unassigned irqs
         * (we must startup again here because if a longstanding irq
         * happened in the previous stage, it may have masked itself)
         */
        for (i = NR_IRQS-1; i > 0; i--) {
                desc = irq_desc + i;

                spin_lock_irq(&desc->lock);
                if (!desc->action) {
                        desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
                        if (desc->handler->startup(i))
                                desc->status |= IRQ_PENDING;
                }
                spin_unlock_irq(&desc->lock);
        }

        /*
         * Wait for spurious interrupts to trigger
         */
        for (delay = jiffies + HZ/10; time_after(delay, jiffies); )
                /* about 100ms delay */ barrier();

        /*
         * Now filter out any obviously spurious interrupts
         */
        val = 0;
        for (i = 0; i < NR_IRQS; i++) {
                irq_desc_t *desc = irq_desc + i;
                unsigned int status;

                spin_lock_irq(&desc->lock);
                status = desc->status;

                if (status & IRQ_AUTODETECT) {
                        /* It triggered already - consider it spurious. */
                        if (!(status & IRQ_WAITING)) {
                                desc->status = status & ~IRQ_AUTODETECT;
                                desc->handler->shutdown(i);
                        } else
                                if (i < 32)
                                        val |= 1 << i;
                }
                spin_unlock_irq(&desc->lock);
        }

        return val;
}

EXPORT_SYMBOL(probe_irq_on);

/*
 * Return a mask of triggered interrupts (this
 * can handle only legacy ISA interrupts).
 */
 
/**
 *      probe_irq_mask - scan a bitmap of interrupt lines
 *      @val:   mask of interrupts to consider
 *
 *      Scan the ISA bus interrupt lines and return a bitmap of
 *      active interrupts. The interrupt probe logic state is then
 *      returned to its previous value.
 *
 *      Note: we need to scan all the irq's even though we will
 *      only return ISA irq numbers - just so that we reset them
 *      all to a known state.
 */
unsigned int probe_irq_mask(unsigned long val)
{
        int i;
        unsigned int mask;

        mask = 0;
        for (i = 0; i < NR_IRQS; i++) {
                irq_desc_t *desc = irq_desc + i;
                unsigned int status;

                spin_lock_irq(&desc->lock);
                status = desc->status;

                if (status & IRQ_AUTODETECT) {
                        if (i < 16 && !(status & IRQ_WAITING))
                                mask |= 1 << i;

                        desc->status = status & ~IRQ_AUTODETECT;
                        desc->handler->shutdown(i);
                }
                spin_unlock_irq(&desc->lock);
        }
        up(&probe_sem);

        return mask & val;
}

/*
 * Return the one interrupt that triggered (this can
 * handle any interrupt source).
 */

/**
 *      probe_irq_off   - end an interrupt autodetect
 *      @val: mask of potential interrupts (unused)
 *
 *      Scans the unused interrupt lines and returns the line which
 *      appears to have triggered the interrupt. If no interrupt was
 *      found then zero is returned. If more than one interrupt is
 *      found then minus the first candidate is returned to indicate
 *      their is doubt.
 *
 *      The interrupt probe logic state is returned to its previous
 *      value.
 *
 *      BUGS: When used in a module (which arguably shouldn't happen)
 *      nothing prevents two IRQ probe callers from overlapping. The
 *      results of this are non-optimal.
 */
 
int probe_irq_off(unsigned long val)
{
        int i, irq_found, nr_irqs;

        nr_irqs = 0;
        irq_found = 0;
        for (i = 0; i < NR_IRQS; i++) {
                irq_desc_t *desc = irq_desc + i;
                unsigned int status;

                spin_lock_irq(&desc->lock);
                status = desc->status;

                if (status & IRQ_AUTODETECT) {
                        if (!(status & IRQ_WAITING)) {
                                if (!nr_irqs)
                                        irq_found = i;
                                nr_irqs++;
                        }
                        desc->status = status & ~IRQ_AUTODETECT;
                        desc->handler->shutdown(i);
                }
                spin_unlock_irq(&desc->lock);
        }
        up(&probe_sem);

        if (nr_irqs > 1)
                irq_found = -irq_found;
        return irq_found;
}

EXPORT_SYMBOL(probe_irq_off);

/* this was setup_x86_irq but it seems pretty generic */
int setup_irq(unsigned int irq, struct irqaction * new)
{
        int shared = 0;
        unsigned long flags;
        struct irqaction *old, **p;
        irq_desc_t *desc = irq_desc + irq;

        if (desc->handler == &no_irq_type)
                return -ENOSYS;

        /*
         * Some drivers like serial.c use request_irq() heavily,
         * so we have to be careful not to interfere with a
         * running system.
         */
        if (new->flags & SA_SAMPLE_RANDOM) {
                /*
                 * This function might sleep, we want to call it first,
                 * outside of the atomic block.
                 * Yes, this might clear the entropy pool if the wrong
                 * driver is attempted to be loaded, without actually
                 * installing a new handler, but is this really a problem,
                 * only the sysadmin is able to do this.
                 */
                rand_initialize_irq(irq);
        }

        /*
         * The following block of code has to be executed atomically
         */
        spin_lock_irqsave(&desc->lock,flags);
        p = &desc->action;
        if ((old = *p) != NULL) {
                /* Can't share interrupts unless both agree to */
                if (!(old->flags & new->flags & SA_SHIRQ)) {
                        spin_unlock_irqrestore(&desc->lock,flags);
                        return -EBUSY;
                }

                /* add new interrupt at end of irq queue */
                do {
                        p = &old->next;
                        old = *p;
                } while (old);
                shared = 1;
        }

        *p = new;

        if (!shared) {
                desc->depth = 0;
                desc->status &= ~(IRQ_DISABLED | IRQ_AUTODETECT | IRQ_WAITING);
                desc->handler->startup(irq);
        }
        spin_unlock_irqrestore(&desc->lock,flags);

        register_irq_proc(irq);
        return 0;
}

static struct proc_dir_entry * root_irq_dir;
static struct proc_dir_entry * irq_dir [NR_IRQS];

#ifdef CONFIG_SMP

static struct proc_dir_entry * smp_affinity_entry [NR_IRQS];

static cpumask_t irq_affinity [NR_IRQS] = { [0 ... NR_IRQS-1] = CPU_MASK_ALL };
static int irq_affinity_read_proc (char *page, char **start, off_t off,
                        int count, int *eof, void *data)
{
        int len = cpumask_scnprintf(page, count, irq_affinity[(long)data]);
        if (count - len < 2)
                return -EINVAL;
        len += sprintf(page + len, "\n");
        return len;
}

static int irq_affinity_write_proc (struct file *file,
                                        const char __user *buffer,
                                        unsigned long count, void *data)
{
        int irq = (long) data, full_count = count, err;
        cpumask_t tmp, new_value;

        if (!irq_desc[irq].handler->set_affinity)
                return -EIO;

        err = cpumask_parse(buffer, count, new_value);

        /*
         * Do not allow disabling IRQs completely - it's a too easy
         * way to make the system unusable accidentally :-) At least
         * one online CPU still has to be targeted.
         */
        cpus_and(tmp, new_value, cpu_online_map);
        if (cpus_empty(tmp))
                return -EINVAL;

        irq_affinity[irq] = new_value;
        irq_desc[irq].handler->set_affinity(irq, new_value);

        return full_count;
}

#endif

#define MAX_NAMELEN 10

static void register_irq_proc (unsigned int irq)
{
        char name [MAX_NAMELEN];

        if (!root_irq_dir || (irq_desc[irq].handler == &no_irq_type) ||
                        irq_dir[irq])
                return;

        memset(name, 0, MAX_NAMELEN);
        sprintf(name, "%d", irq);

        /* create /proc/irq/1234 */
        irq_dir[irq] = proc_mkdir(name, root_irq_dir);

#ifdef CONFIG_SMP
        {
                struct proc_dir_entry *entry;

                /* create /proc/irq/1234/smp_affinity */
                entry = create_proc_entry("smp_affinity", 0600, irq_dir[irq]);

                if (entry) {
                        entry->nlink = 1;
                        entry->data = (void *)(long)irq;
                        entry->read_proc = irq_affinity_read_proc;
                        entry->write_proc = irq_affinity_write_proc;
                }

                smp_affinity_entry[irq] = entry;
        }
#endif
}

void init_irq_proc (void)
{
        int i;

        /* create /proc/irq */
        root_irq_dir = proc_mkdir("irq", NULL);

        /* create /proc/irq/prof_cpu_mask */
        create_prof_cpu_mask(root_irq_dir);

        /*
         * Create entries for all existing IRQs.
         */
        for (i = 0; i < NR_IRQS; i++)
                register_irq_proc(i);
}