- Andries Brouwer: final isofs pieces.

[davej-history.git] / arch / ia64 / kernel / irq.c

/*
 *      linux/arch/ia64/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/ptrace.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/malloc.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 <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/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 apropriate
 * 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] = { IRQ_DISABLED, &no_irq_type, NULL, 0, SPIN_LOCK_UNLOCKED}};

static void register_irq_proc (unsigned int irq);

/*
 * Special irq handlers.
 */

void no_action(int cpl, void *dev_id, struct pt_regs *regs) { }

/*
 * 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 doesnt deserve
 * a generic callback i think.
 */
#if 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
#if CONFIG_IA64
        printk("Unexpected irq vector 0x%x on CPU %u!\n", irq, smp_processor_id());
#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
};

volatile unsigned long irq_err_count;

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

int get_irq_list(char *buf)
{
        int i, j;
        struct irqaction * action;
        char *p = buf;

        p += sprintf(p, "           ");
        for (j=0; j<smp_num_cpus; j++)
                p += sprintf(p, "CPU%d       ",j);
        *p++ = '\n';

        for (i = 0 ; i < NR_IRQS ; i++) {
                action = irq_desc[i].action;
                if (!action) 
                        continue;
                p += sprintf(p, "%3d: ",i);
#ifndef CONFIG_SMP
                p += sprintf(p, "%10u ", kstat_irqs(i));
#else
                for (j = 0; j < smp_num_cpus; j++)
                        p += sprintf(p, "%10u ",
                                kstat.irqs[cpu_logical_map(j)][i]);
#endif
                p += sprintf(p, " %14s", irq_desc[i].handler->typename);
                p += sprintf(p, "  %s", action->name);

                for (action=action->next; action; action = action->next)
                        p += sprintf(p, ", %s", action->name);
                *p++ = '\n';
        }
        p += sprintf(p, "NMI: ");
        for (j = 0; j < smp_num_cpus; j++)
                p += sprintf(p, "%10u ",
                        nmi_count(cpu_logical_map(j)));
        p += sprintf(p, "\n");
#if defined(CONFIG_SMP) && defined(__i386__)
        p += sprintf(p, "LOC: ");
        for (j = 0; j < smp_num_cpus; j++)
                p += sprintf(p, "%10u ",
                        apic_timer_irqs[cpu_logical_map(j)]);
        p += sprintf(p, "\n");
#endif
        p += sprintf(p, "ERR: %10lu\n", irq_err_count);
        return p - buf;
}


/*
 * Global interrupt locks for SMP. Allow interrupts to come in on any
 * CPU, yet make cli/sti act globally to protect critical regions..
 */

#ifdef CONFIG_SMP
unsigned int global_irq_holder = NO_PROC_ID;
volatile unsigned long global_irq_lock; /* long for set_bit --RR */

extern void show_stack(unsigned long* esp);

static void show(char * str)
{
        int i;
        int cpu = smp_processor_id();

        printk("\n%s, CPU %d:\n", str, cpu);
        printk("irq:  %d [",irqs_running());
        for(i=0;i < smp_num_cpus;i++)
                printk(" %d",local_irq_count(i));
        printk(" ]\nbh:   %d [",spin_is_locked(&global_bh_lock) ? 1 : 0);
        for(i=0;i < smp_num_cpus;i++)
                printk(" %d",local_bh_count(i));

        printk(" ]\nStack dumps:");
#if defined(__ia64__)
        /*
         * We can't unwind the stack of another CPU without access to
         * the registers of that CPU.  And sending an IPI when we're
         * in a potentially wedged state doesn't sound like a smart
         * idea.
         */
#elif defined(__i386__)
        for(i=0;i< smp_num_cpus;i++) {
                unsigned long esp;
                if(i==cpu)
                        continue;
                printk("\nCPU %d:",i);
                esp = init_tss[i].esp0;
                if(esp==NULL) {
                        /* tss->esp0 is set to NULL in cpu_init(),
                         * it's initialized when the cpu returns to user
                         * space. -- manfreds
                         */
                        printk(" <unknown> ");
                        continue;
                }
                esp &= ~(THREAD_SIZE-1);
                esp += sizeof(struct task_struct);
                show_stack((void*)esp);
        }
#else
        You lose...
#endif
        printk("\nCPU %d:",cpu);
        show_stack(NULL);
        printk("\n");
}
        
#define MAXCOUNT 100000000

/*
 * I had a lockup scenario where a tight loop doing
 * spin_unlock()/spin_lock() on CPU#1 was racing with
 * spin_lock() on CPU#0. CPU#0 should have noticed spin_unlock(), but
 * apparently the spin_unlock() information did not make it
 * through to CPU#0 ... nasty, is this by design, do we have to limit
 * 'memory update oscillation frequency' artificially like here?
 *
 * Such 'high frequency update' races can be avoided by careful design, but
 * some of our major constructs like spinlocks use similar techniques,
 * it would be nice to clarify this issue. Set this define to 0 if you
 * want to check whether your system freezes.  I suspect the delay done
 * by SYNC_OTHER_CORES() is in correlation with 'snooping latency', but
 * i thought that such things are guaranteed by design, since we use
 * the 'LOCK' prefix.
 */
#define SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND 0

#if SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND
# define SYNC_OTHER_CORES(x) udelay(x+1)
#else
/*
 * We have to allow irqs to arrive between __sti and __cli
 */
# ifdef __ia64__
#  define SYNC_OTHER_CORES(x) __asm__ __volatile__ ("nop 0")
# else
#  define SYNC_OTHER_CORES(x) __asm__ __volatile__ ("nop")
# endif
#endif

static inline void wait_on_irq(int cpu)
{
        int count = MAXCOUNT;

        for (;;) {

                /*
                 * Wait until all interrupts are gone. Wait
                 * for bottom half handlers unless we're
                 * already executing in one..
                 */
                if (!irqs_running())
                        if (local_bh_count(cpu) || !spin_is_locked(&global_bh_lock))
                                break;

                /* Duh, we have to loop. Release the lock to avoid deadlocks */
                clear_bit(0,&global_irq_lock);

                for (;;) {
                        if (!--count) {
                                show("wait_on_irq");
                                count = ~0;
                        }
                        __sti();
                        SYNC_OTHER_CORES(cpu);
                        __cli();
                        if (irqs_running())
                                continue;
                        if (global_irq_lock)
                                continue;
                        if (!local_bh_count(cpu) && spin_is_locked(&global_bh_lock))
                                continue;
                        if (!test_and_set_bit(0,&global_irq_lock))
                                break;
                }
        }
}

/*
 * This is called when we want to synchronize with
 * interrupts. We may for example tell a device to
 * stop sending interrupts: but to make sure there
 * are no interrupts that are executing on another
 * CPU we need to call this function.
 */
void synchronize_irq(void)
{
        if (irqs_running()) {
                /* Stupid approach */
                cli();
                sti();
        }
}

static inline void get_irqlock(int cpu)
{
        if (test_and_set_bit(0,&global_irq_lock)) {
                /* do we already hold the lock? */
                if (cpu == global_irq_holder)
                        return;
                /* Uhhuh.. Somebody else got it. Wait.. */
                do {
                        do {
                        } while (test_bit(0,&global_irq_lock));
                } while (test_and_set_bit(0,&global_irq_lock));         
        }
        /* 
         * We also to make sure that nobody else is running
         * in an interrupt context. 
         */
        wait_on_irq(cpu);

        /*
         * Ok, finally..
         */
        global_irq_holder = cpu;
}

#define EFLAGS_IF_SHIFT 9

/*
 * A global "cli()" while in an interrupt context
 * turns into just a local cli(). Interrupts
 * should use spinlocks for the (very unlikely)
 * case that they ever want to protect against
 * each other.
 *
 * If we already have local interrupts disabled,
 * this will not turn a local disable into a
 * global one (problems with spinlocks: this makes
 * save_flags+cli+sti usable inside a spinlock).
 */
void __global_cli(void)
{
        unsigned int flags;

#ifdef __ia64__
        __save_flags(flags);
        if (flags & IA64_PSR_I) {
                int cpu = smp_processor_id();
                __cli();
                if (!local_irq_count(cpu))
                        get_irqlock(cpu);
        }
#else
        __save_flags(flags);
        if (flags & (1 << EFLAGS_IF_SHIFT)) {
                int cpu = smp_processor_id();
                __cli();
                if (!local_irq_count(cpu))
                        get_irqlock(cpu);
        }
#endif
}

void __global_sti(void)
{
        int cpu = smp_processor_id();

        if (!local_irq_count(cpu))
                release_irqlock(cpu);
        __sti();
}

/*
 * SMP flags value to restore to:
 * 0 - global cli
 * 1 - global sti
 * 2 - local cli
 * 3 - local sti
 */
unsigned long __global_save_flags(void)
{
        int retval;
        int local_enabled;
        unsigned long flags;
        int cpu = smp_processor_id();

        __save_flags(flags);
#ifdef __ia64__
        local_enabled = (flags & IA64_PSR_I) != 0;
#else
        local_enabled = (flags >> EFLAGS_IF_SHIFT) & 1;
#endif
        /* default to local */
        retval = 2 + local_enabled;

        /* check for global flags if we're not in an interrupt */
        if (!local_irq_count(cpu)) {
                if (local_enabled)
                        retval = 1;
                if (global_irq_holder == cpu)
                        retval = 0;
        }
        return retval;
}

void __global_restore_flags(unsigned long flags)
{
        switch (flags) {
        case 0:
                __global_cli();
                break;
        case 1:
                __global_sti();
                break;
        case 2:
                __cli();
                break;
        case 3:
                __sti();
                break;
        default:
                printk("global_restore_flags: %08lx (%08lx)\n",
                        flags, (&flags)[-1]);
        }
}

#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;
        int cpu = smp_processor_id();

        irq_enter(cpu, irq);

        status = 1;     /* Force the "do bottom halves" bit */

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

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

        irq_exit(cpu, irq);

        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. 
 */
void inline 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);
}

/*
 * Synchronous version of the above, making sure the IRQ is
 * no longer running on any other IRQ..
 */
void disable_irq(unsigned int irq)
{
        disable_irq_nosync(irq);

#ifdef CONFIG_SMP
        if (!local_irq_count(smp_processor_id())) {
                do {
                        barrier();
                } while (irq_desc[irq].status & IRQ_INPROGRESS);
        }
#endif
}

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() unbalanced from %p\n", (void *) __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).
 */
unsigned int do_IRQ(unsigned long 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)
         */
        int cpu = smp_processor_id();
        irq_desc_t *desc = irq_desc + irq;
        struct irqaction * action;
        unsigned int status;

        kstat.irqs[cpu][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 (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
                action = desc->action;
                status &= ~IRQ_PENDING; /* we commit to handling */
                if (!(status & IRQ_PER_CPU))
                        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 (!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 (!(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.
         */
        desc->handler->end(irq);
        spin_unlock(&desc->lock);

        return 1;
}

int request_irq(unsigned int irq, 
                void (*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_KERNEL);
        if (!action)
                return -ENOMEM;

        action->handler = handler;
        action->flags = irqflags;
        action->mask = 0;
        action->name = devname;
        action->next = NULL;
        action->dev_id = dev_id;

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

#ifdef CONFIG_SMP
                        /* Wait to make sure it's not being used on another CPU */
                        while (desc->status & IRQ_INPROGRESS)
                                barrier();
#endif
                        kfree(action);
                        return;
                }
                printk("Trying to free free IRQ%d\n",irq);
                spin_unlock_irqrestore(&desc->lock,flags);
                return;
        }
}

/*
 * 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.
 */
unsigned long probe_irq_on(void)
{
        unsigned int i;
        irq_desc_t *desc;
        unsigned long val;
        unsigned long delay;

        /* 
         * 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 */ synchronize_irq();

        /*
         * 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 */ synchronize_irq();

        /*
         * 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;
}

/*
 * Return a mask of triggered interrupts (this
 * can handle only legacy ISA interrupts).
 */
unsigned int probe_irq_mask(unsigned long val)
{
        int i;
        unsigned int mask;

        mask = 0;
        for (i = 0; i < 16; 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))
                                mask |= 1 << i;

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

        return mask & val;
}

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

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

/* 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;

        /*
         * 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;
                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];
static struct proc_dir_entry * smp_affinity_entry [NR_IRQS];

static unsigned long irq_affinity [NR_IRQS] = { [0 ... NR_IRQS-1] = ~0UL };

#define HEX_DIGITS 8

static int irq_affinity_read_proc (char *page, char **start, off_t off,
                        int count, int *eof, void *data)
{
        if (count < HEX_DIGITS+1)
                return -EINVAL;
        return sprintf (page, "%08lx\n", irq_affinity[(long)data]);
}

static unsigned int parse_hex_value (const char *buffer,
                unsigned long count, unsigned long *ret)
{
        unsigned char hexnum [HEX_DIGITS];
        unsigned long value;
        int i;

        if (!count)
                return -EINVAL;
        if (count > HEX_DIGITS)
                count = HEX_DIGITS;
        if (copy_from_user(hexnum, buffer, count))
                return -EFAULT;

        /*
         * Parse the first 8 characters as a hex string, any non-hex char
         * is end-of-string. '00e1', 'e1', '00E1', 'E1' are all the same.
         */
        value = 0;

        for (i = 0; i < count; i++) {
                unsigned int c = hexnum[i];

                switch (c) {
                        case '0' ... '9': c -= '0'; break;
                        case 'a' ... 'f': c -= 'a'-10; break;
                        case 'A' ... 'F': c -= 'A'-10; break;
                default:
                        goto out;
                }
                value = (value << 4) | c;
        }
out:
        *ret = value;
        return 0;
}

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

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

        err = parse_hex_value(buffer, count, &new_value);

#if CONFIG_SMP
        /*
         * 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.
         */
        if (!(new_value & cpu_online_map))
                return -EINVAL;
#endif

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

        return full_count;
}

static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
                        int count, int *eof, void *data)
{
        unsigned long *mask = (unsigned long *) data;
        if (count < HEX_DIGITS+1)
                return -EINVAL;
        return sprintf (page, "%08lx\n", *mask);
}

static int prof_cpu_mask_write_proc (struct file *file, const char *buffer,
                                        unsigned long count, void *data)
{
        unsigned long *mask = (unsigned long *) data, full_count = count, err;
        unsigned long new_value;

        err = parse_hex_value(buffer, count, &new_value);
        if (err)
                return err;

        *mask = new_value;
        return full_count;
}

#define MAX_NAMELEN 10

static void register_irq_proc (unsigned int irq)
{
        struct proc_dir_entry *entry;
        char name [MAX_NAMELEN];

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

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

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

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

        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;
}

unsigned long prof_cpu_mask = -1;

void init_irq_proc (void)
{
        struct proc_dir_entry *entry;
        int i;

        /* create /proc/irq */
        root_irq_dir = proc_mkdir("irq", 0);

        /* create /proc/irq/prof_cpu_mask */
        entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);

        entry->nlink = 1;
        entry->data = (void *)&prof_cpu_mask;
        entry->read_proc = prof_cpu_mask_read_proc;
        entry->write_proc = prof_cpu_mask_write_proc;

        /*
         * Create entries for all existing IRQs.
         */
        for (i = 0; i < NR_IRQS; i++) {
                if (irq_desc[i].handler == &no_irq_type)
                        continue;
                register_irq_proc(i);
        }
}