Linux-2.6.12-rc2

[mirror_ubuntu-artful-kernel.git] / kernel / irq / manage.c

/*
 * linux/kernel/irq/manage.c
 *
 * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
 *
 * This file contains driver APIs to the irq subsystem.
 */

#include <linux/irq.h>
#include <linux/module.h>
#include <linux/random.h>
#include <linux/interrupt.h>

#include "internals.h"

#ifdef CONFIG_SMP

cpumask_t irq_affinity[NR_IRQS] = { [0 ... NR_IRQS-1] = CPU_MASK_ALL };

/**
 *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
 *
 *      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 synchronize_irq(unsigned int irq)
{
        struct irq_desc *desc = irq_desc + irq;

        while (desc->status & IRQ_INPROGRESS)
                cpu_relax();
}

EXPORT_SYMBOL(synchronize_irq);

#endif

/**
 *      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 may be called from IRQ context.
 */
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);
}

EXPORT_SYMBOL(disable_irq_nosync);

/**
 *      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)
{
        irq_desc_t *desc = irq_desc + irq;

        disable_irq_nosync(irq);
        if (desc->action)
                synchronize_irq(irq);
}

EXPORT_SYMBOL(disable_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 0:
                WARN_ON(1);
                break;
        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--;
        }
        spin_unlock_irqrestore(&desc->lock, flags);
}

EXPORT_SYMBOL(enable_irq);

/*
 * Internal function that tells the architecture code whether a
 * particular irq has been exclusively allocated or is available
 * for driver use.
 */
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;
}

/*
 * Internal function to register an irqaction - typically used to
 * allocate special interrupts that are part of the architecture.
 */
int setup_irq(unsigned int irq, struct irqaction * new)
{
        struct irq_desc *desc = irq_desc + irq;
        struct irqaction *old, **p;
        unsigned long flags;
        int shared = 0;

        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 | IRQ_INPROGRESS);
                if (desc->handler->startup)
                        desc->handler->startup(irq);
                else
                        desc->handler->enable(irq);
        }
        spin_unlock_irqrestore(&desc->lock,flags);

        new->irq = irq;
        register_irq_proc(irq);
        new->dir = NULL;
        register_handler_proc(irq, new);

        return 0;
}

/**
 *      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 must not be called from interrupt context.
 */
void free_irq(unsigned int irq, void *dev_id)
{
        struct irq_desc *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;
                                if (desc->handler->shutdown)
                                        desc->handler->shutdown(irq);
                                else
                                        desc->handler->disable(irq);
                        }
                        spin_unlock_irqrestore(&desc->lock,flags);
                        unregister_handler_proc(irq, action);

                        /* Make sure it's not being used on another CPU */
                        synchronize_irq(irq);
                        kfree(action);
                        return;
                }
                printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
                spin_unlock_irqrestore(&desc->lock,flags);
                return;
        }
}

EXPORT_SYMBOL(free_irq);

/**
 *      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)
{
        struct irqaction * action;
        int retval;

        /*
         * Sanity-check: shared interrupts must 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) && !dev_id)
                return -EINVAL;
        if (irq >= NR_IRQS)
                return -EINVAL;
        if (!handler)
                return -EINVAL;

        action = 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);