irq.c

底层驱动开发

/*
 *	linux/arch/alpha/kernel/irq.c
 *
 *	Copyright (C) 1995 Linus Torvalds
 *
 * 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.
 */

#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/init.h>
#include <linux/irq.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/profile.h>
#include <linux/bitops.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/uaccess.h>

/*
 * 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);

volatile unsigned long irq_err_count;

/*
 * 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 no_irq_enable_disable(unsigned int irq) { }
static unsigned int no_irq_startup(unsigned int irq) { return 0; }

static void
no_irq_ack(unsigned int irq)
{
	irq_err_count++;
	printk(KERN_CRIT "Unexpected IRQ trap at vector %u\n", irq);
}

struct hw_interrupt_type no_irq_type = {
	.typename	= "none",
	.startup	= no_irq_startup,
	.shutdown	= no_irq_enable_disable,
	.enable		= no_irq_enable_disable,
	.disable	= no_irq_enable_disable,
	.ack		= no_irq_ack,
	.end		= no_irq_enable_disable,
};

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;

	do {
		if (!(action->flags & SA_INTERRUPT))
			local_irq_enable();
		else
			local_irq_disable();

		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. 
 */
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);
	synchronize_irq(irq);
}

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(KERN_ERR "enable_irq() unbalanced from %p\n",
		       __builtin_return_address(0));
	}
	spin_unlock_irqrestore(&desc->lock, flags);
}

int
setup_irq(unsigned int irq, struct irqaction * new)
{
	int shared = 0;
	struct irqaction *old, **p;
	unsigned long flags;
	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|IRQ_INPROGRESS);
		desc->handler->startup(irq);
	}
	spin_unlock_irqrestore(&desc->lock,flags);

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

static void
select_smp_affinity(int irq)
{
	static int last_cpu;
	int cpu = last_cpu + 1;

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

	while (!cpu_possible(cpu))
		cpu = (cpu < (NR_CPUS-1) ? cpu + 1 : 0);
	last_cpu = cpu;

	irq_affinity[irq] = cpumask_of_cpu(cpu);
	irq_desc[irq].handler->set_affinity(irq, cpumask_of_cpu(cpu));
}

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 new_value;

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

	err = cpumask_parse(buffer, count, new_value);

	/* The special value 0 means release control of the
	   affinity to kernel.  */
	cpus_and(new_value, new_value, cpu_online_map);
	if (cpus_empty(new_value)) {
		irq_user_affinity[irq] = 0;
		select_smp_affinity(irq);
	}
	/* 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.  */
	else {
		irq_affinity[irq] = new_value;
		irq_user_affinity[irq] = 1;
		irq_desc[irq].handler->set_affinity(irq, new_value);
	}

	return full_count;
}

#endif /* CONFIG_SMP */

#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 
	if (irq_desc[irq].handler->set_affinity) {
		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);

#ifdef CONFIG_SMP 
	/* create /proc/irq/prof_cpu_mask */
	create_prof_cpu_mask(root_irq_dir);
#endif

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

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

#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) && !dev_id) {
		printk(KERN_ERR
		       "Bad boy: %s (at %p) called us without a dev_id!\n",
		       devname, __builtin_return_address(0));
	}
#endif

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

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