二 注册中止
这部分咱们以3sc2410下的watchdog的中止为例来解说中止的注册及调用进程。
drivers/char/watchdog/s3c2410_wdt.c:
static int s3c2410wdt_probe(struct platform_device *pdev)
{
……
/*注册中止*/
ret = request_irq(res->start, s3c2410wdt_irq, 0, pdev->name, pdev);
……
}
在s3c2410wdt_probe函数中为watchdog注册了一个中止，中止号为IRQ_WDT，
#define IRQ_WDTS3C2410_IRQ(9)
中止处理函数是s3c2410wdt_irq。
咱们来看request_irq是怎么完结的：
kernel/irq/Manage.c:
/
*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:
*
*IRQF_SHAREDInterrupt is shared
*IRQF_DISABLEDDisable local interrupts while processing
*IRQF_SAMPLE_RANDOMThe 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;
#ifdef CONFIG_LOCKDEP
/*
* Lockdep wants atomic interrupt handlers:
*/
irqflags |= SA_INTERRUPT;
#endif
/*
* Sanity-check: shared interrupts must pass in a real dev-ID,
* otherwise well have trouble later trying to figure out
* which interrupt is which (messes up the interrupt freeing
* logic etc).
*/
/*答应同享的中止有必要要有一个绝无仅有的dev_id,看上面函数的解说
if ((irqflags & IRQF_SHARED) && !dev_id)
return -EINVAL;
if (irq >= NR_IRQS) /*中止号是否合法*/
return -EINVAL;
/*这个符号对s3c2410来说在s3c24xx_init_irq里经过调用set_irq_flags()被去掉了*/
if (irq_desc[irq].status & IRQ_NOREQUEST)
return -EINVAL;
if (!handler)/*中止例程*/
return -EINVAL;
/*分配一个irqaction目标，来保存这个中止信息*/
action = kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
if (!action)
return -ENOMEM;
/*保存中止例程等信息*/
action->handler = handler;
action->flags = irqflags;
cpus_clear(action->mask);/*铲除相应位*/
action->name = devname;
action->next = NULL;
action->dev_id = dev_id;
select_smp_affinity(irq);
retval = setup_irq(irq, action);/*请求中止*/
if (retval)
kfree(action);
return retval;
}
该函数的功用及参数意义在函数头有详细的阐明，这儿就不多介绍了，值得注意的是咱们在请求中止之前，有必要要去掉该中止的IRQ_NOREQUEST符号(体系初始化的时分赋了这个符号)， 详细方法是调用set_irq_flags()函数。
接着看setup_irq
kernel/irq/Manage.c:
/*
* 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; /*获取保存该中止的中止描述符地址*/
struct irqaction *old, p;
unsigned long flags;
int shared = 0;
if (irq >= NR_IRQS)
return -EINVAL;
/*关于s3c2410的中止在s3c24xx_init_irq里现已初始化过了*/
if (desc->chip == &no_irq_chip)
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 & IRQF_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
*/
/*
*下面if代码段主要是检查该中止是否能够同享，如能够，则把中止例程链入中止例程
* list中,至于中止同享的条件有：1触发方法相同，2都答应中止同享*/
spin_lock_irqsave(&desc->lock, flags);
p = &desc->action;
old = *p;
if (old) { /*关于IRQ_WDT，这个if不成立，但它现已设置了handle_irq喔*/
/*
* Cant share interrupts unless both agree to and are
* the same type (level, edge, polarity). So both flag
* fields must have IRQF_SHARED set and the bits which
* set the trigger type must match.
*/
/*判别能否同享中止*/
if (!((old->flags & new->flags) & IRQF_SHARED) ||
((old->flags ^ new->flags) & IRQF_TRIGGER_MASK))
goto mismatch;
#if defined(CONFIG_IRQ_PER_CPU)
/* All handlers must agree on per-cpuness */
if ((old->flags & IRQF_PERCPU) !=
(new->flags & IRQF_PERCPU))
goto mismatch;
#endif
/* add new interrupt at end of irq queue */
/*把中止例程参加list中*/
do {
p = &old->next;
old = *p;
} while (old);
shared = 1;
}
*p = new;/*该行很要害， 它把中止的处理函数增加到该中止描述符的中止例程list里*/
#if defined(CONFIG_IRQ_PER_CPU)
if (new->flags & IRQF_PERCPU)
desc->status |= IRQ_PER_CPU;
#endif
if (!shared) {
/*关于IRQ_WDT来说这步是剩余的，初始化的时分已做过*/
irq_chip_set_defaults(desc->chip);
/* Setup the type (level, edge polarity) if configured: */
/*关于IRQ_WDT来说，没有界说触发方法， 即默许触发方法*/
if (new->flags & IRQF_TRIGGER_MASK) {
/*假如要设触发方法，则调用渠道特定的函数，因而假如咱们的渠道要完结该功用则必*须要在irq_chip目标里参加对set_type函数的支撑*/
if (desc->chip && desc->chip->set_type)
desc->chip->set_type(irq,
new->flags & IRQF_TRIGGER_MASK);
else
/*
* IRQF_TRIGGER_* but the PIC does not support
* multiple flow-types?
*/
printk(KERN_WARNING “No IRQF_TRIGGER set_type “
“function for IRQ %d (%s)/n”, irq,
desc->chip ? desc->chip->name :
“unknown”);
} else
/*这函数仅仅简略的检查是否有handle_irq*/
compat_irq_chip_set_default_handler(desc);
/*去掉中止的相关状况，让它安排妥当*/
desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
IRQ_INPROGRESS);
if (!(desc->status & IRQ_NOAUTOEN)) {
/*使能该中止*/
desc->depth = 0;
desc->status &= ~IRQ_DISABLED;
if (desc->chip->startup)
desc->chip->startup(irq); /*渠道相关函数*/
else
desc->chip->enable(irq);/*渠道相关函数*/
} else
/* Undo nested disables: */
desc->depth = 1;
}
spin_unlock_irqrestore(&desc->lock, flags);
new->irq = irq;
register_irq_proc(irq);/*在/proc/irq/下创立该中止的一个文件*/
new->dir = NULL;
register_handler_proc(irq, new); /*为/proc/irq/下创立的文件设置处理函数*/
return 0;
mismatch:
spin_unlock_irqrestore(&desc->lock, flags);
if (!(new->flags & IRQF_PROBE_SHARED)) {
printk(KERN_ERR “IRQ handler type mismatch for IRQ %d/n”, irq);
dump_stack();
}
return -EBUSY;
}
该函数主要是装置了一个中止，并使能它。 咱们先看使能函数，它是渠道相关的，关于s3c2410的IRQ_WDT来说运用的是默许的使能函数(default_startup(),初始化赋值)，假如咱们要运用自己的使能函数，只要在chip目标里增加就行了。
kernel/irq/Chip.c:
static unsigned int default_startup(unsigned int irq)
{
irq_desc[irq].chip->enable(irq);
return 0;
}
关于IRQ_WDT来说调用的irq_desc[irq].chip->enable(irq)仍是默许函数：default_enable（）
kernel/irq/Chip.c:
static void default_enable(unsigned int irq)
{
struct irq_desc *desc = irq_desc + irq;
desc->chip->unmask(irq);/*unmask该中止*/
desc->status &= ~IRQ_MASKED;
}
，关于IRQ_WDT来说这次的调用desc->chip->unmask(irq)，实际上是s3c_irq_unmask,详细可检查前面剖析的chip目标。
arch/arm/mach-s3c2410/Irq.c:
static void
s3c_irq_unmask(unsigned int irqno)
{
unsigned long mask;
if (irqno != IRQ_TIMER4 && irqno != IRQ_EINT8t23)
irqdbf2(“s3c_irq_unmask %d/n”, irqno);
irqno -= IRQ_EINT0;
mask = __raw_readl(S3C2410_INTMSK);
mask &= ~(1UL << irqno);
__raw_writel(mask, S3C2410_INTMSK);
}
对着s3c2410的data sheet一看就知道了， 便是翻开相应中止。
至此中止处理函数装置好了，中止也翻开了，体系就能够正确的呼应中止了。
Ok，到此为止IRQ_WDT的中止注册进程已完结，此刻的中止描述符如下所示：
