request_threaded_irq()解读
来源:互联网 发布:ios数据持久化方式 编辑:程序博客网 时间:2024/05/22 19:27
http://blog.csdn.net/lamdoc/article/details/7663049
1. 这个中断函数比较有意思,不仅定义了中断处理函数ads7846_hard_irq(),还会创建一个新线程,用来运行指定函数函数ads7846_irq()。具体应用:
- err = request_threaded_irq(spi->irq, ads7846_hard_irq, ads7846_irq,
- irq_flags, spi->dev.driver->name, ts);
- /**
- * request_threaded_irq - allocate an interrupt line
- * @irq: Interrupt line to allocate
- * @handler: Function to be called when the IRQ occurs.
- * Primary handler for threaded interrupts
- * If NULL and thread_fn != NULL the default
- * primary handler is installed
- * @thread_fn: Function called from the irq handler thread
- * If NULL, no irq thread is created
- * @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.
- *
- * If you want to set up a threaded irq handler for your device
- * then you need to supply @handler and @thread_fn. @handler ist
- * still called in hard interrupt context and has to check
- * whether the interrupt originates from the device. If yes it
- * needs to disable the interrupt on the device and return
- * IRQ_WAKE_THREAD which will wake up the handler thread and run
- * @thread_fn. This split handler design is necessary to support
- * shared interrupts.
- *
- * 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_SHARED Interrupt is shared
- * IRQF_SAMPLE_RANDOM The interrupt can be used for entropy
- * IRQF_TRIGGER_* Specify active edge(s) or level
- *
- */
- int request_threaded_irq(unsigned int irq, irq_handler_t handler,
- irq_handler_t thread_fn, unsigned long irqflags,
- const char *devname, void *dev_id)
- {
- struct irqaction *action;
- struct irq_desc *desc;
- 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 & IRQF_SHARED) && !dev_id)
- return -EINVAL;
- desc = irq_to_desc(irq);
- if (!desc)
- return -EINVAL;
- if (desc->status & IRQ_NOREQUEST)
- return -EINVAL;
- if (!handler) {
- if (!thread_fn)
- return -EINVAL;
- handler = irq_default_primary_handler;
- }
- action = kzalloc(sizeof(struct irqaction), GFP_KERNEL); //分配irqaction内存
- if (!action)
- return -ENOMEM;
- action->handler = handler;
- action->thread_fn = thread_fn;
- action->flags = irqflags;
- action->name = devname;
- action->dev_id = dev_id;
- chip_bus_lock(desc);
- retval = __setup_irq(irq, desc, action); //锁上后,这句才是动作
- chip_bus_sync_unlock(desc);
- if (retval)
- kfree(action);
- #ifdef CONFIG_DEBUG_SHIRQ
- if (!retval && (irqflags & IRQF_SHARED)) {
- /*
- * It's a shared IRQ -- the driver ought to be prepared for it
- * to happen immediately, so let's make sure....
- * We disable the irq to make sure that a 'real' IRQ doesn't
- * run in parallel with our fake.
- */
- unsigned long flags;
- disable_irq(irq);
- local_irq_save(flags);
- handler(irq, dev_id);
- local_irq_restore(flags);
- enable_irq(irq);
- }
- #endif
- return retval;
- }
- EXPORT_SYMBOL(request_threaded_irq);
3. __setup_irq()定义如下:
- /*
- * Internal function to register an irqaction - typically used to
- * allocate special interrupts that are part of the architecture.
- */
- static int
- __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
- {
- struct irqaction *old, **old_ptr;
- const char *old_name = NULL;
- unsigned long flags;
- int nested, shared = 0;
- int ret;
- if (!desc)
- return -EINVAL;
- if (desc->irq_data.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);
- }
- /* Oneshot interrupts are not allowed with shared */
- if ((new->flags & IRQF_ONESHOT) && (new->flags & IRQF_SHARED))
- return -EINVAL;
- /*
- * Check whether the interrupt nests into another interrupt
- * thread.
- */
- nested = desc->status & IRQ_NESTED_THREAD;
- if (nested) {
- if (!new->thread_fn)
- return -EINVAL;
- /*
- * Replace the primary handler which was provided from
- * the driver for non nested interrupt handling by the
- * dummy function which warns when called.
- */
- new->handler = irq_nested_primary_handler;
- }
- /*
- * Create a handler thread when a thread function is supplied
- * and the interrupt does not nest into another interrupt
- * thread.
- */
- if (new->thread_fn && !nested) {
- struct task_struct *t;
- t = kthread_create(irq_thread, new, "irq/%d-%s", irq, //kthread_create()就是创建新内核线程的动作了
- new->name);
- if (IS_ERR(t))
- return PTR_ERR(t);
- /*
- * We keep the reference to the task struct even if
- * the thread dies to avoid that the interrupt code
- * references an already freed task_struct.
- */
- get_task_struct(t);
- new->thread = t;
- }
- /*
- * The following block of code has to be executed atomically
- */
- raw_spin_lock_irqsave(&desc->lock, flags);
- old_ptr = &desc->action;
- old = *old_ptr;
- if (old) {
- /*
- * Can't 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.
- */
- if (!((old->flags & new->flags) & IRQF_SHARED) ||
- ((old->flags ^ new->flags) & IRQF_TRIGGER_MASK)) {
- old_name = old->name;
- 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 */
- do {
- old_ptr = &old->next;
- old = *old_ptr;
- } while (old);
- shared = 1;
- }
- if (!shared) {
- irq_chip_set_defaults(desc->irq_data.chip);
- init_waitqueue_head(&desc->wait_for_threads);
- /* Setup the type (level, edge polarity) if configured: */
- if (new->flags & IRQF_TRIGGER_MASK) {
- ret = __irq_set_trigger(desc, irq,
- new->flags & IRQF_TRIGGER_MASK);
- if (ret)
- goto out_thread;
- } else
- compat_irq_chip_set_default_handler(desc);
- #if defined(CONFIG_IRQ_PER_CPU)
- if (new->flags & IRQF_PERCPU)
- desc->status |= IRQ_PER_CPU;
- #endif
- desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
- IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
- if (new->flags & IRQF_ONESHOT)
- desc->status |= IRQ_ONESHOT;
- if (!(desc->status & IRQ_NOAUTOEN)) {
- desc->depth = 0;
- desc->status &= ~IRQ_DISABLED;
- desc->irq_data.chip->irq_startup(&desc->irq_data);
- } else
- /* Undo nested disables: */
- desc->depth = 1;
- /* Exclude IRQ from balancing if requested */
- if (new->flags & IRQF_NOBALANCING)
- desc->status |= IRQ_NO_BALANCING;
- /* Set default affinity mask once everything is setup */
- setup_affinity(irq, desc);
- } else if ((new->flags & IRQF_TRIGGER_MASK)
- && (new->flags & IRQF_TRIGGER_MASK)
- != (desc->status & IRQ_TYPE_SENSE_MASK)) {
- /* hope the handler works with the actual trigger mode... */
- pr_warning("IRQ %d uses trigger mode %d; requested %d\n",
- irq, (int)(desc->status & IRQ_TYPE_SENSE_MASK),
- (int)(new->flags & IRQF_TRIGGER_MASK));
- }
- new->irq = irq;
- *old_ptr = new;
- /* Reset broken irq detection when installing new handler */
- desc->irq_count = 0;
- desc->irqs_unhandled = 0;
- /*
- * Check whether we disabled the irq via the spurious handler
- * before. Reenable it and give it another chance.
- */
- if (shared && (desc->status & IRQ_SPURIOUS_DISABLED)) {
- desc->status &= ~IRQ_SPURIOUS_DISABLED;
- __enable_irq(desc, irq, false);
- }
- raw_spin_unlock_irqrestore(&desc->lock, flags);
- /*
- * Strictly no need to wake it up, but hung_task complains
- * when no hard interrupt wakes the thread up.
- */
- if (new->thread)
- wake_up_process(new->thread);
- register_irq_proc(irq, desc);
- new->dir = NULL;
- register_handler_proc(irq, new);
- return 0;
- mismatch:
- #ifdef CONFIG_DEBUG_SHIRQ
- if (!(new->flags & IRQF_PROBE_SHARED)) {
- printk(KERN_ERR "IRQ handler type mismatch for IRQ %d\n", irq);
- if (old_name)
- printk(KERN_ERR "current handler: %s\n", old_name);
- dump_stack();
- }
- #endif
- ret = -EBUSY;
- out_thread:
- raw_spin_unlock_irqrestore(&desc->lock, flags);
- if (new->thread) {
- struct task_struct *t = new->thread;
- new->thread = NULL;
- if (likely(!test_bit(IRQTF_DIED, &new->thread_flags)))
- kthread_stop(t);
- put_task_struct(t);
- }
- return ret;
- }
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