[問題] linux中斷旗標-IRQF_TRIGGER_NONE的觸發動作與意義

[hsuya (隱身術??)]

各位先進你好:
小弟剛踏入linux 驅動程式開發

我想請問一下
IRQF_TRIGGER_NONE 的信號觸發方式是怎樣的一個觸發方式？？
在諸多範例中不乏有下面的用法
        if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL))
                {
                printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
                return -EBUSY;
                }

但是在程式上下文中卻沒有用set_irq_type 來宣告該信號是上緣/下緣/level trigger
我很納悶這樣的用法的意義為何?
IRQF_TRIGGER_NONE是哪種觸發方式啊?

#include <linux/input.h>
#include <linux/module.h>
#include <linux/init.h>
#include <asm/irq.h>
include <asm/io.h>
static struct input_dev *button_dev;
static irqreturn_t button_interrupt(int irq, void *dummy)
{
input_report_key(button_dev, BTN_0, inb(BUTTON_PORT) & 1);
input_sync(button_dev);
return IRQ_HANDLED;
}

static int __init button_init(void)
{
 int error;
 if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL))
        {
          printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq);
                return -EBUSY;
           }
button_dev = input_allocate_device();
....



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→ mecs:in interrupt.h :
→ mecs:When requesting an interrupt without specifying a
→ mecs:IRQF_TRIGGER, the setting should be assumed to be
→ mecs:"as already configured", which may be as per machine or
→ mecs:firmware initialisation.
→ hsuya:可以舉例說明嗎 ?此類外部中斷的觸發類型應該決定於哪裡呢?
推 mecs:SOC 裡的裝置