#define gpiochip_add_data(chip, data) gpiochip_add_data_with_key(chip, data, NULL, NULL)
int gpiochip_add_data_with_key(struct gpio_chip *chip, void *data,
			       struct lock_class_key *lock_key,
			       struct lock_class_key *request_key)
{
	unsigned long	flags;
	int		status = 0;
	unsigned	i;
	int		base = chip->base;
	struct gpio_device *gdev;

	 // 每一个bank都都应一个唯一的gpio_device和gpio_chip
	gdev = kzalloc(sizeof(*gdev), GFP_KERNEL);

	gdev->dev.bus = &gpio_bus_type;
	gdev->chip = chip;
	chip->gpiodev = gdev;
	if (chip->parent) {
		gdev->dev.parent = chip->parent;
		gdev->dev.of_node = chip->parent->of_node;
	}

#ifdef CONFIG_OF_GPIO
	/* If the gpiochip has an assigned OF node this takes precedence */
	if (chip->of_node)
		gdev->dev.of_node = chip->of_node;
	else
		chip->of_node = gdev->dev.of_node;
#endif
	// 分配一个唯一的id
	gdev->id = ida_simple_get(&gpio_ida, 0, 0, GFP_KERNEL);

	dev_set_name(&gdev->dev, "gpiochip%d", gdev->id);
	device_initialize(&gdev->dev);
	dev_set_drvdata(&gdev->dev, gdev);
	if (chip->parent && chip->parent->driver)
		gdev->owner = chip->parent->driver->owner;
	else if (chip->owner)
		/* TODO: remove chip->owner */
		gdev->owner = chip->owner;
	else
		gdev->owner = THIS_MODULE;
	
	// 为这个chip下的每一个gpio都要分配一个gpio_desc结构体
	gdev->descs = kcalloc(chip->ngpio, sizeof(gdev->descs[0]), GFP_KERNEL);

	gdev->label = kstrdup_const(chip->label ?: "unknown", GFP_KERNEL);
	
	// 这个chip中含有的gpio的个数
	gdev->ngpio = chip->ngpio;
	//gdev->data代表这个bank
	gdev->data = data;

	spin_lock_irqsave(&gpio_lock, flags);

	// base表示的是这个bank在系统中的逻辑gpio号
	gdev->base = base;
	
	// 将这个bank对应的gpio_device添加到全局链表gpio_devices中
	// 在添加的时候会根据gdev->base和ngpio在gpio_devices链表中找到合适的位置
	status = gpiodev_add_to_list(gdev);

	spin_unlock_irqrestore(&gpio_lock, flags);

   	/*为每个GPIO分配gpio_desc，建立与gdev的联系*/
	for (i = 0; i < chip->ngpio; i++) {
		struct gpio_desc *desc = &gdev->descs[i];

		desc->gdev = gdev;

		desc->flags = !chip->direction_input ? (1 << FLAG_IS_OUT) : 0;
	}

	// 默认这个chip下的所有gpio都是可以产生中断
	status = gpiochip_irqchip_init_valid_mask(chip);

	status = gpiochip_init_valid_mask(chip);
	/*为该bank添加irq_chip,并创建一个irq_domain
	只是创建了irq domain，还没有存放任何中断映射关系，在需要的时候才会映射。*/
	status = gpiochip_add_irqchip(chip, lock_key, request_key);

	status = of_gpiochip_add(chip);

	acpi_gpiochip_add(chip);

	machine_gpiochip_add(chip);

	if (gpiolib_initialized) {
		status = gpiochip_setup_dev(gdev);
	}
	return 0;
}

---> of_gpiochip_add(struct gpio_chip *chip)

int of_gpiochip_add(struct gpio_chip *chip)
{
	int status;
......
	if (!chip->of_xlate) {
		/*pio_chip的of_gpio_n_cells被赋值为2，表示引用一个gpio资源需要两个参数，
		负责解析这两个参数函数以的of_xlate函数为of_gpio_simple_xlate，
		其中第一个参数表示gpio号(在对应的bank中)，第二个表示flag*/
		chip->of_gpio_n_cells = 2;
		chip->of_xlate = of_gpio_simple_xlate;
	}

int of_gpio_simple_xlate(struct gpio_chip *gc,
			 const struct of_phandle_args *gpiospec, u32 *flags)
{
	......
	if (flags)		// 第二个参数表示的是flag
		*flags = gpiospec->args[1];
 	// 第一个参数表示的是gpio号
	return gpiospec->args[0];
}

static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,
				struct lock_class_key *lock_key,
				struct lock_class_key *request_key)
{
	struct irq_chip *irqchip = gpiochip->irq.chip;
	const struct irq_domain_ops *ops;
	struct device_node *np;
	unsigned int type;
	unsigned int i;
......
	np = gpiochip->gpiodev->dev.of_node;
	type = gpiochip->irq.default_type;		//默认触发类型
.....
	gpiochip->to_irq = gpiochip_to_irq;   /*驱动request irq时调用*/
	gpiochip->irq.default_type = type;
	gpiochip->irq.lock_key = lock_key;
	gpiochip->irq.request_key = request_key;

	if (gpiochip->irq.domain_ops)
		ops = gpiochip->irq.domain_ops;
	else
		ops = &gpiochip_domain_ops;

    /* 创建一个linear irq domain，从这里看到，每一个bank都会有一个irq domain，ngpio是这个bank含有的gpio的个数，也是这个irq domain支持的中断的个数*/
	gpiochip->irq.domain = irq_domain_add_simple(np, gpiochip->ngpio,
						     gpiochip->irq.first,
						     ops, gpiochip);
	......
	return 0;
}

static const struct irq_domain_ops gpiochip_domain_ops = {
	.map	= gpiochip_irq_map,
	.unmap	= gpiochip_irq_unmap,
	/* Virtually all GPIO irqchips are twocell:ed */
	.xlate	= irq_domain_xlate_twocell,
};

ret = devm_request_irq(bank->chip.parent, bank->irq,
			       omap_gpio_irq_handler,
			       0, dev_name(bank->chip.parent), bank);