我尝试在自定义平台上首次设置设备树源文件。板上是恩智浦PCA9555 gpio扩展器。我试图为设备设置节点并且有点困惑。
以下是我在dts文件中使用节点的地方：
ioexp0: gpio-exp@21 {
compatible = "nxp,pca9555";
reg = <21>;
interrupt-parent = <&gpio>;
interrupts = <8 0>;
gpio-controller;
#gpio-cells = <2>;
/*I don't understand the following two lines*/
interrupt-controller;
#interrupt-cells = <2>;
};
我通过使用armada-388-gp.dts来源作为指导来达到这一点。
我的困惑在于什么代码处理#interrupt-cells属性。 bindings documentation对于这个芯片来说根本不是很有帮助，因为它没有说明关于中断单元解释的任何内容。
查看pca9555驱动程序source code中的pca953x_irq_setup函数 - 我无法看到处理#interrupt-cells属性的任何地方。这是在linux中断处理代码中处理的吗？我只是想知道如何知道两个中断单元的含义。
pca953x_irq_setup：
static int pca953x_irq_setup(struct pca953x_chip *chip,
int irq_base)
{
struct i2c_client *client = chip->client;
int ret, i;
if (client->irq && irq_base != -1
&& (chip->driver_data & PCA_INT)) {
ret = pca953x_read_regs(chip,
chip->regs->input, chip->irq_stat);
if (ret)
return ret;
/*
* There is no way to know which GPIO line generated the
* interrupt. We have to rely on the previous read for
* this purpose.
*/
for (i = 0; i < NBANK(chip); i++)
chip->irq_stat[i] &= chip->reg_direction[i];
mutex_init(&chip->irq_lock);
ret = devm_request_threaded_irq(&client->dev,
client->irq,
NULL,
pca953x_irq_handler,
IRQF_TRIGGER_LOW | IRQF_ONESHOT |
IRQF_SHARED,
dev_name(&client->dev), chip);
if (ret) {
dev_err(&client->dev, "failed to request irq %d\n",
client->irq);
return ret;
}
ret = gpiochip_irqchip_add_nested(&chip->gpio_chip,
&pca953x_irq_chip,
irq_base,
handle_simple_irq,
IRQ_TYPE_NONE);
if (ret) {
dev_err(&client->dev,
"could not connect irqchip to gpiochip\n");
return ret;
}
gpiochip_set_nested_irqchip(&chip->gpio_chip,
&pca953x_irq_chip,
client->irq);
}
return 0;
}
这是我第一次使用设备树，所以我希望它显而易见，我只是缺席。
答案 0 :(得分：1)
在查看了所有评论后，我做了一些额外的阅读，并找到了答案。
我现在明白我误解了设备树的一些属性。我之前的印象是驱动程序必须指定所有属性的处理方式。我现在看到linux实际上会处理许多通用属性，例如gpios或interrupts（这很有意义）。
实际interrupts binding的文档非常有用，而不是设备驱动程序的文档。
以下是对从intspec到IRQ_TYPE*的转换如何发生的详细说明：
函数of_irq_parse_one将中断说明符整数复制到struct of_phandle_args here。然后通过消费者函数（例如irq_create_of_mapping）将此arg传递给of_irq_get。然后，此函数将这些参数通过struct irq_fwspec映射到of_phandle_args_to_fwspec，并将其fwspec数据传递给irq_create_fwspec_mapping。这些功能都在irqdomain.c中找到。此时，irq将属于irq_domain或使用irq_default_domain。据我所知 - pca853x驱动程序使用默认域。此域通常由特定于平台的代码设置。我通过搜索irq_domain_ops on cross reference找到了我的。其中很多似乎只是通过intspec[1] & IRQ_TYPE_SENSE_MASK将type简单地复制到irq_create_fwspec_mapping中的irq_domain_translate变量。从这里开始，类型通过irq_data设置为irq的irqd_set_trigger_type。
of_irq_parse_one：
/**
* of_irq_parse_one - Resolve an interrupt for a device
* @device: the device whose interrupt is to be resolved
* @index: index of the interrupt to resolve
* @out_irq: structure of_irq filled by this function
*
* This function resolves an interrupt for a node by walking the interrupt tree,
* finding which interrupt controller node it is attached to, and returning the
* interrupt specifier that can be used to retrieve a Linux IRQ number.
*/
int of_irq_parse_one(struct device_node *device, int index, struct of_phandle_args *out_irq)
{
struct device_node *p;
const __be32 *intspec, *tmp, *addr;
u32 intsize, intlen;
int i, res;
pr_debug("of_irq_parse_one: dev=%s, index=%d\n", of_node_full_name(device), index);
/* OldWorld mac stuff is "special", handle out of line */
if (of_irq_workarounds & OF_IMAP_OLDWORLD_MAC)
return of_irq_parse_oldworld(device, index, out_irq);
/* Get the reg property (if any) */
addr = of_get_property(device, "reg", NULL);
/* Try the new-style interrupts-extended first */
res = of_parse_phandle_with_args(device, "interrupts-extended",
"#interrupt-cells", index, out_irq);
if (!res)
return of_irq_parse_raw(addr, out_irq);
/* Get the interrupts property */
intspec = of_get_property(device, "interrupts", &intlen);
if (intspec == NULL)
return -EINVAL;
intlen /= sizeof(*intspec);
pr_debug(" intspec=%d intlen=%d\n", be32_to_cpup(intspec), intlen);
/* Look for the interrupt parent. */
p = of_irq_find_parent(device);
if (p == NULL)
return -EINVAL;
/* Get size of interrupt specifier */
tmp = of_get_property(p, "#interrupt-cells", NULL);
if (tmp == NULL) {
res = -EINVAL;
goto out;
}
intsize = be32_to_cpu(*tmp);
pr_debug(" intsize=%d intlen=%d\n", intsize, intlen);
/* Check index */
if ((index + 1) * intsize > intlen) {
res = -EINVAL;
goto out;
}
/* Copy intspec into irq structure */
intspec += index * intsize;
out_irq->np = p;
out_irq->args_count = intsize;
for (i = 0; i < intsize; i++)
out_irq->args[i] = be32_to_cpup(intspec++);
/* Check if there are any interrupt-map translations to process */
res = of_irq_parse_raw(addr, out_irq);
out:
of_node_put(p);
return res;
}
EXPORT_SYMBOL_GPL(of_irq_parse_one)
irq_create_fwspec_mapping：
unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
{
struct irq_domain *domain;
struct irq_data *irq_data;
irq_hw_number_t hwirq;
unsigned int type = IRQ_TYPE_NONE;
int virq;
if (fwspec->fwnode) {
domain = irq_find_matching_fwspec(fwspec, DOMAIN_BUS_WIRED);
if (!domain)
domain = irq_find_matching_fwspec(fwspec, DOMAIN_BUS_ANY);
} else {
domain = irq_default_domain;
}
if (!domain) {
pr_warn("no irq domain found for %s !\n",
of_node_full_name(to_of_node(fwspec->fwnode)));
return 0;
}
if (irq_domain_translate(domain, fwspec, &hwirq, &type))
return 0;
/*
* WARN if the irqchip returns a type with bits
* outside the sense mask set and clear these bits.
*/
if (WARN_ON(type & ~IRQ_TYPE_SENSE_MASK))
type &= IRQ_TYPE_SENSE_MASK;
/*
* If we've already configured this interrupt,
* don't do it again, or hell will break loose.
*/
virq = irq_find_mapping(domain, hwirq);
if (virq) {
/*
* If the trigger type is not specified or matches the
* current trigger type then we are done so return the
* interrupt number.
*/
if (type == IRQ_TYPE_NONE || type == irq_get_trigger_type(virq))
return virq;
/*
* If the trigger type has not been set yet, then set
* it now and return the interrupt number.
*/
if (irq_get_trigger_type(virq) == IRQ_TYPE_NONE) {
irq_data = irq_get_irq_data(virq);
if (!irq_data)
return 0;
irqd_set_trigger_type(irq_data, type);
return virq;
}
pr_warn("type mismatch, failed to map hwirq-%lu for %s!\n",
hwirq, of_node_full_name(to_of_node(fwspec->fwnode)));
return 0;
}
if (irq_domain_is_hierarchy(domain)) {
virq = irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, fwspec);
if (virq <= 0)
return 0;
} else {
/* Create mapping */
virq = irq_create_mapping(domain, hwirq);
if (!virq)
return virq;
}
irq_data = irq_get_irq_data(virq);
if (!irq_data) {
if (irq_domain_is_hierarchy(domain))
irq_domain_free_irqs(virq, 1);
else
irq_dispose_mapping(virq);
return 0;
}
/* Store trigger type */
irqd_set_trigger_type(irq_data, type);
return virq;
}
EXPORT_SYMBOL_GPL(irq_create_fwspec_mapping);