Linux驱动GPIO中断

监听GPIO引脚变化是嵌入式开发的基础知识。在Linux驱动中监听GPIO电平变化也是很方便的。下面的例子就演示了如何监听GPIO引脚电平变化？

实验环境

raspberry pi3b

Linux raspberrypi 6.1.21-v8+ #1642 SMP PREEMPT Mon Apr  3 17:24:16 BST 2023 aarch64 GNU/Linux

驱动代码

// simple.c

#include <linux/gpio.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>

static unsigned int irq_number = 0;

static irqreturn_t gpio_irq_handler(int irq, void *dev_id) {
    pr_info("simple_gpio_irq_handler\n");
    return (irqreturn_t)IRQ_HANDLED;
}

static int __init simple_init(void) {
    pr_info("simple_init\n");

    if (gpio_request(17, "rpi-gpio-17")) {
        pr_err("gpio_request 17 error\n");
        return -1;
    }

    if (gpio_direction_input(17)) {
        pr_err("gpio_direction_input 17 error\n");
        return -1;
    }

    irq_number = gpio_to_irq(17);

    if (request_irq(irq_number, (irq_handler_t)gpio_irq_handler,
                    IRQF_TRIGGER_RISING, "my_gpio_irq", NULL) != 0) {
        pr_err("request_irq 17 error\n");
        gpio_free(17);
        return -1;
    }

    return 0;
}

static void __exit simple_exit(void) {
    pr_info("simple_exit\n");
    free_irq(irq_number, NULL);
    gpio_free(17);
}

module_init(simple_init);
module_exit(simple_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("heng30");
MODULE_VERSION("v0.0.1");
MODULE_DESCRIPTION("A simple kernel module");

Makefile编译脚本

#!/bin/sh

top-dir = $(shell pwd)
kernel-version = $(shell uname -r)
kernel-dir ?= /lib/modules/$(kernel-version)/build

obj-m += simple.o

all:
        make -C $(kernel-dir) modules M=$(top-dir)

clean:
        rm -f *.o *.ko *.mod *.mod.c *.order *.symvers *.dtbo
        make -C $(kernel-dir) clean m=$(top-dir)

测试

• 安装gpio工具：sudo apt install gpiod

• 查看gpio设备：gpiodetect

gpiochip0 [pinctrl-bcm2835] (54 lines)
gpiochip1 [raspberrypi-exp-gpio] (8 lines)

• 编译程序：make

• 安装驱动：insmod simple.ko

• 查看中断：cat /proc/interrupts

           CPU0       CPU1       CPU2       CPU3
...
184:          0          0          0          0  pinctrl-bcm2835  17 Edge      my_gpio_irq
...

• 移除驱动：rmmod simple.ko

• 查看输出：dmesg

参考

• 树莓派引脚图