实验过程

实验目的： 在龙芯开发板上面验证GPIO按键的输入过程

① 根据原理图连接按键板

② 将4个i2c引脚的功能复用为GPIO

③ 注册input设备驱动，绑定中断处理函数，使用定时器消抖

原理图

4个按键引脚：CPU_I2C0_SCL -> GPIO48, CPU_I2C0_SDA -> GPIO49, CPU_I2C1_SCL -> GPIO50, CPU_I2C1_SDA -> GPIO51

实物连接图：按顺序连接好按键板上面的K1、K2、K3、K4、GND

设备树

还是把i2c0和i2c1部分代码注释掉，需要把它们当作4个GPIO来使用

驱动程序

GPIO、中断和KEY的对应关系表

GPIO	中断	KEY	引脚
48	25	①	16
49	26	②	18
50	27	③	15
51	28	④	17

定义相关按键设备结构体

#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/input.h>

#define KEY_INPUT	"key_input"
#define KEY_NUM	4

struct my_key_dev{
	struct input_dev *idev;
	struct timer_list timer;
	int key[KEY_NUM];
	int irq[KEY_NUM];	
	int index;	
};

struct my_key_dev key_dev;	

GPIO按键初始化

static int __init gpio_key_init(void)
{
	int ret = 0;
	int i = 0;
	
	// timer
	timer_setup(&key_dev.timer, key_timer_function, 0);

	for(i = 0; i < KEY_NUM; i++) {
		// gpio 48 49 50 51
		key_dev.key[i] = 48 + i;

		// request
		ret = gpio_request(key_dev.key[i], "LED-GPIO");
		if (ret) {
			printk(KERN_ERR "key_dev: Failed to request led-gpio\n");
			return ret;
		}

		// input
		ret = gpio_direction_input(key_dev.key[i]);
		if(ret < 0) {
			printk("can't set gpio!\r\n");
		}

		// irq
		key_dev.irq[i] = gpio_to_irq(key_dev.key[i]); 
		printk("key%d -> irq : %d\n", key_dev.key[i], key_dev.irq[i]);
		if(i == 0) {
			ret = request_irq(key_dev.irq[i], key_interrupt0, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key0_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 1) {
			ret = request_irq(key_dev.irq[i], key_interrupt1, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key1_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 2) {
			ret = request_irq(key_dev.irq[i], key_interrupt2, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key2_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 3) {
			ret = request_irq(key_dev.irq[i], key_interrupt3, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key3_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
	}

	// input dev
	key_dev.idev = input_allocate_device();
	key_dev.idev->name = KEY_INPUT;
	key_dev.idev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
	input_set_capability(key_dev.idev, EV_KEY, KEY_LEFT | KEY_RIGHT | KEY_UP | KEY_DOWN);
	ret = input_register_device(key_dev.idev);
	if (ret) {
		printk("register input device failed!\r\n");
		goto free_gpio;
	}

	return ret;

free_gpio:
	for(i = 0; i < KEY_NUM; i++) {
		free_irq(key_dev.irq[i],NULL);
		gpio_free(key_dev.key[i]);
		
	}

	del_timer_sync(&key_dev.timer);
	return -EIO;
}

中断处理

static irqreturn_t key_interrupt0(int irq, void *dev_id)
{
	// printk("key_interrupt0 irq %d \n", irq);
	if(irq == key_dev.irq[0]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 0;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt1(int irq, void *dev_id)
{
	// printk("key_interrupt1 irq %d \n", irq);
	if(irq == key_dev.irq[1]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 1;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt2(int irq, void *dev_id)
{
	// printk("key_interrupt2 irq %d \n", irq);
	if(irq == key_dev.irq[2]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 2;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt3(int irq, void *dev_id)
{
	// printk("key_interrupt3 irq %d \n", irq);
	if(irq == key_dev.irq[3]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 3;
	}
    return IRQ_HANDLED;
}

定时器消抖

int key_array[] = {KEY_LEFT, KEY_RIGHT, KEY_UP, KEY_DOWN};

static void key_timer_function(struct timer_list *arg)
{
	int val = gpio_get_value(key_dev.key[key_dev.index]);
	printk("key_timer_function %d -> %d\n", key_dev.key[key_dev.index], val);
	// if(val == 0) {
		input_report_key(key_dev.idev, key_array[key_dev.index], !val);
		input_sync(key_dev.idev);

		// input_report_key(key_dev.idev, key_array[key_dev.index], 0);
		// input_sync(key_dev.idev);
		// printk("key %d press %d\n", key_dev.key[key_dev.index], key_array[key_dev.index]);
	// }
}

驱动模块卸载函数：回收相关的设备资源，如GPIO、中断、定时器等

static void __exit gpio_key_exit(void)
{
	int i;
	for(i = 0; i < KEY_NUM; i++) {
		free_irq(key_dev.irq[i],NULL);
		gpio_free(key_dev.key[i]);
	}

	del_timer_sync(&key_dev.timer);
	input_unregister_device(key_dev.idev);	
}

整合代码

#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/input.h>

#define KEY_INPUT	"key_input"
#define KEY_NUM	4

struct my_key_dev{
	struct input_dev *idev;
	struct timer_list timer;
	int key[KEY_NUM];
	int irq[KEY_NUM];	
	int index;	
};

struct my_key_dev key_dev;	

int key_array[] = {KEY_LEFT, KEY_RIGHT, KEY_UP, KEY_DOWN};

static void key_timer_function(struct timer_list *arg)
{
	int val = gpio_get_value(key_dev.key[key_dev.index]);
	printk("key_timer_function %d -> %d\n", key_dev.key[key_dev.index], val);
	// if(val == 0) {
		input_report_key(key_dev.idev, key_array[key_dev.index], !val);
		input_sync(key_dev.idev);

		// input_report_key(key_dev.idev, key_array[key_dev.index], 0);
		// input_sync(key_dev.idev);
		// printk("key %d press %d\n", key_dev.key[key_dev.index], key_array[key_dev.index]);
	// }
}

static irqreturn_t key_interrupt0(int irq, void *dev_id)
{
	// printk("key_interrupt0 irq %d \n", irq);
	if(irq == key_dev.irq[0]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 0;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt1(int irq, void *dev_id)
{
	// printk("key_interrupt1 irq %d \n", irq);
	if(irq == key_dev.irq[1]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 1;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt2(int irq, void *dev_id)
{
	// printk("key_interrupt2 irq %d \n", irq);
	if(irq == key_dev.irq[2]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 2;
	}
    return IRQ_HANDLED;
}

static irqreturn_t key_interrupt3(int irq, void *dev_id)
{
	// printk("key_interrupt3 irq %d \n", irq);
	if(irq == key_dev.irq[3]) {
		mod_timer(&key_dev.timer, jiffies + msecs_to_jiffies(15));
		key_dev.index = 3;
	}
    return IRQ_HANDLED;
}

static int __init gpio_key_init(void)
{
	int ret = 0;
	int i = 0;
    
    // timer
	timer_setup(&key_dev.timer, key_timer_function, 0);

	for(i = 0; i < KEY_NUM; i++) {
		// gpio 48 49 50 51
		key_dev.key[i] = 48 + i;

		// request
		ret = gpio_request(key_dev.key[i], "LED-GPIO");
		if (ret) {
			printk(KERN_ERR "key_dev: Failed to request led-gpio\n");
			return ret;
		}

		// input
		ret = gpio_direction_input(key_dev.key[i]);
		if(ret < 0) {
			printk("can't set gpio!\r\n");
		}

		// irq
		key_dev.irq[i] = gpio_to_irq(key_dev.key[i]); 
		printk("key%d -> irq : %d\n", key_dev.key[i], key_dev.irq[i]);
		if(i == 0) {
			ret = request_irq(key_dev.irq[i], key_interrupt0, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key0_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 1) {
			ret = request_irq(key_dev.irq[i], key_interrupt1, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key1_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 2) {
			ret = request_irq(key_dev.irq[i], key_interrupt2, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key2_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
		else if(i == 3) {
			ret = request_irq(key_dev.irq[i], key_interrupt3, IRQF_TRIGGER_FALLING | IRQF_TRIGGER_RISING, "Key3_IRQ", NULL);
			if (ret) {
				gpio_free(key_dev.key[i]);
				return ret;
			}
		}
	}

	// input dev
	key_dev.idev = input_allocate_device();
	key_dev.idev->name = KEY_INPUT;
	key_dev.idev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_REP);
	input_set_capability(key_dev.idev, EV_KEY, KEY_LEFT | KEY_RIGHT | KEY_UP | KEY_DOWN);
	ret = input_register_device(key_dev.idev);
	if (ret) {
		printk("register input device failed!\r\n");
		goto free_gpio;
	}

	return ret;

free_gpio:
	for(i = 0; i < KEY_NUM; i++) {
		free_irq(key_dev.irq[i],NULL);
		gpio_free(key_dev.key[i]);
		
	}

	del_timer_sync(&key_dev.timer);
	return -EIO;
}

static void __exit gpio_key_exit(void)
{
	int i;
	for(i = 0; i < KEY_NUM; i++) {
		free_irq(key_dev.irq[i],NULL);
		gpio_free(key_dev.key[i]);
	}

	del_timer_sync(&key_dev.timer);
	input_unregister_device(key_dev.idev);	
}

module_init(gpio_key_init);
module_exit(gpio_key_exit);
MODULE_LICENSE("GPL");

Makefile文件

obj-m += key.o 
KDIR:=/home/asensing/loongson/linux-4.19
ARCH=loongarch 
CROSS_COMPILE=loongarch64-linux-gnu-
PWD?=$(shell pwd) 
all:
	make -C $(KDIR) M=$(PWD) modules 

构建脚本

export PATH=$PATH:/home/asensing/loongson/loongson-gnu-toolchain-8.3-x86_64-loongarch64-linux-gnu-rc1.3-1/bin
make -j8
# loongarch64-linux-gnu-gcc test.c -o test
FILE=$PWD/$(basename $PWD).ko
scp $FILE root@192.168.137.11:/home/root

实验效果

插入驱动后，按下按键立即打印4个按键值