视频：第11讲 Linux按键输入试验_哔哩哔哩_bilibili
本实验是直接读取io数据。使用中断等方式进行按键输入的方式放在以后了。
1. 设备树
（详见正点原子\02、开发板原理图\02、开发板原理图\IMX6ULL_ALPHA_V2.1(底板原理图).pdf）
开发板上的KEY0对应UART1_CTS。且按下为低电平。
1.1 pinctrl
首先配置pinctrl。我们将其复用为一个普通的GPIO。可以在imx6ull-pinfunc.h中找到复用：
#define MX6UL_PAD_UART1_CTS_B__GPIO1_IO18 0x008C 0x0318 0x0000 0x5 0x0将UART1_CTS复用为GPIO1_IO18，并将电器属性配置为0xF080（具体可以看《IMX6ULL参考手册》）：
cpp
// 写到imx6ull-alientek-emmc.dts里的&iomuxc下
pinctrl_key: keygrp{
fsl,pins = <
MX6UL_PAD_UART1_CTS_B__GPIO1_IO18 0xF080
>;
};
1.2 gpio
cpp
// 写到imx6ull-alientek-emmc.dts里根节点的最后
key{
compatible = "alientek,key";
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_key>;
key-gpios = <&gpio1 18 GPIO_ACTIVE_HIGH>; // GPIO1_pin18 高电平有效。不过作为输入这个有效电平其实没有意义
status = "okay";
};
1.3 编译
cpp
# VSCODE终端
make dtbs
sudo cp arch/arm/boot/dts/imx6ull-alientek-emmc.dtb /..../tftpboot/ -f
# 串口
cd proc/device-tree/
ls # 此时应当能找到key节点
2.1 文件结构
cpp
10_KEY (工作区)
├── .vscode
│ ├── c_cpp_properties.json
│ └── settings.json
├── 10_key.code-workspace
├── Makefile
├── keyAPP.c
└── key.c2.2 Makefile
bash
CFLAGS_MODULE += -w
KERNELDIR := /home/for/linux/imx6ull/linux/linux-imx-rel_imx_4.1.15_2.1.0_ga_alientek # 内核路径
# KERNELDIR改成自己的 linux-imx-rel_imx_4.1.15_2.1.0_ga_alientek文件路径（这个文件从正点原子"01、例程源码"中直接搜，cp到虚拟机里面）
CURRENT_PATH := $(shell pwd) # 当前路径
obj-m := key.o # 编译文件
build: kernel_modules # 编译模块
kernel_modules:
$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) modules
clean:
$(MAKE) -C $(KERNELDIR) M=$(CURRENT_PATH) clean 2.3 key.c
cpp
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/io.h>
#include <linux/cdev.h>
#include <linux/kdev_t.h>
#include <linux/stat.h>
#include <linux/device.h>
#include <linux/of_gpio.h>
#include <linux/atomic.h>
#define KEY_NAME "key"
#define KEY_CNT 1
#define KEY0VALUE 0XFF // 有效
#define INVAKEY 0X00 // 无效
/* 设备结构体 */
struct key_dev{
dev_t devid;
int major;
int minor;
struct cdev cdev;
struct device *device;
struct class *class;
struct device_node *nd;
int key_gpio;
atomic_t keyvalue;
};
struct key_dev key;
/* 操作集 */
static int key_release(struct inode *inode, struct file *filp){
struct key_dev *dev = filp->private_data;
return 0;
}
static int key_open(struct inode *inode, struct file *filp){
filp->private_data = &key;
return 0;
}
static ssize_t key_write(struct file *filp, const char __user *buf, size_t count, loff_t *ppos){
int ret;
return 0;
}
static ssize_t key_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos){
int value;
struct key_dev *dev = filp->private_data;
int ret = 0;
if(gpio_get_value(dev->key_gpio) == 0){ /* 低电平->按下*/
while(!gpio_get_value(dev->key_gpio)); /* 等待释放 */
atomic_set(&dev->keyvalue, KEY0VALUE);
} else {
atomic_set(&dev->keyvalue, INVAKEY);
}
value = atomic_read(&dev->keyvalue);
ret = copy_to_user(buf, &value, sizeof(value));
return 0;
}
static const struct file_operations key_fops = {
.owner = THIS_MODULE,
.write = key_write,
.open = key_open,
.release = key_release,
.read = key_read,
};
/* key 初始化*/
static int keyio_init(struct key_dev* dev){
int ret = 0;
/* 初始化 keyvalue*/
atomic_set(&key.keyvalue, INVAKEY);
/* 1.获取设备节点 */
dev->nd = of_find_node_by_path("/key");
if(dev->nd == NULL){
ret = -EINVAL;
goto fail_nd;
}
/* 2.获取LED对应的GPIO */ // 也就是节点中led-gpios那一行内容
dev->key_gpio = of_get_named_gpio(dev->nd, "key-gpios", 0);
if(dev->key_gpio < 0){
ret = -EINVAL;
goto fail_gpio;
}
/* 3.申请IO */
ret = gpio_request(dev->key_gpio, "key0");
if(ret){
ret = -EBUSY;
printk("IO %d has been used!\r\n",dev->key_gpio);
goto fail_request;
}
/* 4.使用IO，设置为输入 */
ret = gpio_direction_input(dev->key_gpio);
if(ret < 0){
ret = -EINVAL;
goto fail_input;
}
return 0;
fail_input: // 如果执行到这一步，说明已经gpio_request成功了，因此需要释放gpio
gpio_free(dev->key_gpio);
fail_request:
fail_gpio:
fail_nd:
return ret;
}
/* 驱动入口 */
static int __init key_init(void){
int ret = 0;
/* 1.注册字符设备驱动 */
key.devid = 0;
if(key.devid){
key.devid = MKDEV(key.devid, 0);
register_chrdev_region(key.devid, KEY_CNT, KEY_NAME);
} else {
alloc_chrdev_region(&key.devid, 0, KEY_CNT, KEY_NAME);
key.major = MAJOR(key.devid);
key.minor = MINOR(key.devid);
}
/* 2.初始化cdev */
key.cdev.owner = THIS_MODULE;
cdev_init(&key.cdev, &key_fops);
/* 3.添加cdev */
cdev_add(&key.cdev, key.devid, KEY_CNT); // 错误处理先略过了
/* 4.创建类 */
key.class = class_create(THIS_MODULE, KEY_NAME);
if(IS_ERR(key.class)){
return PTR_ERR(key.class);
}
/* 5.创建设备 */
key.device = device_create(key.class, NULL, key.devid, NULL, KEY_NAME);
if(IS_ERR(key.device)){
return PTR_ERR(key.device);
}
ret = keyio_init(&key);
if(ret < 0){goto fail_device;}
return 0;
fail_device:
class_destroy(key.class);
return ret;
}
/* 驱动出口 */
static void __exit key_exit(void){
/* 注销字符设备驱动 */
cdev_del(&key.cdev);
unregister_chrdev_region(key.devid, KEY_CNT);
device_destroy(key.class, key.devid);
class_destroy(key.class);
gpio_free(key.key_gpio);
}
module_init(key_init);
module_exit(key_exit);
MODULE_LICENSE("GPL");2.4 keyAPP.c
cpp
#include<stdio.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
#include<stdlib.h>
#include<string.h>
/*
* @description : main主程序
* @param - argc : argv数组元素个数
* @param - argv : 具体参数
* @return : 0 成功; else失败
* 调用 ./keyAPP /dev/key
*/
#define KEY0VALUE 0XFF // 有效
#define INVAKEY 0X00 // 无效
int main(int argc, char *argv[]){
if(argc != 2){ // 判断用法是否错误
printf("Error Usage!\r\n");
return -1;
}
char *filename;
int fd = 0;
unsigned char databuf[1];
int retvalue = 0;
int cnt = 0;
int value;
filename = argv[1];
fd = open(filename, O_RDWR); // 读写模式打开驱动文件filename
if(fd <0){
printf("file %s open failed!\r\n");
return -1;
}
while(1){
read(fd, &value, sizeof(value));
if(value == KEY0VALUE){
printf("KEY0 Press\r\n");
}
}
close(fd);
return 0;
}2.5 测试
bash
# VSCODE
make
arm-linux-gnueabihf-gcc keyAPP.c -o keyAPP
sudo cp keyAPP key.ko /..../nfs/rootfs/lib/modules/4.1.15/ -f
# 串口
cd /lib/modules/4.1.15/
depmod
modprobe key.ko
./keyAPP /dev/key
# 此时按一次key0，输出一行"KEY0 Press"