嵌入式linux字符设备驱动--LED驱动编写

linux内核编程主要就是驱动 驱动分为字符设备、块设备、网络设备 驱动的编写就是将原来嵌入式操作寄存器的函数按照linux的驱动框架填进去

芯片：野火imx6ull linux版本4.15

led.c

#include <linux/types.h> #include <linux/kernel.h> #include <linux/delay.h> #include <linux/ide.h> #include <linux/init.h> #include <linux/module.h> #include <linux/errno.h> #include <linux/gpio.h> #include <asm/mach/map.h> #include <asm/uaccess.h> #include <asm/io.h> #include <linux/cdev.h> #include <linux/device.h> /* 寄存器物理地址 */ #define CCM_CCGR1_BASE (0X020C406C) #define SW_MUX_GPIO1_IO03_BASE (0X020E0068) #define SW_PAD_GPIO1_IO03_BASE (0X020E02F4) #define GPIO1_DR_BASE (0X0209C000) #define GPIO1_GDIR_BASE (0X0209C004) /* 映射后的寄存器虚拟地址指针 */ static void __iomem *IMX6U_CCM_CCGR1; static void __iomem *SW_MUX_GPIO1_IO03; static void __iomem *SW_PAD_GPIO1_IO03; static void __iomem *GPIO1_DR; static void __iomem *GPIO1_GDIR; #define LED_CNT 1 /* 设备号个数 */ #define LED_NAME "myled" /* 名字 */ /* led 设备结构体 */ struct led_dev{ dev_t devid; /* 设备号 */ struct cdev cdev; /* cdev */ struct class *class; /* 类 */ struct device *device; /* 设备 */ int major; /* 主设备号 */ int minor; /* 次设备号 */ }; struct led_dev led; /* led 设备 */ static void led_gpio_config(void) { u32 val = 0; /* 初始化 LED */ /* 1、寄存器地址映射 */ IMX6U_CCM_CCGR1 = ioremap(CCM_CCGR1_BASE, 4); SW_MUX_GPIO1_IO03 = ioremap(SW_MUX_GPIO1_IO03_BASE, 4); SW_PAD_GPIO1_IO03 = ioremap(SW_PAD_GPIO1_IO03_BASE, 4); GPIO1_DR = ioremap(GPIO1_DR_BASE, 4); GPIO1_GDIR = ioremap(GPIO1_GDIR_BASE, 4); /* 2、使能 GPIO1 时钟 */ val = readl(IMX6U_CCM_CCGR1); val &= ~(3 << 26); /* 清除以前的设置 */ val |= (3 << 26); /* 设置新值 */ writel(val, IMX6U_CCM_CCGR1); /* 3、设置 GPIO1_IO03 的复用功能，将其复用为 * GPIO1_IO03，最后设置 IO 属性。 */ writel(5, SW_MUX_GPIO1_IO03); /* 寄存器 SW_PAD_GPIO1_IO03 设置 IO 属性 */ writel(0x10B0, SW_PAD_GPIO1_IO03); /* 4、设置 GPIO1_IO03 为输出功能 */ val = readl(GPIO1_GDIR); val &= ~(1 << 3); /* 清除以前的设置 */ val |= (1 << 3); /* 设置为输出 */ writel(val, GPIO1_GDIR); /* 5、默认关闭 LED */ val = readl(GPIO1_DR); val |= (1 << 3); writel(val, GPIO1_DR); } static void led_sw(unsigned char x) { unsigned long tmp = 0; if(x == '1') { tmp = readl(GPIO1_DR); tmp |= (1 << 3); writel(tmp, GPIO1_DR); } else if(x == '0') { tmp = readl(GPIO1_DR); tmp &= ~(1 << 3); writel(tmp, GPIO1_DR); } } static int led_open (struct inode * inode, struct file * file) { printk(" device open\n"); file->private_data = &led; /* 设置私有数据 */ return 0; } static int led_release (struct inode * inode, struct file * file) { printk(" device release\n"); return 0; } ssize_t led_read (struct file *filp, char __user * buf, size_t count, loff_t *ppos) { printk(" device read\n"); return 0; } ssize_t led_write (struct file *filp, const char __user * buf, size_t cnt, loff_t *ppos) { int retvalue; unsigned char databuf[1]; unsigned char ledstat; retvalue = copy_from_user(databuf, buf, cnt); if(retvalue < 0) { printk("kernel write failed!\r\n"); return -EFAULT; } ledstat = databuf[0]; /* 获取状态值 */ if(ledstat == '1') { led_sw('1'); /* 打开 LED 灯 */} else if(ledstat == '0') {led_sw('0'); /* 关闭 LED 灯 */} printk(" device write\n"); return 0; } /* 设备操作函数 */ static struct file_operations led_fops = { .owner = THIS_MODULE, .open = led_open, .read = led_read, .write = led_write, .release = led_release, }; static int __init led_init(void) { led_gpio_config(); /* 1、创建设备号 */ if (led.major) { /* 定义了设备号 */ led.devid = MKDEV(led.major, 0); register_chrdev_region(led.devid, LED_CNT, LED_NAME); } else { /* 没有定义设备号 */ alloc_chrdev_region(&led.devid, 0, LED_CNT,LED_NAME); /* 申请设备号 */ led.major = MAJOR(led.devid); /* 获取主设备号 */ led.minor = MINOR(led.devid); /* 获取次设备号 */ } printk("newcheled major=%d,minor=%d\r\n",led.major,led.minor); /* 2、初始化 cdev */ led.cdev.owner = THIS_MODULE; cdev_init(&led.cdev, &led_fops); /* 3、添加一个 cdev */ cdev_add(&led.cdev, led.devid, LED_CNT); /* 4、创建类 */ led.class = class_create(THIS_MODULE, LED_NAME); if (IS_ERR(led.class)) { return PTR_ERR(led.class); } /* 5、创建设备 */ led.device = device_create(led.class, NULL, led.devid, NULL, LED_NAME); if (IS_ERR(led.device)) { return PTR_ERR(led.device); } printk(" device insmod ok\n"); return 0; } static void __exit led_exit(void) { /* 取消映射 */ iounmap(IMX6U_CCM_CCGR1); iounmap(SW_MUX_GPIO1_IO03); iounmap(SW_PAD_GPIO1_IO03); iounmap(GPIO1_DR); iounmap(GPIO1_GDIR); /* 注销字符设备 */ cdev_del(&led.cdev);/* 删除 cdev */ unregister_chrdev_region(led.devid, LED_CNT); device_destroy(led.class, led.devid); class_destroy(led.class); printk(" device rmmod ok\n"); } module_init(led_init); module_exit(led_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("guoguo");

Makefile

#内核源码树路径 KERN_DIR := /home/z/imax6ull/kernel ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- export ARCH CROSS_COMPILE #目标文件 obj-m += led.o all: $(MAKE) -C $(KERN_DIR) M=$(CURDIR) modules .PHONY:clean clean: #$(MAKE) -C $(KERNEL_DIR) M=$(CURDIR) clean rm -f *.o *.ko *.order *.symvers

led应用测试程序 ledtest.c

#include "stdio.h" #include "unistd.h" #include "sys/types.h" #include "sys/stat.h" #include "fcntl.h" #include "stdlib.h" #include "string.h" static int fd = 0; void led_init() { /* 打开 led 驱动 */ fd = open("/dev/myled", O_RDWR); if(fd < 0) { printf("file %s open failed!\r\n"); return -1; } } int led_set(unsigned char x) { int ret = 0; unsigned char buff[1]; if(x){buff[0] = '1';}else{buff[0] = '0';} ret = write(fd, buff, sizeof(buff)); if(ret < 0) { printf("LED Control Failed!\r\n"); close(fd); return -1; } } int main() { led_init(); while(1) { led_set(1); sleep(1); led_set(0); sleep(1); } close(fd); /* 关闭文件 */ return 0; }

编译驱动 make 会在当前目录生成led.ko

编译应用程序 arm-linux-gnueabihf-gcc ledtest.c-o ledtest

加载驱动 insmod led.ko 运行应用测试 ./ledtest