Linux驱动开发十一：分层分离LED子系统

本例根据韦东山视频第二期的第14课



分层分离而来，用QT6410实践

本例为点亮LED：

最简单的led驱动就是从端口输出0或1来关闭或点亮灯。而我们这里讲的led子系统，主要是对led事件进行了分装和优化，这里我们主要讲的是可以实现跨平台的led驱动。不管你是使用三星的平台，还是Atmel的平台，你只要知道如何在你的BSP中添加平台数据，并且知道如何在应用程序中使用这个驱动，那么你就不用因为新的平台而再次编写led驱动。

代码如下：

led_dev.c

#include <linux/module.h>#include <linux/version.h>#include <linux/init.h>#include <linux/kernel.h>#include <linux/types.h>#include <linux/interrupt.h>#include <linux/list.h>#include <linux/timer.h>#include <linux/init.h>#include <linux/serial_core.h>#include <linux/platform_device.h>/* 分配/设置/注册一个platform_device */static struct resource led_resource[] = {    [0] = {        .start = 0x7F008820,        .end   = 0x7F008820 + 16 - 1,        .flags = IORESOURCE_MEM,    },    [1] = {        .start = 0,        .end   = 0,        .flags = IORESOURCE_IRQ,    }};static void led_release(struct device * dev){}static struct platform_device led_dev = {    .name         = "myled",    .id       = -1,    .num_resources    = ARRAY_SIZE(led_resource),    .resource     = led_resource,    .dev = {     .release = led_release, },};static int led_dev_init(void){platform_device_register(&led_dev);return 0;}static void led_dev_exit(void){platform_device_unregister(&led_dev);}module_init(led_dev_init);module_exit(led_dev_exit);MODULE_LICENSE("GPL");

led_drv.c

/* 分配/设置/注册一个platform_driver */#include <linux/module.h>#include <linux/version.h>#include <linux/init.h>#include <linux/fs.h>#include <linux/interrupt.h>#include <linux/irq.h>#include <linux/sched.h>#include <linux/pm.h>#include <linux/sysctl.h>#include <linux/proc_fs.h>#include <linux/delay.h>#include <linux/platform_device.h>#include <linux/input.h>#include <linux/irq.h>#include <asm/uaccess.h>#include <asm/io.h>static int major;static struct class *cls;static struct class_device *led_cls;static volatile unsigned long *gpio_con;static volatile unsigned long *gpio_dat;static int pin;static int led_open(struct inode *inode, struct file *file){//printk("first_drv_open\n");/* 配置为输出 */*gpio_con &= ~(0xf<<(pin*4));*gpio_con |= (0x1<<(pin*4));return 0;}static ssize_t led_write(struct file *file, const char __user *buf, size_t count, loff_t * ppos){int val;//printk("first_drv_write\n");copy_from_user(&val, buf, count); //copy_to_user();if (val == 1){// 点灯*gpio_dat &= ~(1<<pin);}else{// 灭灯*gpio_dat |= (1<<pin);}return 0;}static struct file_operations led_fops = {    .owner  =   THIS_MODULE,    /* 这是一个宏，推向编译模块时自动创建的__this_module变量 */    .open   =   led_open,     .write=led_write,   };static int led_probe(struct platform_device *pdev){struct resource*res;/* 根据platform_device的资源进行ioremap */res = platform_get_resource(pdev, IORESOURCE_MEM, 0);gpio_con = ioremap(res->start, res->end - res->start + 1);gpio_dat = gpio_con + 1;res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);pin = res->start;/* 注册字符设备驱动程序 */printk("led_probe, found led\n");major = register_chrdev(0, "myled", &led_fops);cls = class_create(THIS_MODULE, "myled");led_cls = device_create(cls, NULL, MKDEV(major, 0), NULL, "led"); /* /dev/led */return 0;}static int led_remove(struct platform_device *pdev){/* 卸载字符设备驱动程序 *//* iounmap */printk("led_remove, remove led\n");device_unregister(led_cls);class_destroy(cls);unregister_chrdev(major, "myled");iounmap(gpio_con);return 0;}struct platform_driver led_drv = {.probe= led_probe,.remove= led_remove,.driver= {.name= "myled",}};static int led_drv_init(void){platform_driver_register(&led_drv);return 0;}static void led_drv_exit(void){platform_driver_unregister(&led_drv);}module_init(led_drv_init);module_exit(led_drv_exit);MODULE_LICENSE("GPL");

Makefile:

KERN_DIR = /work/work/linuxall:make -C $(KERN_DIR) M=`pwd` modules cp *.ko /work/nfsrootclean:make -C $(KERN_DIR) M=`pwd` modules cleanobj-m+= led_drv.oobj-m+= led_dev.o

led_test.c

#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>/* led_test on * led_test off */int main(int argc, char **argv){int fd;int val = 1;fd = open("/dev/led", O_RDWR);if (fd < 0){printf("can't open!\n");}if (argc != 2){printf("Usage :\n");printf("%s <on|off>\n", argv[0]);return 0;}if (strcmp(argv[1], "on") == 0){val  = 1;}else{val = 0;}write(fd, &val, 4);return 0;}

执行

 ./led_test on

时点亮第一盏灯；

执行

 ./led_test off

时熄灭第一盏灯；