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三星6818LED驱动的编写

2022-07-21 17:26:00 【I＆You】

三星6818芯片基于linux的LED驱动详解

led驱动.c文件的编写

#PS:使用iowrite和ioread函数编写，没有用标准的gpio函数和ioctl函数会在下一篇超声波驱动介绍

  1. 一般驱动编写顺序是这样的
    1> 动态创建设备号
    2> 字符设备初始化
    3> 将设备添加到内核
    4> 创建设备
    5> 然后卸载驱动的时候记得释放资源就好
    附上代码：
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/device.h>
#include <linux/io.h>

static struct cdev gec6818_led_cdev;
//定义一个字符设备
static dev_t	led_num=0;
static struct class 	*leds_class;
//class是给udev管理设备用的
static struct device 	*leds_device;
//设备成功创建后的指针

static void __iomem		*gpioe_base_va;		//gpioe的虚拟地址基址
static void __iomem		*gpioe_out_va;		
static void __iomem		*gpioe_outenb_va;	
static void __iomem		*gpioe_altfn0_va;
static void __iomem		*gpioe_altfn1_va;	

static int  gec6818_led_open (struct inode * inode, struct file *file)
//打开驱动文件接口定义
{
    
	//配置GPIOE13为输出模式
	iowrite32(ioread32(gpioe_altfn0_va)&(~(3<<26)),gpioe_altfn0_va);
	//(这个操作可以参考之前那篇文章<三星6818基于uboot的流水灯程序>)
	//iowrite、ioread
	//1.从虚拟地址读取数据函数
	//#define ioread8(p) ({ unsigned int __v = __raw_readb(p); __v; })
	//#define ioread16(p) ({ unsigned int __v = le16_to_cpu((__force __le16)__raw_readw(p)); __v; })
	//#define ioread32(p) ({ unsigned int __v = le32_to_cpu((__force __le32)__raw_readl(p)); __v; })
	//2.向虚拟地址写入数据函数
	//#define iowrite8(v,p) __raw_writeb(v, p)
	//#define iowrite16(v,p) __raw_writew((__force __u16)cpu_to_le16(v), p)
	//#define iowrite32(v,p) __raw_writel((__force __u32)cpu_to_le32(v), p)
	
	//Linux 内核运行后，开启了 MMU（内存管理单元），所以不能直接访问 CPU 的物理地址，也就是说，不能直接使用物理地址访问系统的 IO 内存。必须将物理地址转换为虚拟地址，内核通过虚拟地址来访问系统的 IO 内存。
	iowrite32(ioread32(gpioe_outenb_va)|(1<<13),gpioe_outenb_va);	
		
	printk("gec6818_led_open \n");
	return 0;
}

static int  gec6818_led_release (struct inode * inode, struct file *file)
//释放接口定义
{
    
	printk("gec6818_led_release \n");
	return 0;
}

static ssize_t gec6818_led_write (struct file * file, const char __user * buf, size_t len, loff_t * off)
//读写接口定义
{
    
	int rt,v;
	unsigned char kbuf[64]={
    0};
	if(len > sizeof kbuf)
	return -EINVAL;		//返回参数无效错误码
	//常见错误码，这个错误码每个芯片都不一样要在内核里面找error文件
	#if 0
	#define EPERM 1 /*Operation not permitted */
	#define ENOENT 2 /* No such file or directory */
	#define ESRCH 3 /* No such process */
	#define EINTR 4 /* Interrupted system call */
	#define EIO 5 /* I/O error */
	#define ENXIO 6 /* No such device or address */
	#define E2BIG 7 /* Argument list too long */
	#define ENOEXEC 8 /* Exec format error */
	#define EBADF 9 /* Bad file number */
	#define ECHILD 10 /* No child processes */
	#define EAGAIN 11 /* Try again */
	#define ENOMEM 12 /* Out of memory */
	#define EACCES 13 /* Permission denied */
	#define EFAULT 14 /* Bad address */
	#define ENOTBLK 15 /* Block device required */
	#define EBUSY 16 /* Device or resource busy */
	#define EEXIST 17 /* File exists */
	#define EXDEV 18 /* Cross-device link */
	#define ENODEV 19 /* No such device */
	#define ENOTDIR 20 /* Not a directory */
	#define EISDIR 21 /* Is a directory */
	#define EINVAL 22 /* Invalid argument */
	#define ENFILE 23 /* File table overflow */
	#define EMFILE 24 /* Too many open files */
	#define ENOTTY 25 /* Not a typewriter */
	#define ETXTBSY 26 /* Text file busy */
	#define EFBIG 27 /* File too large */
	#define ENOSPC 28 /* No space left on device */
	#define ESPIPE 29 /* Illegal seek */
	#define EROFS 30 /* Read-only file system */
	#define EMLINK 31 /* Too many links */
	#define EPIPE 32 /* Broken pipe */
	#define EDOM 33 /* Math argument out of domain of func */
	#define ERANGE 34 /* Math result not representable */
	#endif
	rt = copy_from_user(kbuf,buf,len);
	//将用户空间的数据拷贝到内核空间
	//如果不改值，可不使用这个函数，直接获取buf里面内容
	//获取成功复制的字节数
	
	len = len - rt;

	switch(kbuf[0]){
    
		case 7:{
    
			if(kbuf[1]==1){
    
				v = ioread32(gpioe_out_va);
				v &=~(1<<13);
				iowrite32(v,gpioe_out_va);
			}else{
    
				v = ioread32(gpioe_out_va);
				v |=(1<<13);
				iowrite32(v,gpioe_out_va);			
			}
		}break;
	}
	printk("[gec6818_led_write]kbuf[0]=%d,kbuf[1]=%d\n",kbuf[0],kbuf[1]);	
	
	return len;
}

static ssize_t gec6818_led_read (struct file *file, char __user *buf, size_t len, loff_t * offs)
//读写接口定义
{
    
	
	int rt;
	
	char kbuf[6]={
    '1','2','3','4','\n','\0'};	
	
	//判断当前len是否合法
	if(len > sizeof kbuf)
		return -EINVAL;		//返回参数无效错误码
		
	//从内核空间拷贝到用户空间
	
	rt = copy_to_user(buf,kbuf,len);
	
	//获取成功复制的字节数
	
	len = len - rt;
	
	printk("gec6818_led_read,__user buf[%s],len[%d]\n",buf,len);
	
	return len;
}

static const struct file_operations gec6818_led_fops = {
    
 	.owner 		= THIS_MODULE,
	.write 		= gec6818_led_write,
	.open 		= gec6818_led_open,
	.release 	= gec6818_led_release,
	.read		= gec6818_led_read,
};
//定义file_operations，初始化打开、关闭、读、写等函数接口，这是应用和驱动的交通枢纽

//这个是驱动的入口函数类似main
static int __init gec6818_led_init(void){
    
	int rt;	
	struct resource *gpioe_res=NULL;
	rt=alloc_chrdev_region(&led_num,0,1,"gec6818_leds");
	//动态分配，就是由内核自动分配空闲的设备号
	if(rt < 0)
	{
    
		printk("alloc_chrdev_region fail\n");
		
		return rt;
		
	}
	printk("led_major = %d\n",MAJOR(led_num));
	printk("led_minor = %d\n",MINOR(led_num));
	//获取分配后的主设备号和次设备号

	//字符设备初始化
	cdev_init(&gec6818_led_cdev,&gec6818_led_fops);
	
	//字符设备添加到内核
	rt = cdev_add(&gec6818_led_cdev,led_num,1);

	if(rt < 0)
	{
    
		printk("cdev_add fail\n");
		goto fail_cdev_add;
		
	}
	

	leds_class=class_create(THIS_MODULE, "gec6818_leds");
	//为设备创建一个class 类
	if (IS_ERR(leds_class))
	//如何判断当前的指针为错误码，使用IS_ERR函数进行判断
	{
    
		rt = PTR_ERR(leds_class);
		//PTR_ERR返回指针错误码数值
		printk("class_create gec6818_leds fail\n");
		
		goto fail_class_create;
		
	}
	
	//创建设备
	leds_device=device_create(leds_class, NULL, led_num, NULL, "gec6818_leds");
	
	if (IS_ERR(leds_device))
	{
    
		rt = PTR_ERR(leds_device);
		
		printk("device_create gec6818_leds fail\n");
		
		goto fail_device_create;
		
	}


	//起始地址GPIOE寄存器基址0xC001E000(这个地址可以参考之前那篇文章<三星6818基于uboot的流水灯程序>)
	//申请大小28字节
	//申请到的名字为GPIOE_MEM
	gpioe_res = request_mem_region(0xC001E000,0x28,"GPIOE_MEM");
	//申请物理内存区
	if(gpioe_res == NULL)
	{
    
		
		printk("request_mem_region 0xC001E000,0x28 fail\n");
		
		goto fail_request_mem_region_gpioe;		
		
	}
	
	//IO内存动态映射，得到物理地址相应的虚拟地址
	gpioe_base_va = ioremap(0xC001E000,0x28);
	
	if(gpioe_base_va == NULL)
	{
    
		
		printk("ioremap 0xC001E000,0x28 fail\n");
		
		goto fail_ioremap_gpioe;		
		
	}	
	
	//得到每个寄存器的虚拟地址
	gpioe_out_va 		= gpioe_base_va+0x00;
	gpioe_outenb_va 	= gpioe_base_va+0x04;	
	
	gpioe_altfn0_va 	= gpioe_base_va+0x20;		
	gpioe_altfn1_va 	= gpioe_base_va+0x24;	
	

	
	printk("gec6818 led init\n");
	
	return 0;

	fail_ioremap_gpioe:
	release_mem_region(0xC001E000,0x28);	
	//释放物理内存区

	fail_request_mem_region_gpioe:
	iounmap(gpioe_base_va);
	//解除IO内存的动态映射

	fail_device_create:
	class_destroy(leds_class);
	//类的销毁

	fail_class_create:
	cdev_del(&gec6818_led_cdev);
	//将字符设备从内核删除

	fail_cdev_add:
	unregister_chrdev_region(led_num,1);
	//设备号的注销
	return rt;
}
//在驱动有入口函数对应就有出口函数，用于释放资源，销毁设备号等等
static void __exit gec6818_led_exit(void){
    

	iounmap(gpioe_base_va);

	release_mem_region(0xC001E000,0x28);

	device_destroy(leds_class,led_num);
	//设备的销毁	

	class_destroy(leds_class);
	
	cdev_del(&gec6818_led_cdev);
	
	unregister_chrdev_region(led_num,1);
	
	printk("gec6818 led exit\n");
}

//驱动程序的入口：insmod led_drv.ko调用module_init，module_init又会去调用gec6818_led_init。
module_init(gec6818_led_init);

//驱动程序的出口：rmsmod led_drv调用module_exit，module_exit又会去调用gec6818_led_exit。
module_exit(gec6818_led_exit);
//模块描述
MODULE_AUTHOR("[email protected]");			//作者信息
MODULE_DESCRIPTION("gec6818 led driver");		//模块功能说明
MODULE_LICENSE("GPL");					//许可证：驱动遵循GPL协议，这个必须加，否则会导致驱动异常

驱动的编译和生成

  1. 查看kernel/Documentation/kbuild的kbuild.txt编写Makefile
  2. 附上代码：
obj-m +=led_drv.o
/* Loadable module goals - obj-m $(obj-m) specify object files which are built as loadable kernel modules. A module may be built from one source file or several source files. In the case of one source file, the kbuild makefile simply adds the file to $(obj-m). Example: #drivers/isdn/i4l/Makefile obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm' If a kernel module is built from several source files, you specify that you want to build a module in the same way as above; however, kbuild needs to know which object files you want to build your module from, so you have to tell it by setting a $(<module_name>-y) variable. */
KERNEL_DIR :=/home/jiba/6818SoucereCode/6818GEC/kernel
CROSS_COMPILE :=/home/jiba/6818SoucereCode/6818GEC/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8/bin/arm-eabi-
PWD:=$(shell pwd)

default:
	$(MAKE) ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) -C $(KERNEL_DIR) M=$(PWD) modules

clean:
	rm  *.o *.order .*.cmd  *.mod.c *.symvers .tmp_versions -rf

编写程序代码

  1. 附上代码
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

static char d7_on [2]={
    7,1};
//驱动write函数switch判断如果d7_on[1]为1就灭0就亮
static char d7_off[2]={
    7,0};

int main(int argc, char **argv)
{
    
	int fd=-1;
	
	int len;
	
	char buf[64]="hello teacher.wen";
	
	//打开gec6818_leds设备
	fd = open("/dev/gec6818_leds",O_RDWR);
	
	if(fd < 0)
	{
    
		perror("open /dev/gec6818_leds:");
		
		return fd;
		
	}
	
	while(1){
    
		write(fd,d7_on,2);
		sleep(2);
		write(fd,d7_off,2);
		sleep(2);
	}
	
	close(fd);
	
	return 0;
}

下载驱动(.ko)和程序到板子

在这里插入图片描述
insmod 加载驱动
运行程序OK~~~
要源码可以找我拿，wx：a812417530
如果对你有帮忙麻烦点赞收藏一下~~~~

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版权声明
本文为[I＆You]所创，转载请带上原文链接，感谢
https://blog.csdn.net/a812417530/article/details/110544681

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