相关知识：Linux设备驱动开发
insmod 编译好的.ko文件后再运行beep_app.c编译完成的可执行文件即可使板子蜂鸣。
beep_drv.c:
#include <linux/module.h> //包含了加载模块时需要使用的大量符号和函数声明
#include <linux/kernel.h> //包含了printk内核打印函数等函数声明
#include <linux/init.h> //包含了模块加载函数和模块释放函数的宏定义
#include <linux/errno.h>
#include <linux/cdev.h>
#include<linux/fs.h>
#include <linux/device.h>
#include <linux/ioport.h>
#include <linux/io.h>
#include <linux/uaccess.h>
int devno_major=0;//beep的主设备号
int devno_minor=0;//beep的次设备号
struct class *beep_class;
struct device *beep_device;
struct resource *beep_resource;
void __iomem *gpioc_base_va;
void __iomem *gpiocout_va;
void __iomem *gpiocoutenb_va;
void __iomem *gpiocaltfn0_va;
void __iomem *gpiocaltfn1_va;
void __iomem *gpiocpad_va;
module_param(devno_major,int,0660);
module_param(devno_minor,int,0660);
enum beep_state{BEEP_OFF,BEEP_ON};
int beep_state=BEEP_OFF;
/*1、定义一个字符设备 ---> struct cdev*/
struct cdev beep_cdev;
/*2、定义并初始化字符设备的文件操作集 ---> struct file_operations*/
int gec6818_beep_open(struct inode *inode, struct file *filp)
{
printk("beep have been opened!\n");
return 0;
}
ssize_t gec6818_beep_read (struct file *filp, char __user *user_buf,size_t size, loff_t *off)
{
int r = copy_to_user(user_buf, (void*)&beep_state, size);
if(r != 0)
return EINVAL;
return size;
}
ssize_t gec6818_beep_write (struct file *filp, const char __user *user_buf, size_t size, loff_t *off)
{
int r = copy_from_user((void*)&beep_state, user_buf, size);
if(r != 0)
return EINVAL;
if(beep_state == BEEP_ON)
writel(readl(gpiocout_va)|(0x01<<14),gpiocout_va);
else
writel(readl(gpiocout_va)&(~(0x01<<14)),gpiocout_va);
return size;
}
int gec6818_beep_release (struct inode *inode, struct file *filp)
{
printk("beep have been closed!\n");
return 0;
}
static const struct file_operations gec6818_beep_fops = {
.owner = THIS_MODULE,
.open = gec6818_beep_open,
.read = gec6818_beep_read,
.write = gec6818_beep_write,
.release = gec6818_beep_release
};
//入口函数 -->安装驱动
static int __init gec6818_beep_init(void)
{
dev_t devno;//beep的设备号
int ret=0;
/*3、给字符设备申请一个设备号 ---> 设备号=主设备号<<20 + 次设备号*/
if(devno_major != 0)
{
devno = MKDEV(devno_major,devno_minor);
if(register_chrdev_region(devno, 1, "gec6818_beep"))
{
printk("register_chrdev_region error!\n");
if(alloc_chrdev_region(&devno, devno_minor, 1, "gec6818_beep"))
{
printk("alloc_chrdev_region error!\n");
ret = EINVAL;
goto alloc_chrdev_region_err;
}
}
}
else
{
if(alloc_chrdev_region(&devno, devno_minor, 1, "gec6818_beep"))
{
printk("alloc_chrdev_region error!\n");
ret = EINVAL;
goto alloc_chrdev_region_err;
}
}
devno_major = MAJOR(devno);
devno_minor = MINOR(devno);
/*4、初始化字符设备*/
cdev_init(&beep_cdev, &gec6818_beep_fops);
/*5、将字符设备加入内核*/
if(cdev_add(&beep_cdev, devno, 1)<0)
{
ret = EINVAL;
goto cdev_add_err;
}
/*6、创建class*/
beep_class = class_create(THIS_MODULE, "gec6818_beep");
if(beep_class == NULL)
{
ret = EBUSY;
goto class_create_err;
}
/*7、创建device*/
beep_device = device_create(beep_class, NULL,devno, NULL, "gec6818_beep");
if(beep_device == NULL)
{
ret = EBUSY;
goto device_create_err;
}
/*8、申请物理内存区*/
beep_resource = request_mem_region(0xC001C000, 0x1000, "GPIOC_MEM");
if(beep_resource == NULL)
{
ret = EBUSY;
goto request_mem_region_err;
}
/*9、IO内存动态映射，得到虚拟地址*/
gpioc_base_va = ioremap(0xC001C000, 0x1000);
if(gpioc_base_va == NULL)
{
ret = EBUSY;
goto ioremap_err;
}
/*10、使用虚拟地址，把beep进行初始化*/
gpiocout_va = gpioc_base_va + 0x00;
gpiocoutenb_va = gpioc_base_va + 0x04;
gpiocaltfn0_va = gpioc_base_va + 0x20;
gpiocaltfn1_va = gpioc_base_va + 0x24;
gpiocpad_va = gpioc_base_va + 0x18;
//GPIOCALTFN0 &= ~(0x03<<28);//把GPIOC14设置为GPIO功能
writel(readl(gpiocaltfn0_va)&(~(0x03<<28)),gpiocaltfn0_va);
//GPIOCALTFN0 |= (0x01<<28);
writel(readl(gpiocaltfn0_va)|((0x01<<28)),gpiocaltfn0_va);
//GPIOCOUTENB |= 1<<14;//把GPIOC14设置为输出模式
writel(readl(gpiocoutenb_va)|((0x01<<14)),gpiocoutenb_va);
//GPIOCOUT &= ~(1<<14);//把GPIOC14输出低电平，默认beep不响
writel(readl(gpiocout_va)&(~(0x01<<14)),gpiocout_va);
printk("gec6818 beep init success!\n");
return 0;
ioremap_err:
release_mem_region(0xC001C000, 0x1000);
request_mem_region_err:
device_destroy(beep_class, devno);
device_create_err:
class_destroy(beep_class);
class_create_err:
cdev_add_err:
unregister_chrdev_region(devno, 1);//注销设备号
alloc_chrdev_region_err:
return ret;
}
//出口函数 -->卸载驱动
static void __exit gec6818_beep_exit(void)
{
iounmap(gpioc_base_va);
release_mem_region(0xC001C000, 0x1000);
device_destroy(beep_class, MKDEV(devno_major,devno_minor));
class_destroy(beep_class);
unregister_chrdev_region(MKDEV(devno_major,devno_minor), 1);//注销设备号
printk("6818gec beep exit\n ");
}
//驱动程序的入口: #insmod hello.ko ==> module_init() ==> gec6868_hello_init();
module_init(gec6818_beep_init);
//驱动程序的出口: #rmmod hello.ko ==> module_exit() ==> gec6818_hello_exit();
module_exit(gec6818_beep_exit);
//module的描述： #modinfo hello.ko
MODULE_AUTHOR("GEC_Liudehua@163.com");
MODULE_DESCRIPTION("beep driver for GEC6818");
MODULE_LICENSE("GPL");
MODULE_VERSION("V1.0");
beep_app.c:
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
int beep_state;
int readbuf;
int main()
{
int fd = open("/dev/gec6818_beep",O_RDWR);
if(fd == -1)
{
printf("open failed!\n");
return -1;
}
while(1)
{
beep_state=1;
int r = write(fd,&beep_state,4);
if(r !=4 )
{
printf("write error!\n");
}
read(fd,&readbuf,4);
printf("read buf is %d\n",readbuf);
sleep(2);
beep_state=0;
write(fd,&beep_state,4);
read(fd,&readbuf,4);
printf("read buf is %d\n",readbuf);
sleep(2);
}
}
makefile:
#KERNELRELEASE这个变量，在内核源码的根目录下面的Makefile会初初始化的
ifeq ($(KERNELRELEASE),)
KERN_DIR := /home/china/6818GEC/kernel
#在Makefile中可以调用shell的命令，调用方法如下:
# $(shell shell命令) -> 整个这个表达式，表示调用该shell命令的输出结果
PWD := $(shell pwd)
CROSS_COMPILE := /home/china/6818GEC/prebuilts/gcc/linux-x86/arm/arm-eabi-4.8/bin/arm-eabi-
modules:
make -C $(KERN_DIR) M=$(PWD) ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) modules
clean:
rm -rf *.o
rm -rf modules.order .tmp_versions *.ko Module.symvers
rm -f *.cmd .*.cmd *.mod.c
else
obj-m += beep_drv.o
endif