Android驱动开发-第一个安卓驱动程序

参考博客:https://blog.csdn.net/u011913612/article/details/52516303?utm_medium=distribute.pc_relevant.none-task-blog-OPENSEARCH-3.channel_param&depth_1-utm_source=distribute.pc_relevant.none-task-blog-OPENSEARCH-3.channel_param

1.驱动程序

frist_driver.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/cdev.h>
#include <linux/device.h>
#include <linux/of.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define HELLOON               1
#define HELLOOFF              0        
#define HELLO_CNT             1
#define HELLO_NAME           "hello driver"

static char readbuf[100];
static char writebuf[100];
static char kerneldata[] = {"hello my first driver"};
static char mybuf[100]   ="1234";

struct hello_driver
{
    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*/
    atomic_t        atomic_lock;      /*原子变量*/ 
};

struct hello_driver hello_driver_dev;

static ssize_t show_my_device(struct device *dev,struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", mybuf);
}

static ssize_t set_my_device(struct device *dev,struct device_attribute *attr, const char *buf, size_t len)//echo命令时,将会调用该函数
{
    sprintf(mybuf, "%s", buf);
    return len;
}

static DEVICE_ATTR(my_device_test, S_IWUSR|S_IRUSR, show_my_device, set_my_device);
                //定义一个名字为my_device_test的设备属性文件

static int hello_driver_open(struct inode *inode, struct file *filp)
{
   if(!atomic_dec_and_test(&hello_driver_dev.atomic_lock))
   {
       atomic_inc(&hello_driver_dev.atomic_lock);
       return -EBUSY;           
   }

    filp->private_data = &hello_driver_dev;
    return 0;
}

static ssize_t hello_driver_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)
{
    int ret = 0;

    memcpy(readbuf,kerneldata,sizeof(kerneldata));
    ret = copy_to_user(buf,readbuf,cnt);
    if(ret == 0)
    {
        printk("kernel senddata ok!\n");
    }else
    {
        printk("kernel senddata failed\n");
    }

    return 0;
}

static ssize_t hello_driver_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
    int ret = 0;

    ret = copy_from_user(writebuf,buf,cnt);
    if(ret == 0)
    {
        printk("kernel recvdata %s\n",writebuf);
    }else
    {
        printk("kernel recvdata failed\n");
    }

    return 0;
}

static long hello_driver_unlocked_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
    
    switch(cmd)
    {
        case HELLOON:  
            printk("Open hello driver\n");
            break;
        case HELLOOFF:   
            printk("Close hello driver\n");
            break;
        default:
            break;
    }
    return 0;
}

static int hello_driver_release(struct inode *inode, struct file *filp)
{
    struct hello_driver *dev = filp->private_data;
    atomic_inc(&dev->atomic_lock);
    return 0;
}

static struct file_operations hello_driver_fops= {
    .owner             = THIS_MODULE,
    .open              = hello_driver_open, 
    .read              = hello_driver_read,
    .write             = hello_driver_write,
    .unlocked_ioctl    = hello_driver_unlocked_ioctl,
    .release           = hello_driver_release,
};

static int __init hello_driver_init(void)
{
    int ret;
    /*1.设置原子变量，保证同一时刻只能有一个应用程序使用该驱动*/
    atomic_set(&hello_driver_dev.atomic_lock,1);

    /*2.分配设备号*/
    /*2.1 之前分配了主设备号*/
    if(hello_driver_dev.major)
    {
        /*注册设备号*/
        hello_driver_dev.devid = MKDEV(hello_driver_dev.major,0);
        ret = register_chrdev_region(hello_driver_dev.devid, HELLO_CNT, HELLO_NAME);
        if(ret < 0)
        {
            printk("can't register major\n");  
            return ret; 
        }
    }else/*2.2 之前未分配设备号，向内核申请设备号*/
    {
       alloc_chrdev_region(&hello_driver_dev.devid, 0, HELLO_CNT, HELLO_NAME); 
    }

    printk(KERN_ERR"hello_driver_dev major = %d, minor = %d\n", hello_driver_dev.major,
            hello_driver_dev.minor);

    hello_driver_dev.cdev.owner = THIS_MODULE;
    cdev_init(&hello_driver_dev.cdev,&hello_driver_fops);
    ret = cdev_add(&hello_driver_dev.cdev, hello_driver_dev.devid,HELLO_CNT);
    if(ret)
    {
        printk("Error cdev_add\n");  
        goto fail_to_cdev_add;
    }

    hello_driver_dev.class = class_create(THIS_MODULE,HELLO_NAME);
    if(IS_ERR(hello_driver_dev.class))
    {
        goto fail_to_class_create;
    }

    hello_driver_dev.device = device_create(hello_driver_dev.class , NULL, hello_driver_dev.devid, NULL, HELLO_NAME);
    if(IS_ERR(hello_driver_dev.device))
    {
        goto fail_to_device_create;
    }

 if(sysfs_create_file(&hello_driver_dev.device ->kobj), &dev_attr_my_device_test.attr))
{    
     //在mytest_device设备目录下创建一个my_device_test属性文件
       return -1;
}
	
return 0;

fail_to_cdev_add:
    unregister_chrdev_region(hello_driver_dev.devid, HELLO_CNT); 
	return -1;
fail_to_class_create:
    cdev_del(&hello_driver_dev.cdev);
    unregister_chrdev_region(hello_driver_dev.devid, HELLO_CNT);
    return -1;	
fail_to_device_create:
    cdev_del(&hello_driver_dev.cdev);
    unregister_chrdev_region(hello_driver_dev.devid, HELLO_CNT); 
    class_destroy(hello_driver_dev.class);
	return -1;
}

static void __exit hello_driver_exit(void)
{
    cdev_del(&hello_driver_dev.cdev);
    unregister_chrdev_region(hello_driver_dev.devid, HELLO_CNT); 

    device_destroy(hello_driver_dev.class, hello_driver_dev.devid); 
    class_destroy(hello_driver_dev.class);
}

module_init(hello_driver_init);
module_exit(hello_driver_exit);
MODULE_DESCRIPTION("my hello driver");
MODULE_AUTHOR("Kong Lingze");
MODULE_LICENSE("GPL");

2.加载驱动程序编译到内核

添加文件夹

在kernel/driver目录下添加新的文件夹frist_driver,在frist_driver中添加文件Kconfig,Makefile,frist_driver.c

frist_driver/Kconfig中的内容:

frist_driver/Makefile中的内容:

在driver/Kconfig添加内容:

在driver/Makefile添加内容:

• 在kernel/driver下执行make menuconfig,选择First Android Driver
• 在安卓源码目录目录下source build/envsetup.sh
• lunch xx xxxx (可选择)
• make bootimage -j32

测试:

执行fastboot flash boot boot.img将内核烧写到开发板,在开发板目录找到sys/class/hello driver/hello driver或者下图目录,执行如图的命令

测试成功

3.用c程序进行测试

首先在android源码的packages目录下新建一个helloapp目录，该目录下新建hello_app.c和Android.mk两个文件。

hello_app.c

#include <stdio.h>
#include <unistd.h> 
#include <sys/types.h> 
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h> 
#include <string.h>
#include <sys/ioctl.h>


#define READ           3
#define WRITE          4
#define HELLO_ON       1
#define HELLO_OFF      0

// ./app /dev/hello\driver  <cmd>
static unsigned char cUserData[] = {"User data"};
int main(int argc, char **argv)
{
    int  iFd;
    int  iRet;
    char *cFilename;

    unsigned int  arg = 0;
    unsigned char cReadBuf[100];
    unsigned char cWriteBuf[100];

    if(argc!=3)
	{
		Printf(“Usage:%s <file inode> <cmd>”,argv[0]);
	}
    //打开设备结点
    cFilename = argv[1];
    iFd = open(cFilename, O_RDWR);
    if(iFd < 0)
    {
        printf(" open %s failed\n", cFilename);
        return -1;
    }

    /*读取驱动中的数据*/
    if(atoi(argv[2]) == READ)
    {
        memset(cReadBuf,sizeof(cReadBuf),sizeof(cReadBuf));
        iRet = read(iFd,cReadBuf,sizeof(cReadBuf));
        if(iRet < 0)
        {
            printf("read %s data failed\n",cFilename);
            return -1;
        }else
        {
            printf("read data is:%s\n",cReadBuf);
        }
    }else if(atoi(argv[2]) == WRITE)//向驱动中写数据
    {
        memset(cWriteBuf,sizeof(cWriteBuf),sizeof(cWriteBuf));
        memcpy(cWriteBuf,cUserData,sizeof(cUserData));

        iRet = write(iFd,cWriteBuf,sizeof(cWriteBuf));
        if(iRet < 0)
        {
            printf("write %s data failed\n",cFilename);
            return -1;
        }
    }else if(atoi(argv[2]) == HELLO_ON)//给驱动发送HELLO_ON命令
    {
        ioctl(iFd,HELLO_ON,arg);
    }else if(atoi(argv[2]) == HELLO_OFF)//给驱动发送HELLO_OFF命令
    {
        ioctl(iFd,HELLO_OFF,arg);
    }
    
    iRet = close(iFd);
    if(iFd < 0)
    {
        printf("close %s failed",cFilename);
        return -1;
    }

    return 0;
}

Andoird.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_MODULE := hellotest
LOCAL_SRC_FILES := $(call all-subdir-c-files)
include $(BUILD_EXECUTABLE)

编译

完成之后在安卓源码目录,输入source build\envser.up.sh,再进入packages/helloapp目录执行mm命令,生成可执行文件,编译后的文件在out/target/product/xxx/obj/EXECUTABLES/hellotapp_intermediates/中

测试

adb shell
adb push hello_app /data把hello_app推送到android设备的data目录下，
chmod +x helloapp添加可执行权限。
执行./helloapp /dev/hello driver 1

打印如下：
Open hello driver
可见测试成功。

本文地址：https://blog.csdn.net/weixin_43824344/article/details/107915758