1.安卓访问驱动-实现简单驱动

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。