Android11（RK3568）自定义服务制作(1)-Kernel驱动
最近在移植自己公司的产品进入新的Android系统中，需要用到自定义服务来调用自己的驱动。其实从Android4.0以来就没有再做过驱动开发，现在发现整个android11后，无论是驱动层还是JNI调用，HAL层到上层APP都有了很大的改动，最近也差了很多资料，发现各有各的问题。现在就我整理了一份从驱动到JNI到自定义service，其实还涉及到selinux的改写跟最后APP的调用，做个完整记录，为需要android11自定义服务的用户提供一份方便。本专栏分4个部分来写，从低到高。让你使用RK3568平台来实现自定义Service。
1.驱动篇
Android系统的内核从8.0开始就进入5时代。大量的平台都采用了最新的kernel5.0以上的版本。kernel5.0开始跟4.0的差距比较大，很多原来的写法已经不再适用了。
首先在kernel中的/arch/arm64/configs/firefly_defconfig中添加
# hello mod by sommerjiang
CONFIG_HELLO=y再在/drivers/misc/下面的Kconfig添加一下的内容：
source "drivers/misc/hello/Kconfig"Makefile中添加
obj-$(CONFIG_HELLO) += hello/
再在/drivers/misc/添加hello文件夹，并添加hello.c hello.h Kconfig Makefile四个文件，内容分别为
hello.c
#include
#include
#include
#include
#include
#include
#include
#include
#include "hello.h"
//#define use_proc_hello
/*主设备和从设备号变量*/
static int hello_major = 0;
static int hello_minor = 0;
/*设备类别和设备变量*/
static struct class* hello_class = NULL;
static struct hello_android_dev* hello_dev = NULL;
/*传统的设备文件操作方法*/
static int hello_open(struct inode* inode, struct file* filp);
static int hello_release(struct inode* inode, struct file* filp);
static ssize_t hello_read(struct file* filp, char __user *buf, size_t count, loff_t* f_pos);
static ssize_t hello_write(struct file* filp, const char __user *buf, size_t count, loff_t* f_pos);
/*设备文件操作方法表*/
static struct file_operations hello_fops = {
.owner = THIS_MODULE,
.open = hello_open,
.release = hello_release,
.read = hello_read,
.write = hello_write,
};
;
/*访问设置属性方法*/
static ssize_t hello_val_show(struct device* dev, struct device_attribute* attr, char* buf);
static ssize_t hello_val_store(struct device* dev, struct device_attribute* attr, const char* buf, size_t count);
/*定义设备属性*/ //sys/class/hello
static DEVICE_ATTR(val, S_IRUGO | S_IWUSR, hello_val_show, hello_val_store);
/*打开设备方法*/
static int hello_open(struct inode* inode, struct file* filp) {
struct hello_android_dev* dev;
/*将自定义设备结构体保存在文件指针的私有数据域中，以便访问设备时拿来用*/
dev = container_of(inode->i_cdev, struct hello_android_dev, dev);
filp->private_data = dev;
return 0;
}
/*设备文件释放时调用，空实现*/
static int hello_release(struct inode* inode, struct file* filp) {
return 0;
}
/*读取设备的寄存器val的值*/
static ssize_t hello_read(struct file* filp, char __user *buf, size_t count, loff_t* f_pos) {
ssize_t err = 0;
struct hello_android_dev* dev = filp->private_data;
/*同步访问*/
/*if(down_interruptible(&(dev->sem))) {
return -ERESTARTSYS;
} */
if(count < sizeof(dev->val)) {
goto out;
}
/*将寄存器val的值拷贝到用户提供的缓冲区*/
if(copy_to_user(buf, &(dev->val), sizeof(dev->val))) {
err = -EFAULT;
goto out;
}
err = sizeof(dev->val);
out:
//up(&(dev->sem));
return err;
}
/*写设备的寄存器值val*/
static ssize_t hello_write(struct file* filp, const char __user *buf, size_t count, loff_t* f_pos) {
struct hello_android_dev* dev = filp->private_data;
ssize_t err = 0;
/*同步访问*/
/* ly if(down_interruptible(&(dev->sem))) {
return -ERESTARTSYS;
} */
if(count != sizeof(dev->val)) {
goto out;
}
/*将用户提供的缓冲区的值写到设备寄存器去*/
if(copy_from_user(&(dev->val), buf, count)) {
err = -EFAULT;
goto out;
}
err = sizeof(dev->val);
out:
//ly up(&(dev->sem));
return err;
}
/*读取寄存器val的值到缓冲区buf中，内部使用*/
static ssize_t __hello_get_val(struct hello_android_dev* dev, char* buf) {
int val = 0;
/*同步访问*/
/*ly if(down_interruptible(&(dev->sem))) {
return -ERESTARTSYS;
} */
val = dev->val;
//lyup(&(dev->sem));
return snprintf(buf, PAGE_SIZE, "%d\n", val);
}
/*把缓冲区buf的值写到设备寄存器val中去，内部使用*/
static ssize_t __hello_set_val(struct hello_android_dev* dev, const char* buf, size_t count) {
int val = 0;
/*将字符串转换成数字*/
val = simple_strtol(buf, NULL, 10);
/*同步访问*/
/* ly if(down_interruptible(&(dev->sem))) {
return -ERESTARTSYS;
} */
dev->val = val;
// ly up(&(dev->sem));
return count;
}
/*读取设备属性val*/
static ssize_t hello_val_show(struct device* dev, struct device_attribute* attr, char* buf) {
struct hello_android_dev* hdev = (struct hello_android_dev*)dev_get_drvdata(dev);
return __hello_get_val(hdev, buf);
}
/*写设备属性val*/
static ssize_t hello_val_store(struct device* dev, struct device_attribute* attr, const char* buf, size_t count) {
struct hello_android_dev* hdev = (struct hello_android_dev*)dev_get_drvdata(dev);
return __hello_set_val(hdev, buf, count);
}
//old method for proc
#if 0
/*读取设备寄存器val的值，保存在page缓冲区中*/
static ssize_t hello_proc_read(char* page, char** start, off_t off, int count, int* eof, void* data) {
if(off > 0) {
*eof = 1;
return 0;
}
return __hello_get_val(hello_dev, page);
}
/*把缓冲区的值buff保存到设备寄存器val中去*/
static ssize_t hello_proc_write(struct file* filp, const char __user *buff, unsigned long len, void* data) {
int err = 0;
char* page = NULL;
if(len > PAGE_SIZE) {
printk(KERN_ALERT"The buff is too large: %lu.\n", len);
return -EFAULT;
}
page = (char*)__get_free_page(GFP_KERNEL);
if(!page) {
printk(KERN_ALERT"Failed to alloc page.\n");
return -ENOMEM;
}
/*先把用户提供的缓冲区值拷贝到内核缓冲区中去*/
if(copy_from_user(page, buff, len)) {
printk(KERN_ALERT"Failed to copy buff from user.\n");
err = -EFAULT;
goto out;
}
err = __hello_set_val(hello_dev, page, len);
out:
free_page((unsigned long)page);
return err;
}
#endif
/*创建/proc/hello文件*/
#ifdef use_proc_hello
static void hello_create_proc(void) {
//struct proc_dir_entry* entry;
//entry = create_proc_entry(HELLO_DEVICE_PROC_NAME, 0, NULL);
//proc_create(HELLO_DEVICE_PROC_NAME, 0, NULL, &hello_fops);
if(!proc_create(HELLO_DEVICE_PROC_NAME, 0666, NULL, &hello_fops)) {
printk("error ");
}
}
#endif
/*删除/proc/hello文件*/
static void hello_remove_proc(void) {
remove_proc_entry(HELLO_DEVICE_PROC_NAME, NULL);
}
/*初始化设备*/
static int __hello_setup_dev(struct hello_android_dev* dev) {
int err;
dev_t devno = MKDEV(hello_major, hello_minor); //jiang zhu
memset(dev, 0, sizeof(struct hello_android_dev));
cdev_init(&(dev->dev), &hello_fops);
dev->dev.owner = THIS_MODULE;
dev->dev.ops = &hello_fops;
/*注册字符设备*/
err = cdev_add(&(dev->dev),devno, 1);
if(err) {
return err;
}
/*初始化信号量和寄存器val的值*/
//init_MUTEX(&(dev->sem));
// ly sema_init(&(dev->sem),1);
dev->val = 0;
return 0;
}
/*模块加载方法*/
static int __init hello_init(void){
int err = -1;
dev_t dev = 0;
struct device* temp = NULL;
printk(KERN_ALERT"Initializing hello device.\n");
/*动态分配主设备和从设备号*/
err = alloc_chrdev_region(&dev, 0, 1, HELLO_DEVICE_NODE_NAME);
if(err < 0) {
printk(KERN_ALERT"Failed to alloc char dev region.\n");
goto fail;
}
hello_major = MAJOR(dev);
hello_minor = MINOR(dev);
/*分配helo设备结构体变量*/
hello_dev = kmalloc(sizeof(struct hello_android_dev), GFP_KERNEL);
if(!hello_dev) {
err = -ENOMEM;
printk(KERN_ALERT"Failed to alloc hello_dev.\n");
goto unregister;
}
/*初始化设备*/
err = __hello_setup_dev(hello_dev);
if(err) {
printk(KERN_ALERT"Failed to setup dev: %d.\n", err);
goto cleanup;
}
/*在/sys/class/目录下创建设备类别目录hello*/
hello_class = class_create(THIS_MODULE, HELLO_DEVICE_CLASS_NAME);
if(IS_ERR(hello_class)) {
err = PTR_ERR(hello_class);
printk(KERN_ALERT"Failed to create hello class.\n");
goto destroy_cdev;
}
/*在/dev/目录和/sys/class/hello目录下分别创建设备文件hello*/
temp = device_create(hello_class, NULL, dev, "%s", HELLO_DEVICE_FILE_NAME);
if(IS_ERR(temp)) {
err = PTR_ERR(temp);
printk(KERN_ALERT"Failed to create hello device.");
goto destroy_class;
}
/*在/sys/class/hello/hello目录下创建属性文件val*/
err = device_create_file(temp, &dev_attr_val);
if(err < 0) {
printk(KERN_ALERT"Failed to create attribute val.");
goto destroy_device;
}
dev_set_drvdata(temp, hello_dev);
#ifdef use_proc_hello
/*创建/proc/hello文件*/
hello_create_proc();
#endif
printk(KERN_ALERT"Succedded to initialize hello device.\n");
return 0;
destroy_device:
device_destroy(hello_class, dev);
destroy_class:
class_destroy(hello_class);
destroy_cdev:
cdev_del(&(hello_dev->dev));
cleanup:
kfree(hello_dev);
unregister:
unregister_chrdev_region(MKDEV(hello_major, hello_minor), 1);
fail:
return err;
}
/*模块卸载方法*/
static void __exit hello_exit(void) {
dev_t devno = MKDEV(hello_major, hello_minor);
printk(KERN_ALERT"Destroy hello device.\n");
/*删除/proc/hello文件*/
hello_remove_proc();
/*销毁设备类别和设备*/
if(hello_class) {
device_destroy(hello_class, MKDEV(hello_major, hello_minor));
class_destroy(hello_class);
}
/*删除字符设备和释放设备内存*/
if(hello_dev) {
cdev_del(&(hello_dev->dev));
kfree(hello_dev);
}
/*释放设备号*/
unregister_chrdev_region(devno, 1);
}
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("First Android Driver");
module_init(hello_init);
module_exit(hello_exit);
hello.h
#ifndef _HELLO_ANDROID_H_
#define _HELLO_ANDROID_H_
#include
#include
#define HELLO_DEVICE_NODE_NAME "hello"
#define HELLO_DEVICE_FILE_NAME "hello"
#define HELLO_DEVICE_PROC_NAME "hello"
#define HELLO_DEVICE_CLASS_NAME "hello"
struct hello_android_dev {
int val;
struct semaphore sem;
struct cdev dev;
};
#endif
Kconfig
config HELLO
tristate "First Android Driver"
default n
help
This is the first android driver.
Makefile
obj-$(CONFIG_HELLO) += hello.o这样编译完后就可以烧录到内核里面。完成驱动的编写。