接上篇内核编译继续编一个简单的随内核加载的驱动。
1、进入内核代码所在路径
2、cd goldfish/drivers
3、mkdir hello
4、cd hello
5、创建hello.h
- #ifndef _HELLO_ANDROID_H_
- #define _HELLO_ANDROID_H_
- #include <linux/cdev.h>
- #include <linux/semaphore.h>
- #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
6、创建hello.c
- #include <linux/init.h>
- #include <linux/module.h>
- #include <linux/types.h>
- #include <linux/fs.h>
- #include <linux/proc_fs.h>
- #include <linux/device.h>
- #include <asm/uaccess.h>
- #include "hello.h"
- /*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*/
- 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*/
- 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:
- 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*/
- if(down_interruptible(&(dev->sem))) {
- return -ERESTARTSYS;
- }
- val = dev->val;
- up(&(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*/
- if(down_interruptible(&(dev->sem))) {
- return -ERESTARTSYS;
- }
- dev->val = val;
- 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);
- }
- /*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;
- }
- /*创建/proc/hello文件*/
- static void hello_create_proc(void) {
- struct proc_dir_entry* entry;
-
- entry = create_proc_entry(HELLO_DEVICE_PROC_NAME, 0, NULL);
- if(entry) {
- entry->owner = THIS_MODULE;
- entry->read_proc = hello_proc_read;
- entry->write_proc = hello_proc_write;
- }
- }
- /*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);
- 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));
- 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);
- /*创建/proc/hello文件*/
- hello_create_proc();
- 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);
7、创建
Kconfig- config HELLO
- tristate "First Android Driver"
- default n
- help
- This is the first android driver.
8、创建Makefile
- obj-$(CONFIG_HELLO) += hello.o
9、进入内核源代码的goldfish/arch/arm路径
10、在Kconfig文件中的menu "Device Drivers"和endmenu之间添加:
source "drivers/hello/Kconfig"
11、进入内核源代码的goldfish/drivers路径
12、在Kconfig文件中的menu "Device Drivers"和endmenu之间添加:
source "drivers/hello/Kconfig"
13、在Makefile文件中添加:
obj-$(CONFIG_HELLO) += hello/
14、进入goldfish路径
15、make menuconfig
"Device Drivers" => "First Android Drivers"选项选中
16、make
17、emulator -kernel 内核源代码路径/goldfish/arch/arm/boot/zImage -avd a_avd&
18、adb shell
19、察看驱动是否随内核加载
ls /dev
ls /proc
20、验证驱动是否可用
- cd proc
- cat hello
- echo '5' > hello
- cat hello
- cd /sys/class
- cd hello
- cd hello
- cat val
- echo '0' > val
- cat val
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