常用driver模板

给应用程序写read,write驱动

头文件

#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);

定义传统的设备文件访问方法，主要是定义hello_open、hello_release、hello_read和hello_write这四个打开、释放、读和写设备文件的方法：

/*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;}

定义通过devfs文件系统访问方法，这里把设备的寄存器val看成是设备的一个属性，通过读写这个属性来对设备进行访问，主要是实现hello_val_show和hello_val_store两个方法，同时定义了两个内部使用的访问val值的方法__hello_get_val和__hello_set_val：

/*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);}

定义通过proc文件系统访问方法，主要实现了hello_proc_read和hello_proc_write两个方法，同时定义了在proc文件系统创建和删除文件的方法hello_create_proc和hello_remove_proc：

/*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);}

最后，定义模块加载和卸载方法，这里只要是执行设备注册和初始化操作：

/*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);