20155223 20155207实验四 外设驱动程序设计
任务一
实验要求
1）学习资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章
2）提交康奈尔笔记的照片
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二
实验要求
1）在Ubuntu完成资源中全课中的“hqyj.嵌入式Linux应用程序开发标准教程.pdf”中的第十一章的test试验
2）提交编译，加载模块，卸载模块，测试运行的截图（要多张，全屏，体现学号信息）
实验目的
该实验是编写最简单的字符驱动程序，这里的设备也就是一段内存，实现简单的读写功能，并列出常用格式的Makefile以及驱动的加载和卸载脚本。读者可以熟悉字符设备驱动的整个编写流程
实验内容
该实验要求实现对虚拟设备（一段内存）的打开、关闭、读写的操作，并要通过编写测试程序来测试虚拟设备及其驱动运行是否正常。
test_drv.c代码
#include#include #include #include #include #include #include #include #include #define TEST_DEVICE_NAME "test_dev"#define BUFF_SZ 1024static struct cdev test_dev;unsigned int major =0;static char *data = NULL;/*º¯ÊýÉùÃ÷*/static ssize_t test_read(struct file *file, char *buf, size_t count, loff_t *f_pos);static ssize_t test_write(struct file *file,const char *buffer, size_t count,loff_t *f_pos);static int test_open(struct inode *inode, struct file *file);static int test_release(struct inode *inode,struct file *file);static ssize_t test_read(struct file *file, char *buf, size_t count, loff_t *f_pos){ int len; if (count < 0 ) { return -EINVAL; } len = strlen(data); count = (len > count)?count:len; if (copy_to_user(buf, data, count)) { return -EFAULT; } return count;}static ssize_t test_write(struct file *file, const char *buffer, size_t count, loff_t *f_pos){ if(count < 0) { return -EINVAL; } memset(data, 0, BUFF_SZ); count = (BUFF_SZ > count)?count:BUFF_SZ; if (copy_from_user(data, buffer, count)) { return -EFAULT; } return count;}static int test_open(struct inode *inode, struct file *file){ printk("This is open operation\n"); data = (char*)kmalloc(sizeof(char) * BUFF_SZ, GFP_KERNEL); if (!data) { return -ENOMEM; } memset(data, 0, BUFF_SZ); return 0;}static int test_release(struct inode *inode,struct file *file){ printk("This is release operation\n"); if (data) { kfree(data); data = NULL; } return 0;}static void test_setup_cdev(struct cdev *dev, int minor, struct file_operations *fops){ int err, devno = MKDEV(major, minor); cdev_init(dev, fops); dev->owner = THIS_MODULE; dev->ops = fops; err = cdev_add (dev, devno, 1); if (err) { printk (KERN_NOTICE "Error %d adding test %d", err, minor); }}static struct file_operations test_fops = { .owner = THIS_MODULE, .read = test_read, .write = test_write, .open = test_open, .release = test_release,};int init_module(void){ int result; dev_t dev = MKDEV(major, 0); if (major) { result = register_chrdev_region(dev, 1, TEST_DEVICE_NAME); } else { result = alloc_chrdev_region(&dev, 0, 1, TEST_DEVICE_NAME); major = MAJOR(dev); } if (result < 0) { printk(KERN_WARNING "Test device: unable to get major %d\n", major); return result; } test_setup_cdev(&test_dev, 0, &test_fops); printk("The major of the test device is %d\n", major); return 0;}void cleanup_module(void) { cdev_del(&test_dev); unregister_chrdev_region(MKDEV(major, 0), 1); printk("Test device uninstalled\n");}test.c代码如下：/* test.c */#include #include #include #include #include #include #include #define TEST_DEVICE_FILENAME "/dev/test_dev"#define BUFF_SZ 1024int main(){ int fd, nwrite, nread; char buff[BUFF_SZ]; fd = open(TEST_DEVICE_FILENAME, O_RDWR); if (fd < 0) { perror("open"); exit(1); } do { printf("Input some words to kernel(enter 'quit' to exit):"); memset(buff, 0, BUFF_SZ); if (fgets(buff, BUFF_SZ, stdin) == NULL) { perror("fgets"); break; } buff[strlen(buff) - 1] = '\0'; if (write(fd, buff, strlen(buff)) < 0) { perror("write"); break; } if (read(fd, buff, BUFF_SZ) < 0) { perror("read"); break; } else { printf("The read string is from kernel:%s\n", buff); } } while(strncmp(buff, "quit", 4)); close(fd); exit(0);}
Makefile
ifeq ($(KERNELRELEASE),)KERNELDIR ?= /lib/modules/$(shell uname -r)/buildPWD := $(shell pwd)modules: $(MAKE) -C $(KERNELDIR) M=$(PWD) modulesmodules_install: $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_installclean: rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions.PHONY: modules modules_install cleanelse obj-m := test_drv.oendiftest_drv_load脚本内容如下：#!/bin/shmodule="test_drv"device="test_dev"mode="664"group="david"# remove stale nodesrm -f /dev/${device} # invoke insmod with all arguments we got# and use a pathname, as newer modutils don't look in . by default/sbin/insmod -f ./$module.ko $* || exit 1major=`cat /proc/devices | awk "\\$2==\"$device\" {print \\$1}"`mknod /dev/${device} c $major 0# give appropriate group/permissionschgrp $group /dev/${device}chmod $mode /dev/${device} 加载模块
/*test_drv_load*/#!/bin/sh# 驱动模块名称module="test_drv" # 设备名称。在/proc/devices中出现device="test_dev" # 设备文件的属性mode="664" group="david" # 删除已存在的设备节点rm -f /dev/${device} # 加载驱动模块/sbin/insmod -f ./$module.ko $* || exit 1# 查到创建设备的主设备号major=`cat /proc/devices | awk "\\$2==\"$device\" {print \\$1}"`# 创建设备文件节点mknod /dev/${device} c $major 0# 设置设备文件属性chgrp $group /dev/${device}chmod $mode /dev/${device} 测试代码
/* test.c */#include#include #include #include #include #include #include #define TEST_DEVICE_FILENAME "/dev/test_dev" /* 设备文件名*/#define BUFF_SZ 1024 /* 缓冲大小 */ int main(){ int fd, nwrite, nread; char buff[BUFF_SZ]; /*缓冲区*/ /* 打开设备文件 */ fd = open(TEST_DEVICE_FILENAME, O_RDWR); if (fd < 0) { perror("open"); exit(1); } do { printf("Input some words to kernel(enter 'quit' to exit):"); memset(buff, 0, BUFF_SZ); if (fgets(buff, BUFF_SZ, stdin) == NULL) { perror("fgets"); break; } buff[strlen(buff) - 1] = '\0'; if (write(fd, buff, strlen(buff)) < 0) /* 向设备写入数据 */ { perror("write"); break; } if (read(fd, buff, BUFF_SZ) < 0) /* 从设备读取数据 */ { perror("read"); break; } else { printf("The read string is from kernel:%s\n", buff); } } while(strncmp(buff, "quit", 4)); close(fd); exit(0);}
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