Linux 设备驱动开发基础

Linux设备驱动开发基础1.Linux设备驱动概述什么是设备驱动-连接硬件设备和操作系统的桥梁-提供统一的接口给应用程序-处理硬件相关的细节操作驱动分类```c/*字符设备驱动*/structcdev{structkobjectkobj;structmodule*owner;conststructfile_operations*ops;//...};/*块设备驱动*/structblock_device{//...};/*网络设备驱动*/structnet_device{//...};```2.开发环境搭建所需工具```bash#安装开发工具sudoapt-getinstallbuild-essentiallinux-headers-$(uname-r)#查看内核版本uname-r#内核源码位置（通常）/lib/modules/$(uname-r)/build```编译系统```makefile#Makefile示例obj-m+=hello.oKDIR:=/lib/modules/$(shelluname-r)/buildPWD:=$(shellpwd)default: $(MAKE)-C$(KDIR)M=$(PWD)modulesclean: $(MAKE)-C$(KDIR)M=$(PWD)clean```3.最简单的字符设备驱动基本结构```c#include<linux/module.h>#include<linux/fs.h>#include<linux/cdev.h>#include<linux/device.h>#defineDEVICE_NAME"hello_dev"#defineCLASS_NAME"hello_class"staticintmajor_number;staticstructclass*hello_class=NULL;staticstructdevice*hello_device=NULL;staticstructcdevhello_cdev;//设备操作函数staticinthello_open(structinode*inodep,structfile*filep){printk(KERN_INFO"Hellodeviceopened\n");return0;}staticinthello_release(structinode*inodep,structfile*filep){printk(KERN_INFO"Hellodeviceclosed\n");return0;}staticssize_thello_read(structfile*filep,char*buffer,size_tlen,loff_t*offset){constchar*message="Hellofromkernel!\n";size_tmessage_len=strlen(message);if(*offset>=message_len)return0;if(len>message_len-*offset)len=message_len-*offset;if(copy_to_user(buffer,message+*offset,len))return-EFAULT;*offset+=len;returnlen;}//文件操作结构体staticstructfile_operationsfops={.open=hello_open,.read=hello_read,.release=hello_release,};//模块初始化staticint__inithello_init(void){printk(KERN_INFO"Hello:Initializingdriver\n");//分配设备号major_number=register_chrdev(0,DEVICE_NAME,&fops);if(major_number<0){printk(KERN_ALERT"Hello:failedtoregisterdevice\n");returnmajor_number;}//创建设备类hello_class=class_create(THIS_MODULE,CLASS_NAME);if(IS_ERR(hello_class)){unregister_chrdev(major_number,DEVICE_NAME);printk(KERN_ALERT"Hello:failedtocreateclass\n");returnPTR_ERR(hello_class);}//创建设备节点hello_device=device_create(hello_class,NULL,MKDEV(major_number,0),NULL,DEVICE_NAME);if(IS_ERR(hello_device)){class_destroy(hello_class);unregister_chrdev(major_number,DEVICE_NAME);printk(KERN_ALERT"Hello:failedtocreatedevice\n");returnPTR_ERR(hello_device);}printk(KERN_INFO"Hello:deviceregisteredwithmajor%d\n",major_number);return0;}//模块退出staticvoid__exithello_exit(void){device_destroy(hello_class,MKDEV(major_number,0));class_unregister(hello_class);class_destroy(hello_class);unregister_chrdev(major_number,DEVICE_NAME);printk(KERN_INFO"Hello:Goodbye!\n");}module_init(hello_init);module_exit(hello_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("YourName");MODULE_DESCRIPTION("SimpleHelloWorldDriver");```4.测试应用程序用户空间测试程序```c//test_hello.c#include<stdio.h>#include<stdlib.h>#include<fcntl.h>#include<unistd.h>#include<string.h>intmain(){intfd;charbuffer[100];//打开设备fd=open("/dev/hello_dev",O_RDONLY);if(fd<0){perror("Failedtoopendevice");return-1;}//读取数据if(read(fd,buffer,sizeof(buffer))<0){perror("Failedtoreadfromdevice");close(fd);return-1;}printf("Readfromdevice:%s\n",buffer);//关闭设备close(fd);return0;}```编译和测试```bash#编译驱动make#加载模块sudoinsmodhello.ko#查看内核日志dmesg|tail#创建设备节点（如果未自动创建）sudomknod/dev/hello_devc2500#250是主设备号#编译测试程序gcc-otest_hellotest_hello.c#运行测试sudo./test_hello#卸载模块sudormmodhello```5.高级驱动特性设备树支持```c//设备树匹配staticconststructof_device_idhello_of_match[]={{.compatible="company,hello-device"},{}};MODULE_DEVICE_TABLE(of,hello_of_match);//平台设备驱动staticstructplatform_driverhello_platform_driver={.probe=hello_probe,.remove=hello_remove,.driver={.name="hello-device",.of_match_table=hello_of_match,},};```IOCTL接口```c#include<linux/ioctl.h>#defineHELLO_MAGIC'x'#defineHELLO_RESET_IO(HELLO_MAGIC,0)#defineHELLO_GET_STATUS_IOR(HELLO_MAGIC,1,int)#defineHELLO_SET_DATA_IOW(HELLO_MAGIC,2,int)staticlonghello_ioctl(structfile*file,unsignedintcmd,unsignedlongarg){switch(cmd){caseHELLO_RESET:printk(KERN_INFO"Hello:Devicereset\n");break;caseHELLO_GET_STATUS://返回状态给用户空间break;caseHELLO_SET_DATA://从用户空间接收数据break;default:return-ENOTTY;}return0;}//添加到file_operationsstaticstructfile_operationsfops={.open=hello_open,.read=hello_read,.release=hello_release,.unlocked_ioctl=hello_ioctl,};```中断处理```c#include<linux/interrupt.h>staticirqreturn_thello_interrupt(intirq,void*dev_id){//处理中断printk(KERN_INFO"Hello:Interruptoccurred\n");returnIRQ_HANDLED;}//在probe函数中注册中断staticinthello_probe(structplatform_device*pdev){intirq_number;//获取中断号irq_number=platform_get_irq(pdev,0);if(irq_number<0){returnirq_number;}//注册中断处理程序returnrequest_irq(irq_number,hello_interrupt,IRQF_TRIGGER_RISING,"hello_irq",NULL);}```6.调试技巧常用调试方法```c//打印调试信息printk(KERN_DEBUG"Debugmessage:value=%d\n",value);printk(KERN_INFO"Infomessage\n");printk(KERN_WARNING"Warningmessage\n");printk(KERN_ERR"Errormessage\n");//断言BUG_ON(condition);WARN_ON(condition);//动态调试pr_debug("Debugmessagewithdynamicenable\n");```Proc文件系统接口```c#include<linux/proc_fs.h>staticinthello_proc_show(structseq_file*m,void*v){seq_printf(m,"Hellodriverstatus:\n");seq_printf(m,"Majornumber:%d\n",major_number);return0;}staticinthello_proc_open(structinode*inode,structfile*file){returnsingle_open(file,hello_proc_show,NULL);}staticconststructproc_opshello_proc_fops={.proc_open=hello_proc_open,.proc_read=seq_read,.proc_lseek=seq_lseek,.proc_release=single_release,};//在init函数中创建proc_create("hello_status",0,NULL,&hello_proc_fops);```7.最佳实践错误处理```cstaticint__inithello_init(void){intret=0;