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linux驱动开发:Linux驱动的开发1【转载】
来源: 发布时间:星期四, 2008年12月11日 浏览:9次 评论:0
| =tf width="98%" align=center border=0> | | =bw width="100%">=htd id=font_word style="FONT-SIZE: 14px; FONT-FAMILY: 宋体, Verdana, Arial, Helvetica, sans-ser ">作需要写了我们公司 块网卡 Linux驱动  经历个从无到有过程 深感技术
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oqLfbaiducukL7K交流重要Linux作为挑战微软垄断强有力武器日益受到大家喜爱真希望她能
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oqLfbaiducukL7K在中国迅速成长把文档贴出来希望和大家探讨Linux技术和应用促进Linux在
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oqLfbaiducukL7K中国普及
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oqLfbaiducukL7KLinux操作系统网络驱动编写
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oqLfbaiducukL7K.Linux系统设备驱动概述
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oqLfbaiducukL7K1.1 Linux设备驱动分类
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oqLfbaiducukL7K1.2 编写驱动些基本概念
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oqLfbaiducukL7K二.Linux系统网络设备驱动
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oqLfbaiducukL7K2.1 网络驱动结构
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oqLfbaiducukL7K2.2 网络驱动基本方法
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oqLfbaiducukL7K2.3 网络驱动中用到数据结构
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oqLfbaiducukL7K2.4 常用系统支持
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oqLfbaiducukL7K三.编写Linux网络驱动中可能遇到问题
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oqLfbaiducukL7K3.1 中断共享
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oqLfbaiducukL7K3.2 硬件发送忙时处理
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oqLfbaiducukL7K3.3 流量控制(flow control)
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oqLfbaiducukL7K3.4 调试
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oqLfbaiducukL7K四.进步阅读
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oqLfbaiducukL7K五.杂项
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oqLfbaiducukL7K.Linux系统设备驱动概述
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oqLfbaiducukL7K1.1 Linux设备驱动分类
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oqLfbaiducukL7KLinux设备驱动在Linux内核源代码中占有很大比例源代码长度日益增加
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oqLfbaiducukL7K主要是驱动增加在Linux内核不断升级过程中驱动结构还是相对稳定
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oqLfbaiducukL7K在2.0.xx到2.2.xx变动里驱动编写做了些改变但是从2.0.xx驱动到
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oqLfbaiducukL7K2.2.xx移植只需做少量工作
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oqLfbaiducukL7KLinux系统设备分为 设备(char device)块设备(block device)和网络设备(net
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oqLfbaiducukL7Kwork device)三种设备是指存取时没有缓存设备块设备读写都有缓存来支
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oqLfbaiducukL7K持并且块设备必须能够随机存取(random access)设备则没有这个要求典型
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oqLfbaiducukL7K设备包括鼠标键盘串行口等块设备主要包括硬盘软盘设备CD-ROM等个
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oqLfbaiducukL7K文件系统要安装进入操作系统必须在块设备上
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oqLfbaiducukL7K网络设备在Linux里做专门处理Linux网络系统主要是基于BSD unix 机制
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oqLfbaiducukL7K在系统和驱动之间定义有专门数据结构(sk_buff)进行数据传递系统里支持
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oqLfbaiducukL7K对发送数据和接收数据缓存提供流量控制机制提供对多协议支持
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oqLfbaiducukL7K1.2 编写驱动些基本概念
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oqLfbaiducukL7K无论是什么操作系统驱动都有些通用概念操作系统提供给驱动支
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oqLfbaiducukL7K持也大致相同下面简单介绍下网络设备驱动些基本要求
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oqLfbaiducukL7K1.2.1 发送和接收
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oqLfbaiducukL7K这是个网络设备最基本功能块网卡所做无非就是收发工作所以驱动里
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oqLfbaiducukL7K要告诉系统你发送 在哪里系统在有数据要发送时就会 你发 送还有
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oqLfbaiducukL7K驱动由于是直接操纵硬件所以网络硬件有数据收到最先能得到这个数据也就
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oqLfbaiducukL7K是驱动它负责把这些原始数据进行必要处理然后送给系统这里操作系统必
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oqLfbaiducukL7K须要提供两个机制个是找到驱动发送个是驱动把收到数据送
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oqLfbaiducukL7K给系统
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oqLfbaiducukL7K1.2.2 中断
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oqLfbaiducukL7K中断在现代计算机结构中有重要地位操作系统必须提供驱动响应中断能力
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oqLfbaiducukL7K般是把个中断处理注册到系统中去操作系统在硬件中断发生后 驱动
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oqLfbaiducukL7K处理Linux支持中断共享即多个设备共享个中断
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oqLfbaiducukL7K1.2.3 时钟
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oqLfbaiducukL7K在实现驱动时很多地方会用到时钟如某些协议里超时处理没有中断机制
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oqLfbaiducukL7K硬件轮询等操作系统应为驱动提供定时机制般是在预定时 间过了以后回
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oqLfbaiducukL7K调注册时钟在网络驱动中如果硬件没有中断功能定时器可以提供轮询
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oqLfbaiducukL7K(poll)方式对硬件进行存取或者是实现某些协议时需要超时重传等
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oqLfbaiducukL7K二.Linux系统网络设备驱动
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oqLfbaiducukL7K2.1 网络驱动结构
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oqLfbaiducukL7K所有Linux网络驱动遵循通用接口设计时采用是面向对象方法个设备
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oqLfbaiducukL7K就是个对象(device 结构)它内部有自己数据和方法每个设备方法被时
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oqLfbaiducukL7K第个参数都是这个设备对象本身这样这个方法就可以存取自身数据(类似面向对
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oqLfbaiducukL7K象设计时this引用)
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oqLfbaiducukL7K个网络设备最基本方法有 化、发送和接收
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oqLfbaiducukL7K------------------- ---------------------
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oqLfbaiducukL7K|deliver packets | |receive packets queue|
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oqLfbaiducukL7K|(dev_queue_xmit ) | |them(net_rx) |
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oqLfbaiducukL7K------------------- ---------------------
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oqLfbaiducukL7K| | /
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oqLfbaiducukL7K/ | |
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oqLfbaiducukL7K-------------------------------------------------------
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oqLfbaiducukL7K| methods and variables(initialize,open,close,hard_xmit,|
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oqLfbaiducukL7K|  errupt handler,config,resources,status...) |
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oqLfbaiducukL7K-------------------------------------------------------
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oqLfbaiducukL7K| | /
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oqLfbaiducukL7K/ | |
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oqLfbaiducukL7K----------------- ----------------------
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oqLfbaiducukL7K|send to hardware | |receivce from hardware|
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oqLfbaiducukL7K----------------- ----------------------
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oqLfbaiducukL7K| | /
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oqLfbaiducukL7K/ | |
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oqLfbaiducukL7K-----------------------------------------------------
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oqLfbaiducukL7K| hardware media |
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oqLfbaiducukL7K-----------------------------------------------------
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oqLfbaiducukL7K化完成硬件化、device中变量化和系统资源申请发送是
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oqLfbaiducukL7K在驱动上层协议层有数据要发送时自动般驱动中不对发送数据进
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oqLfbaiducukL7K行缓存而是直接使用硬件发送功能把数据发送出去接收数据般是通过硬件中断
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oqLfbaiducukL7K来通知在中断处理里把硬件帧信息填入个skbuff结构中然后net_
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oqLfbaiducukL7Krx传递给上层处理
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oqLfbaiducukL7K2.2 网络驱动基本方法
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oqLfbaiducukL7K网络设备做为个对象提供些方法供系统访问正是这些有统接口方法掩蔽
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oqLfbaiducukL7K了硬件具体细节让系统对各种网络设备访问都采用统形式做到硬件无关性
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oqLfbaiducukL7K
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oqLfbaiducukL7K下面解释最基本方法
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oqLfbaiducukL7K2.2.1 化(initialize)
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oqLfbaiducukL7K驱动必须有个化方法在把驱动载入系统时候会这个化
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oqLfbaiducukL7K它做以下几方面工作检测设备在化里你可以根据硬件特征检查硬件
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oqLfbaiducukL7K是否存在然后决定是否启动这个驱动配置和化硬件在化里你可
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oqLfbaiducukL7K以完成对硬件资源配置比如即插即用硬件就可以在这个时候进行配置(Linux内核
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oqLfbaiducukL7K对PnP功能没有很好支持可以在驱动里完成这个功能)配置或协商好硬件占用
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oqLfbaiducukL7K资源以后就可以向系统申请这些资源有些资源是可以和别设备共享如中断
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oqLfbaiducukL7K有些是不能共享如IO、DMA接下来你要化device结构中变量最后你可
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oqLfbaiducukL7K以让硬件正式开始工作
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oqLfbaiducukL7K2.2.2 打开(open)
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oqLfbaiducukL7Kopen这个方法在网络设备驱动里是网络设备被激活时候被(即设备状态由dow
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oqLfbaiducukL7Kn-->up)所以实际上很多在initialize中工作可以放到这里来做比如资源申请
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oqLfbaiducukL7K硬件激活如果dev->open返回非0(error)则硬件状态还是down
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oqLfbaiducukL7Kopen方法另个作用是如果驱动做为个模块被装入则要防止模块卸载时设备处
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oqLfbaiducukL7K于打开状态在open方法里要MOD_INC_USE_COUNT宏
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oqLfbaiducukL7K2.2.3 关闭(stop)
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oqLfbaiducukL7Kclose方法做和open相反工作可以释放某些资源以减少系统负担close是在设备状
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oqLfbaiducukL7K态由up转为down时被另外如果是做为模块装入驱动close里应该M
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oqLfbaiducukL7KOD_DEC_USE_COUNT减少设备被引用次数以使驱动可以被卸载
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oqLfbaiducukL7K另外close方法必须返回成功(0 success)
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oqLfbaiducukL7K2.2.4 发送(hard_start_xmit)
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oqLfbaiducukL7K所有网络设备驱动都必须有这个发送方法在系统驱动xmit时发送
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oqLfbaiducukL7K数据放在个sk_buff结构中般驱动把数据传给硬件发出去也有些特殊
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oqLfbaiducukL7K设备比如loopback把数据组成个接收数据再回送给系统或者dummy设备直接丢弃数
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oqLfbaiducukL7K据
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oqLfbaiducukL7K如果发送成功hard_start_xmit方法里释放sk_buff返回0(发送成功)如果设备暂时
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oqLfbaiducukL7K无法处理比如硬件忙则返回1这时如果dev->tbusy置为非0则系统认为硬件忙
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oqLfbaiducukL7K要等到dev->tbusy置0以后才会再次发送tbusy置0任务般由中断完成硬件在发送
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oqLfbaiducukL7K结束后产生中断这时可以把tbusy置0然后用mark_bh通知系统可以再次发送
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oqLfbaiducukL7K在发送不成功情况下也可以不置dev->tbusy为非0这样系统会不断尝试重发如果
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oqLfbaiducukL7Khard_start_xmit发送不成功则不要释放sk_buff传送下来sk_buff中数据已经包
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oqLfbaiducukL7K含硬件需要帧头所以在发送方法里不需要再填充硬件帧头数据可以直接提交给硬
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oqLfbaiducukL7K件发送sk_buff是被锁住(locked)确保其他不会存取它
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oqLfbaiducukL7K2.2.5 接收(reception)
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oqLfbaiducukL7K驱动并不存在个接收方法有数据收到应该是驱动来通知系统般设备
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oqLfbaiducukL7K收到数据后都会产生个中断在中断处理中驱动申请块sk_buff(skb)从
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oqLfbaiducukL7K硬件读出数据放置到申请好缓冲区里接下来填充sk_buff中 些信息skb->dev
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oqLfbaiducukL7K = dev判断收到帧协议类型填入skb->protocol(多协 议支持)把指针skb->m
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oqLfbaiducukL7Kac.raw指向硬件数据然后丢弃硬件帧头(skb_pull)还要设置skb->pkt_type标明第二
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oqLfbaiducukL7K层(链路层)数据类型可以是以下类型：
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oqLfbaiducukL7KPACKET_BROADCAST : 链路层广播
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oqLfbaiducukL7KPACKET_MULTICAST : 链路层组播
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oqLfbaiducukL7KPACKET_SELF : 发给自己帧
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oqLfbaiducukL7KPACKET_OTHERHOST : 发给别人帧(监听模式时会有这种帧)
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oqLfbaiducukL7K最后net_rx把数据传送给协议层net_rx里数据放入处理队列然后返回
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oqLfbaiducukL7K真正处理是在中断返回以后这样可以减少中断时间net_rx以后
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oqLfbaiducukL7K驱动就不能再存取数据缓冲区skb
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oqLfbaiducukL7K2.2.6 硬件帧头(hard_header)
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oqLfbaiducukL7K硬件般都会在上层数据发送之前加上自己硬件帧头比如以太网(Ethernet)就有14
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oqLfbaiducukL7K字节帧头这个帧头是加在上层ip、ipx等数据包前面驱动提供个hard_
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oqLfbaiducukL7Kheader方法协议层(ip、ipx、arp等)在发送数据之前会这段
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oqLfbaiducukL7K硬件帧头长度必须填在dev->hard_header_len这样协议层回在数据之前保留好硬件
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oqLfbaiducukL7K帧头空间这样hard_header只要skb_push然后正确填入硬件帧头就可以了
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oqLfbaiducukL7K
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oqLfbaiducukL7K在协议层hard_header时传送参数包括(2.0.xx)：数据sk_buffdevice指针
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oqLfbaiducukL7Kprotocol目地址(daddr)源地址(saddr)数据长度(len)数据长度不要使用s
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oqLfbaiducukL7Kk_buff中参数 hard_header时数据可能还没完全组织好saddr是NULL话
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oqLfbaiducukL7K是使用缺省地址(default)daddr是NULL表明协议层不知道硬件目地址如果hard_h
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oqLfbaiducukL7Keader完全填好了硬件帧头则返回添加字节数如果硬件帧头中信息还不完全(比
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oqLfbaiducukL7K如daddr为NULL但是帧头中需要目硬件地址典型情况是以太网需要地址解析(ar
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oqLfbaiducukL7Kp))则返回负字节数hard_header返回负数情况下协议层会做进步build he
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oqLfbaiducukL7Kader工作目前Linux系统里就是做arp (如果hard_header返回正dev->arp=1表明
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oqLfbaiducukL7K不需要做arp返回负dev->arp=0做arp)
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oqLfbaiducukL7K对hard_header在每个协议层处理里如ip_output
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oqLfbaiducukL7K2.2.7 地址解析(xarp)
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oqLfbaiducukL7K有些网络有硬件地址(比如Ethernet)并且在发送硬件帧时需要知道目硬件地址这
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oqLfbaiducukL7K样就需要上层协议地址(ip、ipx)和硬件地址对应这个对应是通过地址解析完成
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oqLfbaiducukL7K需要做arp设备在发送之前会驱动rebuild_header方法主要参数
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oqLfbaiducukL7K包括指向硬件帧头指针协议层地址如果驱动能够解析硬件地址就返回1如
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oqLfbaiducukL7K果不能返回0
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oqLfbaiducukL7K对rebuild_header在net/core/dev.cdo_dev_queue_xmit里
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oqLfbaiducukL7K2.2.8 参数设置和统计数据
oqLfbaiducukL7K
oqLfbaiducukL7K在驱动里还提供些方法供系统对设备参数进行设置和读取信息般只有超级
oqLfbaiducukL7K
oqLfbaiducukL7K用户(root)权限才能对设备参数进行设置设置方法有：
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oqLfbaiducukL7Kdev-> _mac_address
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oqLfbaiducukL7K当用户ioctl类型为SIOCSIFHWADDR时是要设置这个设备mac地址般对mac地址
oqLfbaiducukL7K
oqLfbaiducukL7K设置没有太大意义
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oqLfbaiducukL7Kdev->_config
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oqLfbaiducukL7K当用户ioctl时类型为SIOCSIFMAP时系统会驱动_config方法用户
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oqLfbaiducukL7K会传递个map结构包含需要I/O、中断等参数
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oqLfbaiducukL7Kdev->do_ioctl
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oqLfbaiducukL7K如果用户ioctl时类型在SIOCDEVPRIVATE和SIOCDEVPRIVATE+15之间系统会驱
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oqLfbaiducukL7K动这个方法般是设置设备专用数据
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oqLfbaiducukL7K读取信息也是通过ioctl进行除次之外驱动还可以提供个
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oqLfbaiducukL7Kdev->get_stats方法返回个enet_statistics结构包含发送接收统计信息ioc
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oqLfbaiducukL7Ktl处理在net/core/dev.cdev_ioctl和dev_sioc里
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