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原文地址:我对linux的理解之device_register 作者:amingriyue ------------------------------------------ 本文系本站原创,欢迎转载! 转载请注明出处:amingriyue.blog.chinaunix.net ------------------------------------------/** * device_register - register a device with the system. * @dev: pointer to the device structure * * This happens in two clean steps - initialize the device * and add it to the system. The two steps can be called * separately, but this is the easiest and most common. * I.e. you should only call the two helpers separately if * have a clearly defined need to use and refcount the device * before it is added to the hierarchy. * * NOTE: _Never_ directly free @dev after calling this function, even * if it returned an error! Always use put_device() to give up the * reference initialized in this function instead. */int device_register(struct device *dev){ device_initialize(dev); //初始化dev,见第1部分分析 return device_add(dev); //添加设备,这是device_register的主要工作,见第2部分分析}函数定义很简洁,第一步初始化dev,第二步添加设备。我们也分两部分进行分析: 1,device_initialize()
void device_initialize(struct device *dev){ dev->kobj.kset = devices_kset; //devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL),即devices_kset代表了/sys/devices/ kobject_init(&dev->kobj, &device_ktype); //初始化dev的kobj,这个函数在driver_register中分析过了 INIT_LIST_HEAD(&dev->dma_pools); //初始化dev的内存池的列表 init_MUTEX(&dev->sem); //初始化信号量 spin_lock_init(&dev->devres_lock); //初始化自旋锁 INIT_LIST_HEAD(&dev->devres_head); //初始化队列头 device_init_wakeup(dev, 0); //由其定义知初始化dev->power.can_wakeup = dev->power.should_wakeup = 0; device_pm_init(dev); //初始化dev->power.status = DPM_ON; set_dev_node(dev, -1); //如果配置了numa,设置dev->numa_node = -1; numa是非统一内存访问架构,一般用于服务器中,所以一般嵌入式中不使用。}这个dev的初始化主要是设置dev结构中的各个变量等以及对kobj的相关操作。 2,device_add()
int device_add(struct device *dev){ struct device *parent = NULL; struct class_interface *class_intf; int error = -EINVAL; dev = get_device(dev); //主要是增加dev->kobj->kref的引用 if (!dev) goto done; dev->p = kzalloc(sizeof(*dev->p), GFP_KERNEL); //这里p是dev中的device_private结构,跟驱动的driver_private相似 if (!dev->p) { error = -ENOMEM; goto done; } dev->p->device = dev; //将dev赋值给p的device保存 klist_init(&dev->p->klist_children, klist_children_get, klist_children_put); //初始化p的klist_children /* * for statically allocated devices, which should all be converted * some day, we need to initialize the name. We prevent reading back * the name, and force the use of dev_name() */ if (dev->init_name) { dev_set_name(dev, "%s", dev->init_name); dev->init_name = NULL; } if (!dev_name(dev)) goto name_error; pr_debug("device: '%s': %s\n", dev_name(dev), __func__); parent = get_device(dev->parent); //得到父设备 setup_parent(dev, parent); /* use parent numa_node */ if (parent) set_dev_node(dev, dev_to_node(parent)); //不使用numa /* first, register with generic layer. */ /* we require the name to be set before, and pass NULL */ error = kobject_add(&dev->kobj, dev->kobj.parent, NULL); //这个函数在driver_register中分析过了,主要将kobj添加到sys的层次中 if (error) goto Error; /* notify platform of device entry */ if (platform_notify) platform_notify(dev); error = device_create_file(dev, &uevent_attr); //在driver_register中已经分析,主要是在/sys/devices/.../中添加dev的uevent属性文件 if (error) goto attrError; if (MAJOR(dev->devt)) { error = device_create_file(dev, &devt_attr); //主要是在sys/devices/...中添加dev属性文件 if (error) goto ueventattrError; error = device_create_sys_dev_entry(dev); //在/sys/dev/char/或者/sys/dev/block/创建devt的属性的连接文件,形如10:45,由主设备号和次设备号构成,指向/sys/devices/.../的具体设备目录,该链接文件只具备读属性,显示主设备号:次设备号,如10:45,用户空间udev相应uevent事件时,将根据设备号在/dev下创建节点文件 if (error) goto devtattrError; } error = device_add_class_symlinks(dev); //相互创建dev和class之间的链接文件 if (error) goto SymlinkError; error = device_add_attrs(dev); //添加设备属性文件 if (error) goto AttrsError; error = bus_add_device(dev); //将设备添加到bus上,创建subsystem链接文件,链接class下的具体的子系统文件夹 if (error) goto BusError; error = dpm_sysfs_add(dev); //添加设备的电源管理属性,截止这里,我们的/sys/devices/.../具体设备目录下至少生成有以下四个属性文件:uevent,dev,subsystem,power,你找到了吗? if (error) goto DPMError; device_pm_add(dev); //添加设备到激活设备列表中,用于电源管理 /* Notify clients of device addition. This call must come * after dpm_sysf_add() and before kobject_uevent(). */ if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_ADD_DEVICE, dev);//执行bus通知链上的注册函数,由设备注册上来 kobject_uevent(&dev->kobj, KOBJ_ADD); //产生一个KOBJ_ADD的uevent事件,通过netlink机制和用户空间通信,这个driver_register中已经分析过了 bus_probe_device(dev); //去bus上找dev对应的drv,主要执行__device_attach,主要进行match,sys_add,执行probe函数和绑定等操作 if (parent) klist_add_tail(&dev->p->knode_parent, &parent->p->klist_children); //把设备添加到父设备的children列表中 if (dev->class) { //如果改dev有所属类,则将dev的添加到类的设备列表里面 mutex_lock(&dev->class->p->class_mutex); /* tie the class to the device */ klist_add_tail(&dev->knode_class, &dev->class->p->class_devices); /* notify any interfaces that the device is here */ list_for_each_entry(class_intf, &dev->class->p->class_interfaces, node) if (class_intf->add_dev) //执行改dev的class_intf->add_dev(),这个有个好处,就是只有设备匹配注册成功了,才进行其它的注册工作(如字符设备的注册,生成/dev/***节点文件)以及部分初始化工作。 class_intf->add_dev(dev, class_intf); mutex_unlock(&dev->class->p->class_mutex); }done: put_device(dev); return error; DPMError: bus_remove_device(dev); BusError: device_remove_attrs(dev); AttrsError: device_remove_class_symlinks(dev); SymlinkError: if (MAJOR(dev->devt)) device_remove_sys_dev_entry(dev); devtattrError: if (MAJOR(dev->devt)) device_remove_file(dev, &devt_attr); ueventattrError: device_remove_file(dev, &uevent_attr); attrError: kobject_uevent(&dev->kobj, KOBJ_REMOVE); kobject_del(&dev->kobj); Error: cleanup_device_parent(dev); if (parent) put_device(parent);name_error: kfree(dev->p); dev->p = NULL; goto done;}这部分是device_register的主要工作,我们这里就不在详细分析了,相信有了driver_register分析的基础,这部分分析工作应该会变得很轻松~