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转载请注明出处:amingriyue.blog. ------------------------------------------/** * driver_register - register driver with bus * @drv: driver to register * * We pass off most of the work to the bus_add_driver() call, * since most of the things we have to do deal with the bus * structures. * driver_register - 注册驱动到bus * @drv: 要注册的驱动 * * 我们把很多工作都放到bus_add_driver()中,因为我们要做的大部分事情都跟bus结构有关系 */ 我们首先来完整地看下driver_register函数定义： int driver_register(struct device_driver *drv) { int ret; struct device_driver *other; BUG_ON(!drv->bus->p); //判断bus->p是否为空，见第1部分分析 if ((drv->bus->probe && drv->probe) || //判断驱动跟驱动的总线是否有冲突的函数注册，给出警告信息，见第2部分分析 (drv->bus->remove && drv->remove) || (drv->bus->shutdown && drv->shutdown)) printk(KERN_WARNING "Driver '%s' needs updating - please use " "bus_type methods\n", drv->name); other = driver_find(drv->name, drv->bus); //在注册在bus上的driver寻找是否有跟要注册的driver相同，有则表明驱动已被注册过，见第3部分分析 if (other) { put_driver(other); printk(KERN_ERR "Error: Driver '%s' is already registered, " "aborting...\n", drv->name); return -EBUSY; } ret = bus_add_driver(drv); //经过上面的验证后，将驱动添加注册到bus上，见第4部分分析 if (ret) return ret; ret = driver_add_groups(drv, drv->groups); //如果grop不为空的话，将在驱动文件夹下创建以group名字的子文件夹，然后在子文件夹下添加group的属性文件 if (ret) bus_remove_driver(drv); return ret; } 这个函数开始先判断bus->p是否为空，如果不为空然后判断驱动跟驱动的总线是否有冲突的函数注册，如果有冲突就给出警告信息，然后在注册在bus上的driver寻找是否有跟 要注册的driver相同，有则表明驱动已被注册过，返回错误。经过上面的验证后，将驱动添加注册到bus上，如果没问题，则再将驱动添加到同一属性的组中，在sysfs下表现为同一个目录。 有了大概的流程概念后，我们开始一步一步的详细分析，分为四个部分： 1，BUG_ON(!drv->bus->p); BUG_ON定义如下： #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); } while(0) 其中的BUG()： #define BUG() do { \ printk("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \ panic("BUG!"); \ } while (0) 由上面定义可以看出，如果drv->bus->p为空，则打印失败信息以及panic信息。其实这个主要是判断bus是否存在,这个结论还需要论证！ 2， if ((drv->bus->probe && drv->probe) || (drv->bus->remove && drv->remove) || (drv->bus->shutdown && drv->shutdown)) printk(KERN_WARNING "Driver '%s' needs updating - please use " "bus_type methods\n", drv->name); 主要是判断驱动跟驱动的总线是否有冲突的函数注册，给出警告信息 3，other = driver_find(drv->name, drv->bus) driver_find()函数定义如下： struct device_driver *driver_find(const char *name, struct bus_type *bus) { struct kobject *k = kset_find_obj(bus->p->drivers_kset, name);//在bus的驱动集合里面发现同名自动的驱动 struct driver_private *priv; if (k) { priv = to_driver(k);//如果找到，通过kobject转换成driver_private，返回相应的驱动 return priv->driver; } return NULL; } 这个函数的功能就是查找bus上已经注册的驱动，和要注册的驱动比较，如果找到，则返回找到的驱动。bus->p->drivers_kset是bus上已经注册的驱动的kobject的结合，会传给kset_find_obj()作为参数。 读到这里，应该去复习一下kobject,kset,sysfs等概念了。这里为了分析的连贯性就不再插入相关概念。 3-1：kset_find_obj()的定义如下： struct kobject *kset_find_obj(struct kset *kset, const char *name) { struct kobject *k; struct kobject *ret = NULL; spin_lock(&kset->list_lock); list_for_each_entry(k, &kset->list, entry) { //遍历kset->list中的每个kobject if (kobject_name(k) && !strcmp(kobject_name(k), name)) { ret = kobject_get(k); //若有同名字的，增加kobject的kref，并返回该kobject break; } } spin_unlock(&kset->list_lock); return ret; } 它会查找在kset->list上的每一个kobject与改驱动的名字是否有同名字的，如果找到则返回改kobject。 4，bus_add_driver(drv); 它的定义如下： int bus_add_driver(struct device_driver *drv) { struct bus_type *bus; struct driver_private *priv; int error = 0; bus = bus_get(drv->bus); //找到该drv所属的bus，其实就是增加该bus->p->subsys->kobject->kref的引用计数 if (!bus) return -EINVAL; pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name); priv = kzalloc(sizeof(*priv), GFP_KERNEL); //分配driver_private结构 if (!priv) { error = -ENOMEM; goto out_put_bus; } klist_init(&priv->klist_devices, NULL, NULL); //初始化priv->klist_devices priv->driver = drv; //将该drv赋值给priv->driver drv->p = priv; //而drv的drv->p又等于priv priv->kobj.kset = bus->p->drivers_kset; //指向bus的drvier容器 error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,"%s", drv->name); //驱动的kobject初始化和添加dir到sysfs中，后面会有分析，见4-1部分 if (error) goto out_unregister; if (drv->bus->p->drivers_autoprobe) { //这个变量默认是为1的 error = driver_attach(drv); //匹配函数，后面会分析，见4-2部分 if (error) goto out_unregister; } klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); //将priv->knode_bus添加到bus->p->klist_drivers，见4-3部分 module_add_driver(drv->owner, drv); //添加drv的module，见4-4部分 error = driver_create_file(drv, &driver_attr_uevent); //在sysfs的目录下创建文件uevent属性文件，见4-5分析 if (error) { printk(KERN_ERR "%s: uevent attr (%s) failed\n",__func__, drv->name); } error = driver_add_attrs(bus, drv); //给driver添加bus上的所有属性 if (error) { /* How the hell do we get out of this pickle? Give up */ printk(KERN_ERR "%s: driver_add_attrs(%s) failed\n",__func__, drv->name); } error = add_bind_files(drv);
//添加绑定文件，driver_attr_bind 和 driver_attr_unbind 见4-5分析 if (error) { /* Ditto */ printk(KERN_ERR "%s: add_bind_files(%s) failed\n",__func__, drv->name); } kobject_uevent(&priv->kobj, KOBJ_ADD); //产生一个KOBJ_ADD uevent return 0; out_unregister: kfree(drv->p); drv->p = NULL; kobject_put(&priv->kobj); out_put_bus: bus_put(bus); return error; } 这个函数是driver_register中核心函数，真正的功能实现都在这个函数里面。这个函数首先找到该drv所属的bus，然后为driver_private结构分配空间， 然后初始化priv，把driver，bus，priv联系在一块，然后添加驱动的kobject到kobject的层次中，也就是添加驱动文件夹到sysfs，然后根据drivers_autoprobe决定是否去bus上寻找与driver匹配的device。 然后将driver添加到bus上的驱动列表中。然后添加驱动的模块，再然后就是生成sysfs下面的一些属性文件。 4-1，kobject_init_and_add() int kobject_init_and_add(struct kobject *kobj, struct kobj_type *ktype, struct kobject *parent, const char *fmt, ...) { va_list args; int retval; kobject_init(kobj, ktype); //初始化kobject 4-1-1 va_start(args, fmt); //动态可变参数的使用 retval = kobject_add_varg(kobj, parent, fmt, args); // 4-1-2 va_end(args); return retval; } 4-1-1，kobject_init() void kobject_init(struct kobject *kobj, struct kobj_type *ktype) { ... kobject_init_internal(kobj); // 4-1-1-1 kobj->ktype = ktype; ... } kobject_init将调用kobject_init_internal() 4-1-1-1,kobject_init_internal() static void kobject_init_internal(struct kobject *kobj) { if (!kobj) return; kref_init(&kobj->kref); //原子地将kobj->kref设为1 INIT_LIST_HEAD(&kobj->entry); //初始化kobj->entry列表 kobj->state_in_sysfs = 0; kobj->state_add_uevent_sent = 0; kobj->state_remove_uevent_sent = 0; kobj->state_initialized = 1; } 可以看出kobject_init()的功能就是初始化kobject结构中的成员状态。 4-1-2，这里我们不介绍动态变量的使用方法，开始分析kobject_add_varg() static int kobject_add_varg(struct kobject *kobj, struct kobject *parent, const char *fmt, va_list vargs) { int retval; retval = kobject_set_name_vargs(kobj, fmt, vargs); //主要是将vargs按照fmt格式给kobject起个名字，从调用关系知道vargs是drv->name，也就是驱动的名字 if (retval) { printk(KERN_ERR "kobject: can not set name properly!\n"); return retval; } kobj->parent = parent; //由上面的函数调用关系可以知道这个将被赋值为NULL return kobject_add_internal(kobj); //见 4-1-2-1 } 4-1-2-1，kobject_add_internal() static int kobject_add_internal(struct kobject *kobj) { ... parent = kobject_get(kobj->parent); //得到父节点，从上面知道parent是NULL /* join kset if set, use it as parent if we do not already have one */ if (kobj->kset) { //kset不为空 if (!parent) //parent为空 parent = kobject_get(&kobj->kset->kobj); kobj_kset_join(kobj); kobj->parent = parent; /*如果kset不为空，而parent为空(这里这个条件一定成立的，因为kset=bus->p->drivers_kset，parent=NULL)， 则该kobj->parent指向kobj->kset->kobj，而且将kobj加入到kobj->kset的list中，也就是driver放入bus的kset列表中，也就是bus是driver的容器，实际上bus同时还是device的容器，当 然bu s本身实质上也是个kobject，所以理解kset这个容器的概念至关重要，它是构成了sysfs的层次结构关系*/ } pr_debug("kobject: '%s' (%p): %s: parent: '%s', set: '%s'\n", kobject_name(kobj), kobj, __func__,parent ? kobject_name(parent) : "<NULL>", kobj->kset ? kobject_name(&kobj->kset->kobj) : "<NULL>"); error = create_dir(kobj); //建立该驱动的文件夹，见4-2-1-1分析 if (error) { kobj_kset_leave(kobj); kobject_put(parent); kobj->parent = NULL; /* be noisy on error issues */ if (error == -EEXIST) printk(KERN_ERR "%s failed for %s with ""-EEXIST, don't try to register things with " "the same name in the same directory.\n", __func__, kobject_name(kobj)); else printk(KERN_ERR "%s failed for %s (%d)\n",__func__, kobject_name(kobj), error); dump_stack(); } else kobj->state_in_sysfs = 1; return error; } 这个函数主要设置drvier的kobject和bus之间的层次关系，然后在sysfs中建立该驱动的文件夹 4-1-2-1-1，create_dir() static int create_dir(struct kobject *kobj) { int error = 0; if (kobject_name(kobj)) { error = sysfs_create_dir(kobj); //创建该kobj（driver的）文件夹，见 4-1-2-1-1-1 if (!error) { error = populate_dir(kobj); if (error) sysfs_remove_dir(kobj); } } return error; } 4-1-2-1-1-1，sysfs_create_dir int sysfs_create_dir(struct kobject * kobj) { struct sysfs_dirent *parent_sd, *sd; //sysfs层次结构的基石 int error = 0; BUG_ON(!kobj); if (kobj->parent) //到这步驱动的kobj->parent是bus->p->drivers_kset parent_sd = kobj->parent->sd; //bus->p->drivers_kset的目录 else parent_sd = &sysfs_root; //否则添加到sys的根目录下，即/sys/ error = create_dir(kobj, parent_sd, kobject_name(kobj), &sd); //在bus->p->drivers_kset的文件夹下创建该驱动的文件夹 if (!error) kobj->sd = sd; return error; } 说到这里，可能一直感觉很空洞，很抽象，拿i2c总线举个例子吧，i2c总线注册好后将会有如下文件夹结构/sys/bus/i2c/，在/sys/bus/i2c/文件夹下会有如下文件夹uevent devices、drivers、drivers_probe、drivers_autoprobe，当你注册驱动的时候，将会在/sys/bus/i2c/drivers/下注册一个改驱动的文件夹，比如ov7675，那么它将会注册成 /sys/bus/i2c/drivers/ov7675/，其实这些文件夹都对应一个kobject,通过kset容器组成一个很清晰的层次结构。经过漫长的过程我们分析完了kobject_init_and_add(),我们下面进入 4-2部分driver_attach进行分析。这也是一个非常重要的函数，好吧，开始我们的又一个漫长之旅吧！ 4-2,driver_attach() 定义如下： int driver_attach(struct device_driver *drv) { return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach); } 该函数将调用bus_for_each_dev()。 4-2-1，bus_for_each_dev() int bus_for_each_dev(struct bus_type *bus, struct device *start,void *data, int (*fn)(struct device *, void *)) // 4-2-1-1 __driver_attach { struct klist_iter i; struct device *dev; int error = 0; if (!bus) return -EINVAL; klist_iter_init_node(&bus->p->klist_devices, &i,(start ? &start->p->knode_bus : NULL)); //将bus中的已注册的device列表放到迭代器中，方便索引 while ((dev = next_device(&i)) && !error) //将驱动逐个地与列表中每一个的device匹配，可能一个驱动匹配好几个设备 error = fn(dev, data); //这个fn就是上面传下来的__driver_attach klist_iter_exit(&i); return error; } 4-2-1-1，__driver_attach static int __driver_attach(struct device *dev, void *data) { struct device_driver *drv = data; /* * Lock device and try to bind to it. We drop the error * here and always return 0, because we need to keep trying * to bind to devices and some drivers will return an error * simply if it didn't support the device. * * driver_probe_device() will spit a warning if there * is an error. */ if (!driver_match_device(drv, dev)) //跟名字的意思一样，driver跟device尝试匹配 return 0; if (dev->parent) /* Needed for USB */ down(&dev->parent->sem); down(&dev->sem); if (!dev->driver) driver_probe_device(drv, dev); // 4-2-1-1-2 up(&dev->sem); if (dev->parent) up(&dev->parent->sem); return 0; } 4-2-1-1-1，driver_match_device() static inline int driver_match_device(struct device_driver *drv, struct device *dev) { return drv->bus->match ? drv->bus->match(dev, drv) : 1; } 这里看bus的总线的match函数是否已经注册，如果没注册则直接返回1，如果注册，则调用注册的匹配函数。同样，以i2c总线为例吧， struct bus_type i2c_bus_type = { .name = "i2c", .dev_attrs = i2c_dev_attrs, .match = i2c_device_match, ... }; static int i2c_device_match(struct device *dev, struct device_driver *drv) { struct i2c_client *client = to_i2c_client(dev); struct i2c_driver *driver = to_i2c_driver(drv); /* match on an id table if there is one */ if (driver->id_table) return i2c_match_id(driver->id_table, client) != NULL;//只匹配id的名字和client的名字,跟驱动的名字没有关系,注意这里的client是设备转换过来,而不是设备的本身 return 0; } 转而调用i2c_match_id(); static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id, const struct i2c_client *client) { while (id->name[0]) { if (strcmp(client->name, id->name) == 0) //匹配设备client名字和id_table中的名字 return id; id++; } return NULL; } 所以i2c总线根据设备client名字和id_table中的名字进行匹配的。如果匹配了，则返回id值，在i2c_device_match中则返回真。也就是bus的match函数将会返回真。那将会进入driver_probe_device()。 4-2-1-1-2，driver_probe_device() int driver_probe_device(struct device_driver *drv, struct device *dev) { int ret = 0; if (!device_is_registered(dev)) //首先判断这个device是否已经注册 return -ENODEV; pr_debug("bus: '%s': %s: matched device %s with driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name); ret = really_probe(dev, drv); //转而调用really_probe() return ret; } 4-2-1-1-2-1,really_probe() static atomic_t probe_count = ATOMIC_INIT(0); //记录probe数目 static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue); //probe队列 static int really_probe(struct device *dev, struct device_driver *drv) { int ret = 0; atomic_inc(&probe_count); //原子增加计数 pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev)); WARN_ON(!list_empty(&dev->devres_head)); dev->driver = drv; //把驱动赋值给dev->drvier if (driver_sysfs_add(dev)) { //主要是添加driver和dev之间的连接文件，见4-2-1-1-2-1-1分析 printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n", __func__, dev_name(dev)); goto probe_failed; } if (dev->bus->probe) { //如果bus的probe注册将执行，否则执行driver的probe，这也是函数开始时检测的原因！ ret = dev->bus->probe(dev); if (ret) goto probe_failed; } else if (drv->probe) { ret = drv->probe(dev); if (ret) goto probe_failed; } driver_bound(dev); //driver绑定dev，见4-2-1-1-2-1-2分析 ret = 1; pr_debug("bus: '%s': %s: bound device %s to driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name); goto done; probe_failed: devres_release_all(dev); driver_sysfs_remove(dev); dev->driver = NULL; if (ret != -ENODEV && ret != -ENXIO) { /* driver matched but the probe failed */ printk(KERN_WARNING "%s: probe of %s failed with error %d\n", drv->name, dev_name(dev), ret); } /* * Ignore errors returned by ->probe so that the next driver can try * its luck. */ ret = 0; done: atomic_dec(&probe_count); wake_up(&probe_waitqueue); return ret; } 4-2-1-1-2-1-1，driver_sysfs_add static int driver_sysfs_add(struct device *dev) { int ret; ret = sysfs_create_link(&dev->driver->p->kobj, &dev->kobj, kobject_name(&dev->kobj)); //在driver目录下添加以dev->kobj名字的连接文件，连接到device if (ret == 0) { ret = sysfs_create_link(&dev->kobj, &dev->driver->p->kobj, "driver"); //同样在device目录下添加'driver’为名字的连接文件连接到drvier if (ret) sysfs_remove_link(&dev->driver->p->kobj, kobject_name(&dev->kobj)); } return ret; } 4-2-1-1-2-1-2，driver_bound() static void driver_bound(struct device *dev) { if (klist_node_attached(&dev->p->knode_driver)) { //查看是否已经绑定 printk(KERN_WARNING "%s: device %s already bound\n", __func__, kobject_name(&dev->kobj)); return; } pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev), __func__, dev->driver->name); if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_BOUND_DRIVER, dev); //调用注册bus通知链上的所有函数 klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); //将设备的驱动node添加到diver的klist_devices中.定义同4-3部分 } 4-3，klist_add_tail() 定义如下： void klist_add_tail(struct klist_node *n, struct klist *k) { klist_node_init(k, n); //初始化一个klist_node,并将klist联系起来 add_tail(k, n); //将n添加到k的末尾 } 4-4，module_add_driver() void module_add_driver(struct module *mod, struct device_driver *drv) { char *driver_name; int no_warn; struct module_kobject *mk = NULL; if (!drv) return; if (mod) //一般情况下为THIS_MODULE mk = &mod->mkobj; else if (drv->mod_name) { //如果没模块，则检查驱动的模块名 struct kobject *mkobj; /* Lookup built-in module entry in /sys/modules */ mkobj = kset_find_obj(module_kset, drv->mod_name); //根据驱动模块的名字去module_kset集合中找 if (mkobj) { mk = container_of(mkobj, struct module_kobject, kobj); //用container_of方法通过kobj转换成module_kobject /* remember our module structure */ drv->p->mkobj = mk; //赋值给驱动的mkobj /* kset_find_obj took a reference */ kobject_put(mkobj); } } if (!mk) //mk如果为null则返回 return; /* Don't check return codes; these calls are idempotent */ no_warn = sysfs_create_link(&drv->p->kobj, &mk->kobj, "module"); //在驱动文件夹下创建名为'module’的链接文件，链接到module文件夹 driver_name = make_driver_name(drv); //生成driver_name,给module用，见4-4-1分析 if (driver_name) { module_create_drivers_dir(mk); //在具体的module文件夹下创建driver目录 no_warn = sysfs_create_link(mk->drivers_dir, &drv->p->kobj, //在上面创建的driver目录下，生成一个名为driver_name指定的链接文件，链接到驱动的文件夹 make_driver_name(); kfree(driver_name); } } 4-4-1，make_driver_name() static char *make_driver_name(struct device_driver *drv) { char *driver_name; driver_name = kmalloc(strlen(drv->name) + strlen(drv->bus->name) + 2, GFP_KERNEL); //申请这么大内存 if (!driver_name) return NULL; sprintf(driver_name, "%s:%s", drv->bus->name, drv->name); //将bus的名字和驱动的名字组成一块，中间加一个冒号 return driver_name; } 这个函数的功能就是生成一个名字，这个有bus和驱动的名字组成 4-5， 在drivers/base/bus.c中driver_attr_uevent，driver_attr_unbind，driver_attr_bind这几个属性的定义如下： static DRIVER_ATTR(uevent, S_IWUSR, NULL, driver_uevent_store); static DRIVER_ATTR(unbind, S_IWUSR, NULL, driver_unbind); static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind); 在include/linux/device.h中DRIVER_ATTR宏的定义如下： #define DRIVER_ATTR(_name, _mode, _show, _store) / struct driver_attribute driver_attr_##_name = / __ATTR(_name, _mode, _show, _store) 由定义可知，这三个属性文件的_show函数都为null，也就是都不具体读的功能。 4-5-1，driver_attr_uevent，_store为driver_uevent_store： static ssize_t driver_uevent_store(struct device_driver *drv, const char *buf, size_t count) { enum kobject_action action; if (kobject_action_type(buf, count, &action) == 0) //kobject_action_type就是将buf转换成action kobject_uevent(&drv->p->kobj, action); //产生一个action的uevent事件，一般通过netlink机制与用户空间通信,见4-5-1-1分析 return count; } 也就是说对drvier目录下的uevent属性文件进行写操作时将会产生一个用户指定的事件。 4-5-1-1，kobject_uevent() int kobject_uevent(struct kobject *kobj, enum kobject_action action) { return kobject_uevent_env(kobj, action, NULL); } 转而看kobject_uevent_env(): int kobject_uevent_env(struct kobject *kobj, enum kobject_action action, char *envp_ext[]) { struct kobj_uevent_env *env; const char *action_string = kobject_actions[action]; //通过数组下标找到对应的字符串 const char *devpath = NULL; const char *subsystem; struct kobject *top_kobj; struct kset *kset; struct kset_uevent_ops *uevent_ops; u64 seq; int i = 0; int retval = 0; pr_debug("kobject: '%s' (%p): %s\n", kobject_name(kobj), kobj, __func__); /* search the kset we belong to */ top_kobj = kobj; while (!top_kobj->kset && top_kobj->parent) top_kobj = top_kobj->parent; //通过不断往前找父kobj，从而得到top kobj if (!top_kobj->kset) { //top kobj不能为null pr_debug("kobject: '%s' (%p): %s: attempted to send uevent " "without kset!\n", kobject_name(kobj), kobj, __func__); return -EINVAL; } kset = top_kobj->kset; //找到以后赋值 uevent_ops = kset->uevent_ops; /* skip the event, if uevent_suppress is set*/ if (kobj->uevent_suppress) { pr_debug("kobject: '%s' (%p): %s: uevent_suppress " "caused the event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* skip the event, if the filter returns zero. */ if (uevent_ops && uevent_ops->filter) //判断是否要进行的event if (!uevent_ops->filter(kset, kobj)) { pr_debug("kobject: '%s' (%p): %s: filter function " "caused the event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* originating subsystem */ if (uevent_ops && uevent_ops->name) //得到subsystem subsystem = uevent_ops->name(kset, kobj); else subsystem = kobject_name(&kset->kobj); if (!subsystem) { pr_debug("kobject: '%s' (%p): %s: unset subsystem caused the " "event to drop!\n", kobject_name(kobj), kobj, __func__); return 0; } /* environment buffer */ env = kzalloc(sizeof(struct kobj_uevent_env), GFP_KERNEL); //申请环境变量buffer if (!env) return -ENOMEM; /* complete object path */ devpath = kobject_get_path(kobj, GFP_KERNEL); //得到该kobj的完整路径 if (!devpath) { retval = -ENOENT; goto exit; } /* default keys */ retval = add_uevent_var(env, "ACTION=%s", action_string); //将action的字符串添加到buffer中 if (retval) goto exit; retval = add_uevent_var(env, "DEVPATH=%s", devpath); //同上 if (retval) goto exit; retval = add_uevent_var(env, "SUBSYSTEM=%s", subsystem); //同上 if (retval) goto exit; /* keys passed in from the caller */ if (envp_ext) { //如果不为空,则也添加到buffer中 for (i = 0; envp_ext[i]; i++) { retval = add_uevent_var(env, "%s", envp_ext[i]); if (retval) goto exit; } } /* let the kset specific function add its stuff */ if (uevent_ops && uevent_ops->uevent) { //该集合的特定要加的东西到buffer中 retval = uevent_ops->uevent(kset, kobj, env); if (retval) { pr_debug("kobject: '%s' (%p): %s: uevent() returned " "%d\n", kobject_name(kobj), kobj, __func__, retval); goto exit; } } /* * Mark "add" and "remove" events in the object to ensure proper * events to userspace during automatic cleanup. If the object did * send an "add" event, "remove" will automatically generated by * the core, if not already done by the caller. */ if (action == KOBJ_ADD) //标记一下 kobj->state_add_uevent_sent = 1; else if (action == KOBJ_REMOVE) kobj->state_remove_uevent_sent = 1; /* we will send an event, so request a new sequence number */ spin_lock(&sequence_lock); seq = ++uevent_seqnum; spin_unlock(&sequence_lock); retval = add_uevent_var(env, "SEQNUM=%llu", (unsigned long long)seq); //添加新的序列号到buffer中 if (retval) goto exit; #if defined(CONFIG_NET) //一般情况都定义的,通过netlink机制实现hotplug的 /* send netlink message */ if (uevent_sock) { struct sk_buff *skb; size_t len; /* allocate message with the maximum possible size */ len = strlen(action_string) + strlen(devpath) + 2; skb = alloc_skb(len + env->buflen, GFP_KERNEL); //申请skb buffer if (skb) { char *scratch; /* add header */ scratch = skb_put(skb, len); //将scratch指向skb的tail,且后面有len大小的长度，相当与skb的位置指针，对它的赋值，实质是对skb buffer的赋值 sprintf(scratch, "%s@%s", action_string, devpath); //将action和路径添加到scratch /* copy keys to our continuous event payload buffer */ for (i = 0; i < env->envp_idx; i++) { len = strlen(env->envp[i]) + 1; scratch = skb_put(skb, len); strcpy(scratch, env->envp[i]);//将envp[]添加到scratch } NETLINK_CB(skb).dst_group = 1; //目标组地址 retval = netlink_broadcast(uevent_sock, skb, 0, 1, //发送广播消息 GFP_KERNEL); /* ENOBUFS should be handled in userspace */ if (retval == -ENOBUFS) retval = 0; } else retval = -ENOMEM; } #endif /* call uevent_helper, usually only enabled during early boot */ if (uevent_helper[0]) { //从定义看该数组值为"/sbin/hotplug"，现在一般udev系统已经没有这个执行文件了，所以下面一般也不会执行，所以这里不做分析 char *argv [3]; argv [0] = uevent_helper; argv [1] = (char *)subsystem; argv [2] = NULL; retval = add_uevent_var(env, "HOME=/"); if (retval) goto exit; retval = add_uevent_var(env, "PATH=/sbin:/bin:/usr/sbin:/usr/bin"); if (retval) goto exit; retval = call_usermodehelper(argv[0], argv, env->envp, UMH_WAIT_EXEC); } exit: kfree(devpath); kfree(env); return retval; } 4-5-2，driver_attr_bind属性对应的写函数如下： static ssize_t driver_bind(struct device_driver *drv, const char *buf, size_t count) { struct bus_type *bus = bus_get(drv->bus); struct device *dev; int err = -ENODEV; dev = bus_find_device_by_name(bus, NULL, buf); //在bus上寻找buf指定的device if (dev && dev->driver == NULL) { if (dev->parent) /* Needed for USB */ down(&dev->parent->sem); down(&dev->sem); err = driver_probe_device(drv, dev); //在4-2-1-1-2中我们已经分析了driver_probe_device()，它的作用就是将driver和dev绑定起来，生成一些互相连接文件 up(&dev->sem); if (dev->parent) up(&dev->parent->sem); if (err > 0) { /* success */ err = count; } else if (err == 0) { /* driver didn't accept device */ err = -ENODEV; } } put_device(dev); bus_put(bus); return err; } 从该函数可以看出，对bind写入一个device的名字，将会绑定设备和驱动。 4-5-3，driver_attr_unbind，对应的写函数如下： static ssize_t driver_unbind(struct device_driver *drv, const char *buf, size_t count) { struct bus_type *bus = bus_get(drv->bus); struct device *dev; int err = -ENODEV; dev = bus_find_device_by_name(bus, NULL, buf); //同样在bus上寻找buf指定的device if (dev && dev->driver == drv) { if (dev->parent) /* Needed for USB */ down(&dev->parent->sem); device_release_driver(dev); //断开设备和驱动 if (dev->parent) up(&dev->parent->sem); err = count; } put_device(dev); bus_put(bus); return err; } 从该函数可以看出，对unbind写入一个device的名字，将会断开设备和驱动。 至此，我们已经详细地分析了driver_register(),下面我们将开始分析device_register(). |
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