driver_register函数深入理解
/**
* 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
va_start(args, fmt); //动态可变参数的使用
retval = kobject_add_varg(kobj, parent, fmt, args);
va_end(args);
return retval;
}
4-1-1，kobject_init()
void kobject_init(struct kobject *kobj, struct kobj_type *ktype)
{
...
kobject_init_internal(kobj);
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4-2-1
}
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bus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) : "",
kobj->kset ? kobject_name(&kobj->kset->kobj) : "");
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4-2-1-1-1
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 *))
{
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);
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().