linux内核学习（23）设备模型之第二层driver_register

终于说到最后一个注册了，今天也是年末了，可是我依然战斗在一线的感觉！说完这个，我也得放松一会儿。学习内核也接近大半个月了，收获颇多，不过还有太多东西需要我在继续努力了，虽然博客的流量不是很理想，表明关注我博客的网友不是很多，但是我相信，就会在不久，linux成为千家万户都在关注的对象时，我博客将成为初学者很好的入门资料，这也是我写这些文章的一个出发点，希望以后在来回味自己走过linux的路程时有所感慨！

来自：drivers/base/driver.c：
int driver_register(struct device_driver *drv)
{
int ret;
struct device_driver *other;

BUG_ON(!drv->bus->p);

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);

other = driver_find(drv->name, drv->bus);
//比较好理解的函数，也就是在总线中找到和该驱动同名的驱动
//说白了，就是看看这个驱动之前注册过没
if (other) {
put_driver(other); //如果注册过，那么我们将不再注册，注意减少驱动引用，因为在driver_find中增加过
printk(KERN_ERR "Error: Driver '%s' is already registered, "
"aborting.../n", drv->name);
return -EBUSY;
}

ret = bus_add_driver(drv); //如果没有注册过，那么我们将该驱动加入总线中
if (ret)
return ret;
ret = driver_add_groups(drv, drv->groups);
if (ret)
bus_remove_driver(drv);
return ret;
}

struct device_driver *driver_find(const char *name, struct bus_type *bus)
{
struct kobject *k = kset_find_obj(bus->p->drivers_kset, name);
//这个函数顾名思义，就是在总线集合中找到名称为name的kobject对象，其实就是驱动名称了
struct driver_private *priv;

if (k) { //如果找到了
priv = to_driver(k);
return priv->driver; //返回驱动指针
}
return NULL;
}

int bus_add_driver(struct device_driver *drv)
{
struct bus_type *bus;
struct driver_private *priv;
int error = 0;

bus = bus_get(drv->bus);
if (!bus)
return -EINVAL;

pr_debug("bus: '%s': add driver %s/n", bus->name, drv->name);

priv = kzalloc(sizeof(*priv), GFP_KERNEL); //为驱动私有成员申请内存且清0
if (!priv) {
error = -ENOMEM;
goto out_put_bus;
}
klist_init(&priv->klist_devices, NULL, NULL); //初始化驱动所支持的设备链表
priv->driver = drv;
drv->p = priv;
priv->kobj.kset = bus->p->drivers_kset; //设置驱动kobject所属集合，显然这里就是对于总线的驱动集合
error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
"%s", drv->name); //初始化并添加驱动kobject对象到总线驱动中
if (error)
goto out_unregister;

if (drv->bus->p->drivers_autoprobe) { //还记得我说过这个变量，
error = driver_attach(drv); //如果需要自动的去匹配，那么调用驱动匹配函数
if (error)
goto out_unregister;
}
klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers); //将驱动节点加入到总线链表中
module_add_driver(drv->owner, drv);

error = driver_create_file(drv, &driver_attr_uevent);
if (error) {
printk(KERN_ERR "%s: uevent attr (%s) failed/n",
__func__, drv->name);
}
error = driver_add_attrs(bus, drv);
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);
}

if (!drv->suppress_bind_attrs) {
error = add_bind_files(drv);
if (error) {
/* Ditto */
printk(KERN_ERR "%s: add_bind_files(%s) failed/n",
__func__, drv->name);
}
}

kobject_uevent(&priv->kobj, KOBJ_ADD);
return 0;

out_unregister:
kobject_put(&priv->kobj);
kfree(drv->p);
drv->p = NULL;
out_put_bus:
bus_put(bus);
return error;
}

来自base/dd.c：
int driver_attach(struct device_driver *drv)
{
return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}

来自base/bus.c：
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));
//初始化i结构体，我们可以进去看看
while ((dev = next_device(&i)) && !error) //在总线的设备链表中遍历链表
error = fn(dev, data); //然后将设备和驱动进行匹配，这个fn=__driver_attch
klist_iter_exit(&i); //清除i结构体
return error;
}

struct klist_iter {
struct klist *i_klist; //所属链表
struct klist_node *i_cur; //链表中的节点
};

void klist_iter_init_node(struct klist *k, struct klist_iter *i,
struct klist_node *n)
{
i->i_klist = k;
i->i_cur = n; //这里的n为NULL
if (n)
kref_get(&n->n_ref);
}

static struct device *next_device(struct klist_iter *i)
{
struct klist_node *n = klist_next(i); //以i->i_cur节点为起点，得到链表i->i_klist的下一个节点
struct device *dev = NULL;
struct device_private *dev_prv;

if (n) { //如果有，返回该设备
dev_prv = to_device_private_bus(n);
dev = dev_prv->device;
}
return dev;
}

struct klist_node *klist_next(struct klist_iter *i)
{
void (*put)(struct klist_node *) = i->i_klist->put;
struct klist_node *last = i->i_cur;
struct klist_node *next;

spin_lock(&i->i_klist->k_lock);

if (last) { //这里的last为空
next = to_klist_node(last->n_node.next);
if (!klist_dec_and_del(last))
put = NULL;
} else
next = to_klist_node(i->i_klist->k_list.next); //得到链表的第一个节点

i->i_cur = NULL;
while (next != to_klist_node(&i->i_klist->k_list)) { //遍历链表，如果没有到头
if (likely(!knode_dead(next))) { //如果发现节点next为有效节点
kref_get(&next->n_ref); //增加节点引用
i->i_cur = next; //将i结构的起始节点设为next
break;
}
next = to_klist_node(next->n_node.next); //继续遍历链表中下一个节点
}

spin_unlock(&i->i_klist->k_lock);

if (put && last)
put(last);
return i->i_cur;
}

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)) //将驱动和设备匹配，如果成功返回0
return 0;

//总线去匹配没有成功不要紧，因为，它只是一个很低级的匹配函数，我们还有更高级的
if (dev->parent) /* Needed for USB */
device_lock(dev->parent);
device_lock(dev);
if (!dev->driver)
driver_probe_device(drv, dev); //驱动去匹配设备的高级匹配函数
device_unlock(dev);
if (dev->parent)
device_unlock(dev->parent);

return 0;
}

static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;
//这里就要用到总线的match函数了，所有的匹配都是通过它来的
}

int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;

if (!device_is_registered(dev)) //设备是否注册过，显然这里肯定注册过
return -ENODEV;

pr_debug("bus: '%s': %s: matched device %s with driver %s/n",
drv->bus->name, __func__, dev_name(dev), drv->name);

pm_runtime_get_noresume(dev); //pm_xxx电源管理类
pm_runtime_barrier(dev);
ret = really_probe(dev, drv); //真正执行的寒酸
pm_runtime_put_sync(dev);

return ret;
}

static int really_probe(struct device *dev, struct device_driver *drv)
{
int ret = 0;

atomic_inc(&probe_count);
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;
if (driver_sysfs_add(dev)) {
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed/n",
__func__, dev_name(dev));
goto probe_failed;
}

if (dev->bus->probe) { //如果总线的probe函数存在就用总线的
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) { //总线不存在，则看驱动的probe寒酸
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}

driver_bound(dev); //将设备绑定到驱动上
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;
}

static void driver_bound(struct device *dev)
{
if (klist_node_attached(&dev->p->knode_driver)) { //如果设备已经绑定到了一个驱动，则返回
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);

klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); //将设备节点加入到该设备对应的驱动链表中

if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
BUS_NOTIFY_BOUND_DRIVER, dev);
}

总体来说，驱动的注册比较复杂，但是我们可以简单概况一下。
1、在总线上找找该驱动有没有被注册过
2、若没有注册过，则将驱动加入到总线驱动集合中
3、在总线上找能匹配驱动的设备
1、将总线上每个设备进行匹配
2、首先用总线的match 函数进行低级匹配
3、然后在用总线的probe函数进行高级匹配，若失败，则用驱动上的probe寒酸进行高级匹配
4、如果匹配成功，则将设备绑定到驱动链表中
4、如果匹配成功，则将驱动加入到总线的驱动链表中

好不容易啊，我们终于将3大注册函数说完，很兴奋，下一步做什么呢？其实我也不知道，继续探索吧... ....