在linux驱动模型中，为了便于管理各种设备，我们把不同设备分别挂在他们对应的总线上，设备对应的驱动程序也在总线上找，这样就提出了deivce-bus-driver的模型，硬件上有许多设备总线，那么我们就在设备模型上抽象出bus概念，相应的device就代表设备，driver表示驱动，在代码中它们对应的结构体下面介绍，对于实际的设备及总线，这些结构体就可以嵌入到实际总线上。

1. bus

了解bus，就要先介绍下bus的结构体，一条总线定义完后要注册到系统中，第二节介绍注册函数，最后再介绍下其他一些相关API

1.1 struct bus_type

struct bus_type {const char      *name;--------------------------------------------总线名字const char      *dev_name;struct device       *dev_root;struct device_attribute *dev_attrs; /* use dev_groups instead */const struct attribute_group **bus_groups;const struct attribute_group **dev_groups;const struct attribute_group **drv_groups;int (*match)(struct device *dev, struct device_driver *drv);-------匹配函数(用于匹配device&driver)int (*uevent)(struct device *dev, struct kobj_uevent_env *env);int (*probe)(struct device *dev);----------------------------------用于初始化驱动int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*online)(struct device *dev);int (*offline)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);-----------PM相关int (*resume)(struct device *dev);--------------------------------PM相关const struct dev_pm_ops *pm;--------------------------------------PM相关const struct iommu_ops *iommu_ops;struct subsys_private *p;struct lock_class_key lock_key;
};

1.2 注册总线

int bus_register(struct bus_type *bus)
{int retval;struct subsys_private *priv;struct lock_class_key *key = &bus->lock_key;priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);if (!priv)return -ENOMEM;priv->bus = bus;bus->p = priv;BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);if (retval)goto out;priv->subsys.kobj.kset = bus_kset;priv->subsys.kobj.ktype = &bus_ktype;priv->drivers_autoprobe = 1;retval = kset_register(&priv->subsys);--------------------在/sys/bus目录下创建当前总线目录if (retval)goto out;retval = bus_create_file(bus, &bus_attr_uevent);----------在当前总线目录下创建文件ueventif (retval)goto bus_uevent_fail;priv->devices_kset = kset_create_and_add("devices", NULL,&priv->subsys.kobj);-----------------在当前总线目录下创建devices目录if (!priv->devices_kset) {retval = -ENOMEM;goto bus_devices_fail;}priv->drivers_kset = kset_create_and_add("drivers", NULL,&priv->subsys.kobj);----------------在当前总线目录下创建drivers目录if (!priv->drivers_kset) {retval = -ENOMEM;goto bus_drivers_fail;}INIT_LIST_HEAD(&priv->interfaces);__mutex_init(&priv->mutex, "subsys mutex", key);klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);klist_init(&priv->klist_drivers, NULL, NULL);retval = add_probe_files(bus);-------------------------在当前总线目录下创建probe相关文件if (retval)goto bus_probe_files_fail;retval = bus_add_groups(bus, bus->bus_groups);if (retval)goto bus_groups_fail;pr_debug("bus: '%s': registered\n", bus->name);return 0;。。。。。。
}

1.3 其他API

总线卸载函数

extern void bus_unregister(struct bus_type *bus);

2. device

先介绍devices结构体，在介绍注册函数

2.1 struct device

struct device {struct device       *parent;-------------------------父设备struct device_private   *p;struct kobject kobj;--------------------------------嵌入的kobjectconst char      *init_name; /* initial name of the device */const struct device_type *type;---------------------所属的device类型struct mutex        mutex;  /* mutex to synchronize calls to* its driver.*/struct bus_type *bus;       /* type of bus device is on */---所属的busstruct device_driver *driver;   /* which driver has allocated thisdevice */---------------------------------对应的驱动drivervoid        *platform_data; /* Platform specific data, devicecore doesn't touch it */------------------私有platform数据void        *driver_data;   /* Driver data, set and get withdev_set/get_drvdata */--------------------私有driver数据struct dev_pm_info  power;-----------------------------------PM相关struct dev_pm_domain    *pm_domain;--------------------------PM相关#ifdef CONFIG_PINCTRLstruct dev_pin_info *pins;
#endif#ifdef CONFIG_NUMAint     numa_node;  /* NUMA node this device is close to */
#endifu64     *dma_mask;  /* dma mask (if dma'able device) */u64     coherent_dma_mask;/* Like dma_mask, but foralloc_coherent mappings asnot all hardware supports64 bit addresses for consistentallocations such descriptors. */unsigned long   dma_pfn_offset;struct device_dma_parameters *dma_parms;struct list_head    dma_pools;  /* dma pools (if dma'ble) */struct dma_coherent_mem *dma_mem; /* internal for coherent memoverride */
#ifdef CONFIG_DMA_CMAstruct cma *cma_area;       /* contiguous memory area for dmaallocations */
#endif/* arch specific additions */struct dev_archdata archdata;struct device_node  *of_node; /* associated device tree node */------设备树相关struct fwnode_handle    *fwnode; /* firmware device node */dev_t           devt;   /* dev_t, creates the sysfs "dev" */u32         id; /* device instance */spinlock_t      devres_lock;struct list_head    devres_head;-----------------------------------devres相关struct klist_node   knode_class;struct class        *class;----------------------------------------所属的classconst struct attribute_group **groups;  /* optional groups */void    (*release)(struct device *dev);struct iommu_group  *iommu_group;bool            offline_disabled:1;bool            offline:1;
};

2.2 设备注册函数

device的注册函数device_register分两步，先初始化device_initialize，主要是初始化所属的kset为/sys/devices目录，及其他（如PM相关），然后再注册，函数为device_add

int device_add(struct device *dev)
{struct device *parent = NULL;struct kobject *kobj;struct class_interface *class_intf;int error = -EINVAL;dev = get_device(dev);if (!dev)goto done;if (!dev->p) {error = device_private_init(dev);if (error)goto done;}/** 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);------------------有初始name就设置dev->init_name = NULL;}/* subsystems can specify simple device enumeration */if (!dev_name(dev) && dev->bus && dev->bus->dev_name)dev_set_name(dev, "%s%u", dev->bus->dev_name, dev->id);---没有初始name就设置默认的if (!dev_name(dev)) {error = -EINVAL;goto name_error;}pr_debug("device: '%s': %s\n", dev_name(dev), __func__);parent = get_device(dev->parent);kobj = get_device_parent(dev, parent);if (kobj)dev->kobj.parent = kobj;/* use parent numa_node */if (parent && (dev_to_node(dev) == NUMA_NO_NODE))set_dev_node(dev, dev_to_node(parent));/* 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);---在/sys/devices目录下创建当前设备目录if (error)goto Error;/* notify platform of device entry */if (platform_notify)platform_notify(dev);error = device_create_file(dev, &dev_attr_uevent);--------在当前设备目录下创建文件ueventif (error)goto attrError;error = device_add_class_symlinks(dev);-------------------创建链接文件if (error)goto SymlinkError;error = device_add_attrs(dev);----------------------------创建其他文件，如在class目录下if (error)goto AttrsError;error = bus_add_device(dev);------------------------------device加入到bus-device的链表中if (error)goto BusError;error = dpm_sysfs_add(dev);if (error)goto DPMError;device_pm_add(dev);if (MAJOR(dev->devt)) {error = device_create_file(dev, &dev_attr_dev);if (error)goto DevAttrError;error = device_create_sys_dev_entry(dev);if (error)goto SysEntryError;devtmpfs_create_node(dev);}/* Notify clients of device addition.  This call must come* after dpm_sysfs_add() and before kobject_uevent().*/if (dev->bus)blocking_notifier_call_chain(&dev->bus->p->bus_notifier,BUS_NOTIFY_ADD_DEVICE, dev);kobject_uevent(&dev->kobj, KOBJ_ADD);bus_probe_device(dev);--------__device_attach-------调用此函数来和driver进行匹配if (parent)-----------------------------------------加入到父设备链表中klist_add_tail(&dev->p->knode_parent,&parent->p->klist_children);if (dev->class) {-----------------------------------和class相关的操作mutex_lock(&dev->class->p->mutex);/* tie the class to the device */klist_add_tail(&dev->knode_class,&dev->class->p->klist_devices);/* notify any interfaces that the device is here */list_for_each_entry(class_intf,&dev->class->p->interfaces, node)if (class_intf->add_dev)class_intf->add_dev(dev, class_intf);mutex_unlock(&dev->class->p->mutex);}
。。。。。。
}

具体device如何匹配到对应的driver在函数__device_attach中进行，加入开始device没有driver，那么会在bus中找到对应的driver，看下函数__device_attach

static int __device_attach(struct device *dev, bool allow_async)
{int ret = 0;device_lock(dev);if (dev->driver) {if (device_is_bound(dev)) {ret = 1;goto out_unlock;}ret = device_bind_driver(dev);---------如果已经有driver，那么就绑定到device并进行probeif (ret == 0)ret = 1;else {dev->driver = NULL;ret = 0;}} else {struct device_attach_data data = {.dev = dev,.check_async = allow_async,.want_async = false,};if (dev->parent)pm_runtime_get_sync(dev->parent);ret = bus_for_each_drv(dev->bus, NULL, &data,__device_attach_driver);----如果没有driver，就遍历总线上的driver，直到找到并进行probeif (!ret && allow_async && data.have_async) {/** If we could not find appropriate driver* synchronously and we are allowed to do* async probes and there are drivers that* want to probe asynchronously, we'll* try them.*/dev_dbg(dev, "scheduling asynchronous probe\n");get_device(dev);async_schedule(__device_attach_async_helper, dev);} else {pm_request_idle(dev);}if (dev->parent)pm_runtime_put(dev->parent);}
out_unlock:device_unlock(dev);return ret;
}

2.3 其他API

device卸载函数

extern void device_unregister(struct device *dev);

3. driver

先介绍driver的结构体，再介绍注册函数

3.1 struct device_driver

struct device_driver {const char      *name;-----------------------------driver名字struct bus_type     *bus;--------------------------所属总线struct module       *owner;const char      *mod_name;  /* used for built-in modules */bool suppress_bind_attrs;   /* disables bind/unbind via sysfs */enum probe_type probe_type;const struct of_device_id   *of_match_table;const struct acpi_device_id *acpi_match_table;int (*probe) (struct device *dev);----------------探测初始化函数int (*remove) (struct device *dev);---------------删除函数void (*shutdown) (struct device *dev);int (*suspend) (struct device *dev, pm_message_t state);---PM相关int (*resume) (struct device *dev);------------------------PM相关const struct attribute_group **groups;const struct dev_pm_ops *pm;-------------------------------PM相关struct driver_private *p;
};

3.2 注册函数

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);if (other) {printk(KERN_ERR "Error: Driver '%s' is already registered, ""aborting...\n", drv->name);return -EBUSY;}ret = bus_add_driver(drv);--------------------主要在这里进行注册if (ret)return ret;ret = driver_add_groups(drv, drv->groups);if (ret) {bus_remove_driver(drv);return ret;}kobject_uevent(&drv->p->kobj, KOBJ_ADD);return ret;
}

看下函数bus_add_driver

int bus_add_driver(struct device_driver *drv)
{struct bus_type *bus;struct driver_private *priv;int error = 0;bus = bus_get(drv->bus);-----------------------得到所属的总线if (!bus)return -EINVAL;pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);priv = kzalloc(sizeof(*priv), GFP_KERNEL);if (!priv) {error = -ENOMEM;goto out_put_bus;}klist_init(&priv->klist_devices, NULL, NULL);priv->driver = drv;drv->p = priv;priv->kobj.kset = bus->p->drivers_kset;-------设置所属总线的driverserror = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,"%s", drv->name);------------在所属总线的drivers目录下创建本驱动目录if (error)goto out_unregister;klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);---把本驱动加入到总线驱动链表中if (drv->bus->p->drivers_autoprobe) {if (driver_allows_async_probing(drv)) {pr_debug("bus: '%s': probing driver %s asynchronously\n",drv->bus->name, drv->name);async_schedule(driver_attach_async, drv);} else {error = driver_attach(drv);if (error)goto out_unregister;}}------------------__driver_attach--------------调用此函数来进行探测初始化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_groups(drv, bus->drv_groups);if (error) {/* How the hell do we get out of this pickle? Give up */printk(KERN_ERR "%s: driver_create_groups(%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);}}return 0;
。。。。。。。。
}

那么驱动是如何匹配到对应的device的，继续探索函数__driver_attach

（drivers/base/dd.c）

static int __driver_attach(struct device *dev, void *data)
{struct device_driver *drv = data;int ret;/** 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.*/ret = driver_match_device(drv, dev);--------调用总线的match函数来进行匹配if (ret == 0) {/* no match */
        return 0;} else if (ret == -EPROBE_DEFER) {dev_dbg(dev, "Device match requests probe deferral\n");driver_deferred_probe_add(dev);} else if (ret < 0) {dev_dbg(dev, "Bus failed to match device: %d", ret);
        return ret;} /* ret > 0 means positive match */if (dev->parent)    /* Needed for USB */device_lock(dev->parent);device_lock(dev);if (!dev->driver)driver_probe_device(drv, dev);------没有driver就设置此driver为device的driver，然后调用驱动probe初始化device_unlock(dev);if (dev->parent)device_unlock(dev->parent);
return 0;
}

3.3 其他API

卸载函数

extern void driver_unregister(struct device_driver *drv);

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