目录
一. 总线(bus)、设备(device)、驱动(driver)模型
内核版本：3.18.20
博客：https://blog.csdn.net/yj4231/article/details/7799245
https://blog.csdn.net/adc0809608/article/details/7254684
一. 总线(bus)、设备(device)、驱动(driver)模型
1.1 简介
大多数情况下， Linux内核中的设备模型代码会作为“幕后黑手” 处理好这些关系，内核中的总线和其他内核子系统会完成与设备模型的交互，这使得驱动工程师几乎不需要关心设备模型，只需要按照每个框架的要求，“填鸭式”地填充xxx_driver里面的各种回调函数（xxx是总线的名称）在 Linux 内核中，分别使用 bus_type、 device_driver 和 device 来描述总线、驱动和设备。
1.2工作流程
device_driver和device分别表示驱动和设备，而这两者都必须依附于一种总线，因此都包含struct bus_type指针。在linux内核中，设备和驱动是分开注册的，注册1个设备的时候，并不需要驱动已经存在，而1个驱动被注册的时候，也不需要对应的设备已经被注册。设备和驱动各自涌向内核，而每个设备和驱动涌向内核的时候，都会去寻找自己的另一半，而正是bus_type的match()成员函数将两者捆绑在一起。
简单地说，设备和驱动就是红尘中漂浮的男女，而bus_type的match()则是牵引红线的月老，它可以识别什么设备与什么驱动是可配对的。一旦配对成功，xxx_driver的probe()就被执行。(xxx是总线名，如platform、pci、i2c、spi、usb等)
注：总线、驱动和设备最终都会落实为sysfs中的一个目录，因为进一步追踪代码会发现，他们实际上都可以认为是kobject的派生类，kobject可看作是所有总线、设备和驱动的抽象基类，一个kobject对应sysfs中的一个目录。
二. bus
2.1 简介
总线是处理器与一个设备或者多个设备之间的通道。在设备模型中，所有的设备都挂载在某一个总线上。
内核表示：
/*路径：include/linux/device.h*/
/**
* struct bus_type - The bus type of the device
*
* @name: The name of the bus.
* @dev_name: Used for subsystems to enumerate devices like ("foo%u", dev->id).
* @dev_root: Default device to use as the parent.
* @dev_attrs: Default attributes of the devices on the bus.
* @bus_groups: Default attributes of the bus.
* @dev_groups: Default attributes of the devices on the bus.
* @drv_groups: Default attributes of the device drivers on the bus.
* @match: Called, perhaps multiple times, whenever a new device or driver
* is added for this bus. It should return a nonzero value if the
* given device can be handled by the given driver.
* @uevent: Called when a device is added, removed, or a few other things
* that generate uevents to add the environment variables.
* @probe: Called when a new device or driver add to this bus, and callback
* the specific driver's probe to initial the matched device.
* @remove: Called when a device removed from this bus.
* @shutdown: Called at shut-down time to quiesce the device.
*
* @online: Called to put the device back online (after offlining it).
* @offline: Called to put the device offline for hot-removal. May fail.
*
* @suspend: Called when a device on this bus wants to go to sleep mode.
* @resume: Called to bring a device on this bus out of sleep mode.
* @pm: Power management operations of this bus, callback the specific
* device driver's pm-ops.
* @iommu_ops: IOMMU specific operations for this bus, used to attach IOMMU
* driver implementations to a bus and allow the driver to do
* bus-specific setup
* @p: The private data of the driver core, only the driver core can
* touch this.
* @lock_key: Lock class key for use by the lock validator
*
* A bus is a channel between the processor and one or more devices. For the
* purposes of the device model, all devices are connected via a bus, even if
* it is an internal, virtual, "platform" bus. Buses can plug into each other.
* A USB controller is usually a PCI device, for example. The device model
* represents the actual connections between buses and the devices they control.
* A bus is represented by the bus_type structure. It contains the name, the
* default attributes, the bus' methods, PM operations, and the driver core's
* private data.
*/
struct bus_type {
const char *name;
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);
int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
int (*probe)(struct device *dev);
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);
int (*resume)(struct device *dev);
const struct dev_pm_ops *pm;
const struct iommu_ops *iommu_ops;
struct subsys_private *p;
struct lock_class_key lock_key;
};
/**
* struct subsys_private - structure to hold the private to the driver core portions of the bus_type/class structure.
*
* @subsys - the struct kset that defines this subsystem
* @devices_kset - the subsystem's 'devices' directory
* @interfaces - list of subsystem interfaces associated
* @mutex - protect the devices, and interfaces lists.
*
* @drivers_kset - the list of drivers associated
* @klist_devices - the klist to iterate over the @devices_kset
* @klist_drivers - the klist to iterate over the @drivers_kset
* @bus_notifier - the bus notifier list for anything that cares about things
* on this bus.
* @bus - pointer back to the struct bus_type that this structure is associated
* with.
*
* @glue_dirs - "glue" directory to put in-between the parent device to
* avoid namespace conflicts
* @class - pointer back to the struct class that this structure is associated
* with.
*
* This structure is the one that is the actual kobject allowing struct
* bus_type/class to be statically allocated safely. Nothing outside of the
* driver core should ever touch these fields.
*/
struct subsys_private {
struct kset subsys;
struct kset *devices_kset;
struct list_head interfaces;
struct mutex mutex;
struct kset *drivers_kset;
struct klist klist_devices;
struct klist klist_drivers;
struct blocking_notifier_head bus_notifier;
unsigned int drivers_autoprobe:1;
struct bus_type *bus;
struct kset glue_dirs;
struct class *class;
};
/*可得：
- 每个bus_type都包含一个kset对象subsys，该kset在/sys/bus/目录下有着对应的一个目录，目录名即为字段name。
- drivers_kset和devices_kset对应着两个目录，该两个目录下将包含该总线上的设备和相应的驱动程序。
- 总线上的设备和驱动将分别保存在两个链表中：klist_devices和klist_drivers。
*/
2.2实例--platform总线
2.2.1 platform总线建立流程
platform总线的注册是由platform_bus_init函数完成的。该函数在内核启动阶段被调用，我们来简单看下调用过程：
- 调用流程：
start_kernel() /*路径：/init/main.c*/
rest_init()
kernel_thread(kernel_init, NULL, CLONE_FS) /*即调用kernel_init() */
kernel_init_freeable()
do_basic_setup()
driver_init() /*路径：drivers/base/init.c*/
platform_bus_init() /*路径：drivers/base/platform.c*/
注：kernel_init()是在rest_init函数中创建内核线程来执行的。
2.2.2 相关函数讲解
/*1.platform_bus_init()*/
struct bus_type platform_bus_type = {
.name = "platform",
.dev_groups = platform_dev_groups,
.match = platform_match,
.uevent = platform_uevent,
.pm = &platform_dev_pm_ops,
};
EXPORT_SYMBOL_GPL(platform_bus_type);
int __init platform_bus_init(void)
{
int error;
early_platform_cleanup();
error = device_register(&platform_bus);
if (error)
return error;
error = bus_register(&platform_bus_type);
if (error)
device_unregister(&platform_bus);
return error;
}
/*2.bus_register()*/
/**
* bus_register - register a driver-core subsystem
* @bus: bus to register
*
* Once we have that, we register the bus with the kobject
* infrastructure, then register the children subsystems it has:
* the devices and drivers that belong to the subsystem.
*/
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;
/*相互保存*/
priv->bus = bus;
bus->p = priv;
BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);
/*设置bus set的名字，即kobject->name*/
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;
/*注册kset，即在sysfs的bus目录下，建立子目录xxx （xxx:为bus->name）*/
retval = kset_register(&priv->subsys);
if (retval)
goto out;
/*创建属性文件，即bus/xxx/文件uevent*/
retval = bus_create_file(bus, &bus_attr_uevent);
if (retval)
goto bus_uevent_fail;
/*创建devices kset，在bus/xxx/目录devices*/
priv->devices_kset = kset_create_and_add("devices", NULL,
&priv->subsys.kobj);
if (!priv->devices_kset) {
retval = -ENOMEM;
goto bus_devices_fail;
}
/*创建drivers kset，在bus/xxx/目录drivers*/
priv->drivers_kset = kset_create_and_add("drivers", NULL,
&priv->subsys.kobj);
if (!priv->drivers_kset) {
retval = -ENOMEM;
goto bus_drivers_fail;
}
INIT_LIST_HEAD(&priv->interfaces);
__mutex_init(&priv->mutex, "subsys mutex", key);
/*初始化2个内核链表*/
klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
klist_init(&priv->klist_drivers, NULL, NULL);
/*创建属性文件,即bus/xxx/建立文件drivers_autoprobe和drivers_probe*/
retval = add_probe_files(bus);
if (retval)
goto bus_probe_files_fail;
/*根据bus->bus_attribute创建属性，在bus/xxx/下建立相应的文件*/
retval = bus_add_groups(bus, bus->bus_groups);
if (retval)
goto bus_groups_fail;
pr_debug("bus: '%s': registered\n", bus->name);
return 0;
bus_groups_fail:
remove_probe_files(bus);
bus_probe_files_fail:
kset_unregister(bus->p->drivers_kset);
bus_drivers_fail:
kset_unregister(bus->p->devices_kset);
bus_devices_fail:
bus_remove_file(bus, &bus_attr_uevent);
bus_uevent_fail:
kset_unregister(&bus->p->subsys);
out:
kfree(bus->p);
bus->p = NULL;
return retval;
}
EXPORT_SYMBOL_GPL(bus_register);
三. device
3.1 简介
设备在内核中表示：
/*路径：include/linux/device.h*/
/**
* struct device - The basic device structure
* @parent: The device's "parent" device, the device to which it is attached.
* In most cases, a parent device is some sort of bus or host
* controller. If parent is NULL, the device, is a top-level device,
* which is not usually what you want.
* @p: Holds the private data of the driver core portions of the device.
* See the comment of the struct device_private for detail.
* @kobj: A top-level, abstract class from which other classes are derived.
* @init_name: Initial name of the device.
* @type: The type of device.
* This identifies the device type and carries type-specific
* information.
* @mutex: Mutex to synchronize calls to its driver.
* @bus: Type of bus device is on.
* @driver: Which driver has allocated this
* @platform_data: Platform data specific to the device.
* Example: For devices on custom boards, as typical of embedded
* and SOC based hardware, Linux often uses platform_data to point
* to board-specific structures describing devices and how they
* are wired. That can include what ports are available, chip
* variants, which GPIO pins act in what additional roles, and so
* on. This shrinks the "Board Support Packages" (BSPs) and
* minimizes board-specific #ifdefs in drivers.
* @driver_data: Private pointer for driver specific info.
* @power: For device power management.
* See Documentation/power/devices.txt for details.
* @pm_domain: Provide callbacks that are executed during system suspend,
* hibernation, system resume and during runtime PM transitions
* along with subsystem-level and driver-level callbacks.
* @pins: For device pin management.
* See Documentation/pinctrl.txt for details.
* @numa_node: NUMA node this device is close to.
* @dma_mask: Dma mask (if dma'ble device).
* @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
* hardware supports 64-bit addresses for consistent allocations
* such descriptors.
* @dma_pfn_offset: offset of DMA memory range relatively of RAM
* @dma_parms: A low level driver may set these to teach IOMMU code about
* segment limitations.
* @dma_pools: Dma pools (if dma'ble device).
* @dma_mem: Internal for coherent mem override.
* @cma_area: Contiguous memory area for dma allocations
* @archdata: For arch-specific additions.
* @of_node: Associated device tree node.
* @acpi_node: Associated ACPI device node.
* @devt: For creating the sysfs "dev".
* @id: device instance
* @devres_lock: Spinlock to protect the resource of the device.
* @devres_head: The resources list of the device.
* @knode_class: The node used to add the device to the class list.
* @class: The class of the device.
* @groups: Optional attribute groups.
* @release: Callback to free the device after all references have
* gone away. This should be set by the allocator of the
* device (i.e. the bus driver that discovered the device).
* @iommu_group: IOMMU group the device belongs to.
*
* @offline_disabled: If set, the device is permanently online.
* @offline: Set after successful invocation of bus type's .offline().
*
* At the lowest level, every device in a Linux system is represented by an
* instance of struct device. The device structure contains the information
* that the device model core needs to model the system. Most subsystems,
* however, track additional information about the devices they host. As a
* result, it is rare for devices to be represented by bare device structures;
* instead, that structure, like kobject structures, is usually embedded within
* a higher-level representation of the device.
*/
struct device {
struct device *parent;
struct device_private *p;
struct kobject kobj;
const char *init_name; /* initial name of the device */
const struct device_type *type;
struct mutex mutex; /* mutex to synchronize calls to
* its driver.
*/
struct bus_type *bus; /* type of bus device is on */
struct device_driver *driver; /* which driver has allocated this
device */
void *platform_data; /* Platform specific data, device
core doesn't touch it */
void *driver_data; /* Driver data, set and get with
dev_set/get_drvdata */
struct dev_pm_info power;
struct dev_pm_domain *pm_domain;
#ifdef CONFIG_PINCTRL
struct dev_pin_info *pins;
#endif
#ifdef CONFIG_NUMA
int numa_node; /* NUMA node this device is close to */
#endif
u64 *dma_mask; /* dma mask (if dma'able device) */
u64 coherent_dma_mask;/* Like dma_mask, but for
alloc_coherent mappings as
not all hardware supports
64 bit addresses for consistent
allocations 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 mem
override */
#ifdef CONFIG_DMA_CMA
struct cma *cma_area; /* contiguous memory area for dma
allocations */
#endif
struct removed_region *removed_mem;
/* arch specific additions */
struct dev_archdata archdata;
struct device_node *of_node; /* associated device tree node */
struct acpi_dev_node acpi_node; /* associated ACPI device node */
dev_t devt; /* dev_t, creates the sysfs "dev" */
u32 id; /* device instance */
spinlock_t devres_lock;
struct list_head devres_head;
struct klist_node knode_class;
struct class *class;
const struct attribute_group **groups; /* optional groups */
void (*release)(struct device *dev);
struct iommu_group *iommu_group;
bool offline_disabled:1;
bool offline:1;
};
/**
* struct device_private - structure to hold the private to the driver core portions of the device structure.
*
* @klist_children - klist containing all children of this device
* @knode_parent - node in sibling list
* @knode_driver - node in driver list
* @knode_bus - node in bus list
* @deferred_probe - entry in deferred_probe_list which is used to retry the
* binding of drivers which were unable to get all the resources needed by
* the device; typically because it depends on another driver getting
* probed first.
* @device - pointer back to the struct class that this structure is
* associated with.
*
* Nothing outside of the driver core should ever touch these fields.
*/
struct device_private {
struct klist klist_children;
struct klist_node knode_parent;
struct klist_node knode_driver;
struct klist_node knode_bus;
struct list_head deferred_probe;
struct device *device;
};
/*可得：
1. device本身包含一个kobject，也就是说这个device在sysfs的某个地方有着一个对应的目录。
2. 该device所挂载的bus由knode_bus指定。
3. 该device所对应的设备驱动由knode_driver指定。
*/
3.2 实例---platform_bus 虚拟平台设备
3.2.1 流程
platform_bus_init() /*路径：drivers/base/platform.c*/
device_register() /*路径：drivers/base/core.c*/
3.2.2 接口函数
/*1. platform_bus_init() 路径：drivers/base/platform.c*/
struct device platform_bus = {
.init_name = "platform",
};
EXPORT_SYMBOL_GPL(platform_bus);
int __init platform_bus_init(void)
{
int error;
early_platform_cleanup();
error = device_register(&platform_bus);
if (error)
return error;
error = bus_register(&platform_bus_type);
if (error)
device_unregister(&platform_bus);
return error;
}
/*2. device_register() 路径：drivers/base/core.c*/
/**
* 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.
*
* For more information, see the kerneldoc for device_initialize()
* and device_add().
*
* 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的某些字段*/
return device_add(dev); /*将设备添加到系统中*/
}
EXPORT_SYMBOL_GPL(device_register);
/*设备的注册都分为两步:
1. 设备的初始化
2. 添加到内核中
*/
/*3.设备初始化相关接口*/
/*3.1 初始化*/
/**
* device_initialize - init device structure.
* @dev: device.
*
* This prepares the device for use by other layers by initializing
* its fields.
* It is the first half of device_register(), if called by
* that function, though it can also be called separately, so one
* may use @dev's fields. In particular, get_device()/put_device()
* may be used for reference counting of @dev after calling this
* function.
*
* NOTE: Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.
*/
void device_initialize(struct device *dev)
{
dev->kobj.kset = devices_kset; /*设置kobj属于哪个kset。实际为：/sys/devices/ */
/*该函数在做了一系列的必要检查后，调用kobject_init_internal初始化了kobject的某些字段。*/
kobject_init(&dev->kobj, &device_ktype); /*初始化dev->kobj */
INIT_LIST_HEAD(&dev->dma_pools); /*初始化链表头*/
init_MUTEX(&dev->sem); /*初始化互斥体*/
spin_lock_init(&dev->devres_lock); /*初始化自旋锁*/
INIT_LIST_HEAD(&dev->devres_head); /*初始化链表头*/
/*设置电源的状态*/
device_pm_init(dev); /*设置该device可操作*/
/*如果使用NUMA，则设置NUMA节点*/
set_dev_node(dev, -1); /*设置NUMA节点*/
}
/*3.2 device_initialize()中所用的devices_kset 容器的创建*/
int __init devices_init(void)
{
devices_kset = kset_create_and_add("devices", &device_uevent_ops, NULL);
if (!devices_kset)
return -ENOMEM;
dev_kobj = kobject_create_and_add("dev", NULL);
if (!dev_kobj)
goto dev_kobj_err;
sysfs_dev_block_kobj = kobject_create_and_add("block", dev_kobj);
if (!sysfs_dev_block_kobj)
goto block_kobj_err;
sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
if (!sysfs_dev_char_kobj)
goto char_kobj_err;
return 0;
char_kobj_err:
kobject_put(sysfs_dev_block_kobj);
block_kobj_err:
kobject_put(dev_kobj);
dev_kobj_err:
kset_unregister(devices_kset);
return -ENOMEM;
}
/*
即：devices_kset对象表示的目录为/sys下的devices目录。
*/
/**4.设备添加相关接口**/
/**
* device_add - add device to device hierarchy.
* @dev: device.
*
* This is part 2 of device_register(), though may be called
* separately _iff_ device_initialize() has been called separately.
*
* This adds @dev to the kobject hierarchy via kobject_add(), adds it
* to the global and sibling lists for the device, then
* adds it to the other relevant subsystems of the driver model.
*
* Do not call this routine or device_register() more than once for
* any device structure. The driver model core is not designed to work
* with devices that get unregistered and then spring back to life.
* (Among other things, it's very hard to guarantee that all references
* to the previous incarnation of @dev have been dropped.) Allocate
* and register a fresh new struct device instead.
*
* NOTE: _Never_ directly free @dev after calling this function, even
* if it returned an error! Always use put_device() to give up your
* reference instead.
*/
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); /*增加引用计数*/
if (!dev)
goto done;
if (!dev->p) {
error = device_private_init(dev); /*初始化device_private结构*/
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); /*dev->kobject->name = dev->init_name*/
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);
/*检查dev->kobject->name*/
if (!dev_name(dev)) {
error = -EINVAL;
goto name_error;
}
pr_debug("device: '%s': %s\n", dev_name(dev), __func__);
parent = get_device(dev->parent); /*增加父设备引用计数*/
kobj = get_device_parent(dev, parent); /*设置dev->kobject->parent*/
if (kobj)
dev->kobj.parent = kobj;
/* use parent numa_node */
if (parent)
set_dev_node(dev, dev_to_node(parent));
/* first, register with generic layer. */
/* we require the name to be set before, and pass NULL */
/* 执行完以后，将在/sys/devices/下建立目录XXX，目录名XXX为dev->kobj->name*/
error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
if (error)
goto Error;
/* notify platform of device entry */
if (platform_notify)
platform_notify(dev);
/*在XXX下建立文件uevent*/
error = device_create_file(dev, &dev_attr_uevent);
if (error)
goto attrError;
if (MAJOR(dev->devt)) {
/*创建属性文件dev*/
error = device_create_file(dev, &dev_attr_dev);
if (error)
goto ueventattrError;
/* 在sys/dev/char/下建立symlink，名字为主设备号:次设备号，该链接指向XXX */
error = device_create_sys_dev_entry(dev);
if (error)
goto devtattrError;
devtmpfs_create_node(dev);
}
error = device_add_class_symlinks(dev);
if (error)
goto SymlinkError;
/*添加类设备属型文件和属性组*/
error = device_add_attrs(dev);
if (error)
goto AttrsError;
/*添加3个symlink*/
error = bus_add_device(dev);
if (error)
goto BusError;
/*创建power子目录，并在其下添加电源管理的属性组文件*/
error = dpm_sysfs_add(dev);
if (error)
goto DPMError;
if ((dev->pm_domain) || (dev->type && dev->type->pm)
|| (dev->class && (dev->class->pm || dev->class->resume))
|| (dev->bus && (dev->bus->pm || dev->bus->resume)) ||
(dev->driver && dev->driver->pm)) {
device_pm_add(dev); /*将该device添加到电源管理链表中*/
}
/* 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);
/*通知用户层*/
kobject_uevent(&dev->kobj, KOBJ_ADD);
/*将设备添加到总线的设备链表中，并尝试获取驱动*/
bus_probe_device(dev);
/*有父设备，则将该设备添加到父设备的儿子链表中*/
if (parent)
klist_add_tail(&dev->p->knode_parent,
&parent->p->klist_children);
/*该设备属于某个设备类*/
if (dev->class) {
mutex_lock(&dev->class->p->mutex);
/* tie the class to the device */
/*将device添加到class的类设备链表中*/
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);
}
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))
devtmpfs_delete_node(dev);
if (MAJOR(dev->devt))
device_remove_sys_dev_entry(dev);
devtattrError:
if (MAJOR(dev->devt))
device_remove_file(dev, &dev_attr_dev);
ueventattrError:
device_remove_file(dev, &dev_attr_uevent);
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;
}
EXPORT_SYMBOL_GPL(device_add);
结论：
当device_register调用完成以后，将在/sys/devices/下建立目录platform，并在platfrom下建立属性文件uevent和子目录power，最后在power子目录下建立wakeup属性文件。
四. driver
4.1 简介
驱动在内核中表示：
/**
* struct device_driver - The basic device driver structure
* @name: Name of the device driver.
* @bus: The bus which the device of this driver belongs to.
* @owner: The module owner.
* @mod_name: Used for built-in modules.
* @suppress_bind_attrs: Disables bind/unbind via sysfs.
* @of_match_table: The open firmware table.
* @acpi_match_table: The ACPI match table.
* @probe: Called to query the existence of a specific device,
* whether this driver can work with it, and bind the driver
* to a specific device.
* @remove: Called when the device is removed from the system to
* unbind a device from this driver.
* @shutdown: Called at shut-down time to quiesce the device.
* @suspend: Called to put the device to sleep mode. Usually to a
* low power state.
* @resume: Called to bring a device from sleep mode.
* @groups: Default attributes that get created by the driver core
* automatically.
* @pm: Power management operations of the device which matched
* this driver.
* @p: Driver core's private data, no one other than the driver
* core can touch this.
*
* The device driver-model tracks all of the drivers known to the system.
* The main reason for this tracking is to enable the driver core to match
* up drivers with new devices. Once drivers are known objects within the
* system, however, a number of other things become possible. Device drivers
* can export information and configuration variables that are independent
* of any specific device.
*/
struct device_driver {
const char *name;
struct bus_type *bus;
struct module *owner;
const char *mod_name; /* used for built-in modules */
bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
const struct of_device_id *of_match_table;
const struct acpi_device_id *acpi_match_table;
int (*probe) (struct device *dev);
int (*remove) (struct device *dev);
void (*shutdown) (struct device *dev);
int (*suspend) (struct device *dev, pm_message_t state);
int (*resume) (struct device *dev);
const struct attribute_group **groups;
const struct dev_pm_ops *pm;
struct driver_private *p;
};
struct driver_private {
struct kobject kobj;
struct klist klist_devices;
struct klist_node knode_bus;
struct module_kobject *mkobj;
struct device_driver *driver;
};
/*可得：
1. device_driver本身包含一个kobject，也就是说这个device_driver在sysfs的某个地方有着一个对应的目录。
2. 该设备驱动所支持的设备由klist_devices指定。
3. 该设备驱动所挂载的总线由knode_bus制定
*/
4.2 实例
/*1.驱动注册*/
/**
* platform_driver_probe - register driver for non-hotpluggable device
* @drv: platform driver structure
* @probe: the driver probe routine, probably from an __init section
*
* Use this instead of platform_driver_register() when you know the device
* is not hotpluggable and has already been registered, and you want to
* remove its run-once probe() infrastructure from memory after the driver
* has bound to the device.
*
* One typical use for this would be with drivers for controllers integrated
* into system-on-chip processors, where the controller devices have been
* configured as part of board setup.
*
* Note that this is incompatible with deferred probing.
*
* Returns zero if the driver registered and bound to a device, else returns
* a negative error code and with the driver not registered.
*/
int __init_or_module platform_driver_probe(struct platform_driver *drv,
int (*probe)(struct platform_device *))
{
int retval, code;
/*
* Prevent driver from requesting probe deferral to avoid further
* futile probe attempts.
*/
drv->prevent_deferred_probe = true;
/* make sure driver won't have bind/unbind attributes */
drv->driver.suppress_bind_attrs = true;
/* temporary section violation during probe() */
drv->probe = probe;
/*注册platform驱动*/
retval = code = platform_driver_register(drv);
/*
* Fixup that section violation, being paranoid about code scanning
* the list of drivers in order to probe new devices. Check to see
* if the probe was successful, and make sure any forced probes of
* new devices fail.
*/
spin_lock(&drv->driver.bus->p->klist_drivers.k_lock);
drv->probe = NULL;
if (code == 0 && list_empty(&drv->driver.p->klist_devices.k_list))
retval = -ENODEV;
drv->driver.probe = platform_drv_probe_fail;
spin_unlock(&drv->driver.bus->p->klist_drivers.k_lock);
if (code != retval)
platform_driver_unregister(drv);
return retval;
}
EXPORT_SYMBOL_GPL(platform_driver_probe);
/*2. 注册*/
/**
* __platform_driver_register - register a driver for platform-level devices
* @drv: platform driver structure
* @owner: owning module/driver
*/
int __platform_driver_register(struct platform_driver *drv,
struct module *owner)
{
drv->driver.owner = owner;
drv->driver.bus = &platform_bus_type;
if (drv->probe)
drv->driver.probe = platform_drv_probe;
if (drv->remove)
drv->driver.remove = platform_drv_remove;
if (drv->shutdown)
drv->driver.shutdown = platform_drv_shutdown;
return driver_register(&drv->driver);
}
EXPORT_SYMBOL_GPL(__platform_driver_register);
#define platform_driver_register(drv) \
__platform_driver_register(drv, THIS_MODULE)
/*注：
driver_register函数就是driver注册的核心函数。需要注意的是，在调用函数之前，
将该驱动所挂载的总线设置为platform总线（platform_bus_type）。
*/
/*3.驱动注册*/
/**
* 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.
*/
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);
/*用驱动名字来搜索在该总线上驱动是否已经存在*/
other = driver_find(drv->name, drv->bus);
if (other) {
printk(KERN_ERR "Error: Driver '%s' is already registered, "
"aborting...\n", drv->name);
return -EBUSY;
}
/*将驱动添加到一个总线中*/
ret = bus_add_driver(drv);
if (ret)
return ret;
/*建立属性组文件*/
ret = driver_add_groups(drv, drv->groups);
if (ret) {
bus_remove_driver(drv);
return ret;
}
kobject_uevent(&drv->p->kobj, KOBJ_ADD);
return ret;
}
EXPORT_SYMBOL_GPL(driver_register);
/*4. 将驱动加入到bus中*/
/**
* bus_add_driver - Add a driver to the bus.
* @drv: driver.
*/
int bus_add_driver(struct device_driver *drv)
{
struct bus_type *bus;
struct driver_private *priv;
int error = 0;
/*增加引用计数获取bus_type*/
bus = bus_get(drv->bus);
if (!bus)
return -EINVAL;
pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
/*分配driver_private结构体*/
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv) {
error = -ENOMEM;
goto out_put_bus;
}
/*初始化内核链表*/
klist_init(&priv->klist_devices, NULL, NULL);
/*相互保存*/
priv->driver = drv;
drv->p = priv;
/*设置该kobj属于那个kset*/
priv->kobj.kset = bus->p->drivers_kset;
/*parent=NULL*/
/*执行完以后，会在bus/总线名/drivers/下建立名为drv->name的目录*/
error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
"%s", drv->name);
if (error)
goto out_unregister;
/*添加该驱动到bus的内核链表中*/
klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
if (drv->bus->p->drivers_autoprobe) {
/*尝试绑定驱动和设备*/
error = driver_attach(drv);
if (error)
goto out_unregister;
}
module_add_driver(drv->owner, drv);
/*创建属性，在bus/总线名/drivers/驱动名/下建立文件uevent*/
error = driver_create_file(drv, &driver_attr_uevent);
if (error) {
printk(KERN_ERR "%s: uevent attr (%s) failed\n",
__func__, drv->name);
}
/*利用bus->drv_groups创建属性，位于bus/总线名/drivers/驱动名/*/
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);
}
/*创建属性，在bus/总线名/drivers/驱动名/下建立文件bind和unbind*/
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;
out_unregister:
kobject_put(&priv->kobj);
kfree(drv->p);
drv->p = NULL;
out_put_bus:
bus_put(bus);
return error;
}
来源：CSDN
作者：vertor11
链接：https://blog.csdn.net/vertor11/article/details/103748942