Linux的sysfs与驱动模型体会1

使用的linux版本是2.6.181、概念与重要的数据结构SYSFS是一个虚拟的文件系统，这个文件系统的目录结构实质上就是内核对象模型树。Kobject:内核对象，是模型树中的基本组成单位
53 struct kobject {54 const char * k_name;55 char name[KOBJ_NAME_LEN];56 struct kref kref;57 struct list_head entry;58 struct kobject * parent;59 struct kset * kset;60 struct kobj_type * ktype;61 struct dentry * dentry;62 wait_queue_head_t poll;63 };kset:对象集合127 struct kset {128 struct subsystem * subsys;129 struct kobj_type * ktype;130 struct list_head list;131 spinlock_t list_lock;132 struct kobject kobj;133 struct kset_uevent_ops * uevent_ops;134 };ktype:描述kobject的属性，可通过对属性的操作来作一些信息的获取或更改96 struct kobj_type {97 void （*release）（struct kobject *）;98 struct sysfs_ops * sysfs_ops;99 struct attribute ** default_attrs;100 };subsystem:子系统，实则上是一个kset，在高层次的概念176 struct subsystem {177 struct kset kset;178 struct rw_semaphore rwsem;179 };2、结构图<参见LDD3的sysfs部分> 关于kset与kobject之间的关系图。从该图可以看出，结构的组成，主要就是kset和kobject来组成各种高层次的结构。3、bus子系统基本结构38 struct bus_type {39 const char * name;40 41 struct subsystem subsys;42 struct kset drivers;43 struct kset devices;44 struct klist klist_devices;45 struct klist klist_drivers;46 47 struct blocking_notifier_head bus_notifier;48 49 struct bus_attribute * bus_attrs;50 struct device_attribute * dev_attrs;51 struct driver_attribute * drv_attrs;52 53 int （*match）（struct device * dev, struct device_driver * drv）;54 int （*uevent）（struct device *dev, char **envp,55 int num_envp, char *buffer, int buffer_size）;56 int （*probe）（struct device * dev）;57 int （*remove）（struct device * dev）;58 void （*shutdown）（struct device * dev）;59 60 int （*suspend）（struct device * dev, pm_message_t state）;61 int （*suspend_late）（struct device * dev, pm_message_t state）;62 int （*resume_early）（struct device * dev）;63 int （*resume）（struct device * dev）;64 };bus_type内嵌了一个 subsystem subsys,所以bus_type可以看作是一个类子系统，实则上就是一个子系统。通过分析i2c总线的注册过程和对应在sysfs中的目录结构来看。bus_type – i2c_bus_type在/sys/目录下，看到目录实际上对应一个子系统。而我们要在这些子系统下新建一些子系统，对于i2c总线，我们要在bus子系统下挂接我们的i2c子系统。通过bus_register（&i2c_bus_type）来完成这一操作。具体的操作实际上就是插入一个kobject。（１）对i2c的sub_sys的kobject设置名称，唯一的名称，这个名称会在/sys/bus/下看到。kobject_set_name（i2c_bus_type.sub_sys.kset.kobject）;（２）然后就是设置这个子系统的父结点，也就是设定这个子系统的父子系统。所有总线的父子系统都是bus_subsys。i2c_bus_type.sub_sys.kset.kobject.kset = bus_subsys.kset（３）最后将i2c_bus_type子系统加入到bus_subsys集合内的子系统链表中。i2c_bus_type.sub_sys.kset.kobject.parent = bus_subsys.kset.kobject add_list_tail（i2c_bus_type.sub_sys.kset.kobject.entry, bus_subsys.kset.list）以上的操作，基本上把i2c_bus_type对应的子系统加入到bus_subsys下面了，在/sys/bus/下面可以看到i2c目录。在bus_type中可以看到有两个kset,drivers和devices。这两个kset属于i2c子系统下的两个集合。所以将这两个kset挂接到i2c子系统下面。
（4）挂接devices到i2c子系统下面，完成后可在/sys/bus/i2c下看到devices目录kobject_set_name（devices.kobject, “devices”）;devices.subsys = &i2c_bus_type.sub_sys;devices.kobject.parent = i2c_bus_type.sub_sys.kset.kobjectadd_list_tail（devices.kobject, i2c_bus_type.sub_sys.kset.list）;
（5）同理，挂接drivers到i2c子系统下面，完成后可在/sys/bus/i2c下看到drivers目录kobject_set_name（devices.kobject, “devices”）;devices.subsys = &i2c_bus_type.sub_sys;devices.kobject.parent = i2c_bus_type.sub_sys.kset.kobjectadd_list_tail（devices.kobject, i2c_bus_type.sub_sys.kset.list）;4、bus子系统的设备与驱动394 struct device {395 struct klist klist_children;396 struct klist_node knode_parent; /* node in sibling list */397 struct klist_node knode_driver;398 struct klist_node knode_bus;399 struct device * parent;400 401 struct kobject kobj;402 char bus_id[BUS_ID_SIZE]; /* position on parent bus */403 struct device_type *type;404 unsigned is_registered:1;405 struct device_attribute uevent_attr;406 struct device_attribute *devt_attr;407 408 struct semaphore sem; /* semaphore to synchronize calls to409 * its driver.410 */411 412 struct bus_type * bus; /* type of bus device is on */413 struct device_driver *driver; /* which driver has allocated this414 device */415 void *driver_data; /* data private to the driver */416 void *platform_data; /* Platform specific data, device417 core doesn"t touch it */418 struct dev_pm_info power;420 #ifdef CONFIG_NUMA421 int numa_node; /* NUMA node this device is close to */422 #endif423 u64 *dma_mask; /* dma mask （if dma"able device） */424 u64 coherent_dma_mask;/* Like dma_mask, but for425 alloc_coherent mappings as426 not all hardware supports427 64 bit addresses for consistent428 allocations such descriptors. */429 430 struct list_head dma_pools; /* dma pools （if dma"ble） */431 432 struct dma_coherent_mem *dma_mem; /* internal for coherent mem433 override */434 /* arch specific additions */435 struct dev_archdata archdata;436 437 spinlock_t devres_lock;438 struct list_head devres_head;439 440 /* class_device migration path */441 struct list_head node;442 struct class *class;443 dev_t devt; /* dev_t, creates the sysfs "dev" */444 struct attribute_group **groups; /* optional groups */445 int uevent_suppress;446 447 void （*release）（struct device * dev）;448 };120 struct device_driver { 121 const char * name;122 struct bus_type * bus;123 124 struct completion unloaded;125 struct kobject kobj;126 struct klist klist_devices;127 struct klist_node knode_bus;128 129 struct module * owner;130 const char * mod_name; /* used for built-in modules */131 struct module_kobject * mkobj;132 133 int （*probe）（struct device * dev）; 134 int （*remove）（struct device * dev）;135 void （*shutdown）（struct device * dev）;136 int （*suspend）（struct device * dev, pm_message_t state）;137 int （*resume）（struct device * dev）;138 139 unsigned int multithread_probe:1;140 };注册驱动程序：driver_register（&i2c_adapter_driver）;i2c_adapter_driver内嵌了一个kobject，也就是说它将以一个kobject的模型挂接在系统的模型树里，在sysfs中，作为一个目录节点。kobject_set_name（i2c_adapter_driver.kobject, i2c_adatpter_driver.name）i2c_adapter_driver.kobject.kset = i2c_adapter_driver.bus->sub_sys.ksetadd_list_tail（i2c_adapter_driver.kobject, i2c_adapter_driver.kobject.kset.klist）