一、重要知识点:
设备模型由总线、设备、驱动三要素组成。
底层模型决定上层模型,在总线,设备,驱动的结构体中你总是可以看到它们间接或者直接的包含了kobject结构或kset结构。
1.总线
总线是处理器和设备之间的通道,在设备模型中,所有设备都通过总线相连,甚至内部的虚拟“platform”总线。在linux设备模型中,总线由bus_type结构表示。定义在<linux/device>中。
总线描述
-
struct bus_type {
-
const char *name;//总线名称
-
struct bus_attribute *bus_attrs//总线属性
-
struct device_attribute *dev_attrs;//设备属性
-
struct driver_attribute *drv_attrs;//驱动属性
-
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 (*suspend)(struct device *dev, pm_message_t state);
-
int (*suspend_late)(struct device *dev, pm_message_t state);
-
int (*resume_early)(struct device *dev);
-
int (*resume)(struct device *dev);
-
struct dev_pm_ops *pm;
-
struct bus_type_private *p;
-
};
bus_type的bus_type_private 成员
-
struct bus_type_private {
-
struct kset subsys;
-
struct kset *drivers_kset;
-
struct kset *devices_kset;
-
struct klist klist_devices;
-
struct klist klist_drivers;
-
struct blocking_notifier_head bus_notifier;
-
unsigned int drivers_autoprobe:1;
-
struct bus_type *bus;
-
};
可以看出该结构体中包含了有device和dirver的kset对象。
总线的注册:
int bus_register(structbus_type *bus);
如果成功,新的总线将被添加到系统,在/sys/bus目录下可以看到。
我们在深入看这个函数
-
int bus_register(struct bus_type *bus)
-
{
-
int retval;
-
struct bus_type_private *priv;
-
priv = kzalloc(sizeof(struct bus_type_private), GFP_KERNEL);
-
if (!priv)
-
return -ENOMEM;
-
priv->busbus = 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);
-
if (retval)
-
goto out;
-
-
retval = bus_create_file(bus, &bus_attr_uevent);
-
if (retval)
-
goto bus_uevent_fail;
-
-
-
priv->devices_kset = kset_create_and_add("devices", NULL,
-
&priv->subsys.kobj);
-
if (!priv->devices_kset) {
-
retval = -ENOMEM;
-
goto bus_devices_fail;
-
}
-
-
-
priv->drivers_kset = kset_create_and_add("drivers", NULL,
-
&priv->subsys.kobj);
-
if (!priv->drivers_kset) {
-
retval = -ENOMEM;
-
goto bus_drivers_fail;
-
}
-
-
-
klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
-
klist_init(&priv->klist_drivers, NULL, NULL);
-
-
retval = add_probe_files(bus);
-
if (retval)
-
goto bus_probe_files_fail;
-
-
retval = bus_add_attrs(bus);
-
if (retval)
-
goto bus_attrs_fail;
-
-
pr_debug("bus: '%s': registered\n", bus->name);
-
return 0;
-
-
bus_attrs_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);
-
kfree(bus->p);
-
out:
-
return retval;
-
}
从这里
priv->subsys.kobj.kset = bus_kset;
priv->subsys.kobj.ktype = &bus_ktype;
可以看得出总线初始化了自己的kset对象。
总线的删除
void bus_unregister(struct bus_type *bus);
总线的match方法
int (*match)(struct device *dev, struct device_driver *drv);
当一个新设备或者驱动被添加到这个总线时,该方法被调用,用于判断指定的驱动程序是否能处理指定的设备。若可以,则返回非0值。下面的测试程序采用匹配设备的dev->bus_id字符串和驱动的drv->name字符串是否相同来判断驱动是否能处理该设备。
总线uevent方法
int (*uevent)(structdevice *dev, char **envp, int num_envp)
在为用户产生热插拔事件之前,这个方法允许总线添加环境变量。
总线属性由结构bus_attribute描述:
struct bus_attribute {
struct attribute attr;
ssize_t (*show)(struct bus_type *bus,char *buf);
ssize_t (*store)(struct bus_type *bus,const char *buf, size_t count);
};
BUS_ATTR(name,mode, show, store)
在编译时创建和初始化bus_attribute结构,它将bus_attr_作为给定前缀来创建总线的真正名称。
如:static BUS_ATTR(version, S_IRUGO, show_bus_version, NULL);
将创建一个bus_attr_version结构体对象。
int bus_create_file(struct bus_type *bus, struct bus_attribute *attr)
创建属性文件
void bus_remove_file(struct bus_type *bus, struct bus_attribute *attr)
删除属性文件
2.设备
-
struct device {
-
struct klist klist_children;
-
struct klist_nodeknode_parent;/* node in sibling list */
-
struct klist_nodeknode_driver;
-
struct klist_nodeknode_bus;
-
struct device *parent;
-
struct kobject kobj;
-
char bus_id[BUS_ID_SIZE];/* position on parent bus */
-
unsigned uevent_suppress:1;
-
const char *init_name; /* initial name of the device */
-
struct device_type*type;
-
-
struct semaphoresem;/* semaphore 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 *driver_data;/* data private to the driver */
-
void *platform_data;/* Platform specific data, device
-
core doesn't touch it */
-
struct dev_pm_infopower;
-
-
-
#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. */
-
-
-
struct device_dma_parameters *dma_parms;
-
-
-
struct list_headdma_pools;/* dma pools (if dma'ble) */
-
-
-
struct dma_coherent_mem*dma_mem; /* internal for coherent mem
-
override */
-
/* arch specific additions */
-
struct dev_archdataarchdata;
-
-
dev_t devt;/* dev_t, creates the sysfs "dev" */
-
-
spinlock_t devres_lock;
-
struct list_headdevres_head;
-
-
-
struct klist_nodeknode_class;
-
struct class *class;
-
struct attribute_group**groups;/* optional groups */
-
-
void (*release)(struct device *dev);
-
};
可以看出device结构体中也包含了一个kobject对象
intdevice_register(struct device *dev);
注册设备
vioddevice_unregister(struct device *dev)
注销设备
设备属性由struct device_attribute描述
structdevice_attribute {
struct attribute attr;
ssize_t (*show)(struct device *dev,struct device_attribute *attr,
char *buf);
ssize_t (*store)(struct device *dev,struct device_attribute *attr,
const char *buf, size_t count);
};
int device_create_file(struct device *dev, struct device_attibute *entry)
创建属性文件
void device_remove_file(struct device *dev, struct device_attibute *entry)
删除属性文件
3.驱动
驱动程序由struct device_driver描述:
-
struct device_driver {
-
const char *name;
-
struct bus_type*bus;
-
-
-
struct module *owner;
-
const char *mod_name;/* used for built-in modules */
-
-
-
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);
-
struct attribute_group **groups;
-
-
-
struct dev_pm_ops *pm;
-
-
-
struct driver_private *p;
-
};
在看device_dirver的driver_private 对象
struct driver_private {
struct kobject kobj;
struct klist klist_devices;
struct klist_node knode_bus;
struct module_kobject *mkobj;
struct device_driver *driver;
};
可以看出driver_private结构体中也包含了一个kobject对象。和连接设备的链表。
当总线的match返回非0值,也就是总线找到与驱动相匹配的设备时,驱动的probe的函数将被调用。
当设备从系统总删除是remove被调用。
当系统关机的时候shutdown被调用。
int driver_register(structdevice_driver *drv)
在总线上注册驱动
void driver_unregister(struct device_driver *drv)
载总线上注销驱动
驱动的属性使用structdriver_attribute来描述
structdriver_attribute{
structattribue attr;
ssize_t(*show)(struct device_driver *drv, const char *buf);
ssize_t(*store)(struct device_driver *drv, const char *buf, size_t count);
}
int dirver_create_file(struct device_driver *drv, struct driver_attribute *attr);
创建属性文件
void driver_remove_file struct device_driver *drv, struct driver_attribute *attr);
删除属性文件
二、测试模块
1.BUS
-
#include <linux/device.h>
-
#include <linux/module.h>
-
#include <linux/kernel.h>
-
#include <linux/init.h>
-
#include <linux/string.h>
-
-
MODULE_AUTHOR("David Xie");
-
MODULE_LICENSE("Dual BSD/GPL");
-
-
static char *Version = "$Revision: 1.9 {1}quot;;
-
-
static int my_match(struct device *dev, struct device_driver *driver)
-
{
-
return !strncmp(dev->bus_id, driver->name, strlen(driver->name));
-
}
-
-
static void my_bus_release(struct device *dev)
-
{
-
printk(KERN_DEBUG "my bus release\n");
-
}
-
-
struct device my_bus = {
-
.bus_id = "my_bus0",
-
.release = my_bus_release
-
};
-
-
-
struct bus_type my_bus_type = {
-
.name = "my_bus",
-
.match = my_match,
-
};
-
-
EXPORT_SYMBOL(my_bus);
-
EXPORT_SYMBOL(my_bus_type);
-
-
-
/*
-
* Export a simple attribute.
-
*/
-
static ssize_t show_bus_version(struct bus_type *bus, char *buf)
-
{
-
return snprintf(buf, PAGE_SIZE, "%s\n", Version);
-
}
-
-
static BUS_ATTR(version, S_IRUGO, show_bus_version, NULL);
-
-
-
static int __init my_bus_init(void)
-
{
-
int ret;
-
-
/*注册总线*/
-
ret = bus_register(&my_bus_type);
-
if (ret)
-
return ret;
-
-
/*创建属性文件*/
-
if (bus_create_file(&my_bus_type, &bus_attr_version))
-
printk(KERN_NOTICE "Fail to create version attribute!\n");
-
-
/*注册总线设备*/
-
ret = device_register(&my_bus);
-
if (ret)
-
printk(KERN_NOTICE "Fail to register device:my_bus!\n");
-
-
return ret;
-
}
-
-
static void my_bus_exit(void)
-
{
-
device_unregister(&my_bus);
-
bus_unregister(&my_bus_type);
-
}
-
-
module_init(my_bus_init);
-
module_exit(my_bus_exit);
创建一条名为my_bus_type的总线和一个名为my_bus的总线设备,注意总线也是一个设备,也需要注册。
测试结果:
2.DEVICE
-
#include <linux/device.h>
-
#include <linux/module.h>
-
#include <linux/kernel.h>
-
#include <linux/init.h>
-
#include <linux/string.h>
-
-
MODULE_AUTHOR("David Xie");
-
MODULE_LICENSE("Dual BSD/GPL");
-
-
extern struct device my_bus;
-
extern struct bus_type my_bus_type;
-
-
/* Why need this ?*/
-
static void my_dev_release(struct device *dev)
-
{
-
-
}
-
-
struct device my_dev = {
-
.bus = &my_bus_type,
-
.parent = &my_bus,
-
.release = my_dev_release,
-
};
-
-
/*
-
* Export a simple attribute.
-
*/
-
static ssize_t mydev_show(struct device *dev, char *buf)
-
{
-
return sprintf(buf, "%s\n", "This is my device!");
-
}
-
-
static DEVICE_ATTR(dev, S_IRUGO, mydev_show, NULL);
-
-
static int __init my_device_init(void)
-
{
-
int ret = 0;
-
-
/* 初始化设备 */
-
strncpy(my_dev.bus_id, "my_dev", BUS_ID_SIZE);
-
-
/*注册设备*/
-
device_register(&my_dev);
-
-
/*创建属性文件*/
-
device_create_file(&my_dev, &dev_attr_dev);
-
-
return ret;
-
-
}
-
-
static void my_device_exit(void)
-
{
-
device_unregister(&my_dev);
-
}
-
-
module_init(my_device_init);
-
module_exit(my_device_exit);
注册一个bus_id即名字为my_dev的设备,该设备的bus成员指向上一步创建的my_bus_type总线,parent成员指向上一步创建的my_bus总线设备。
测试结果:
3.DRIVER
-
#include <linux/device.h>
-
#include <linux/module.h>
-
#include <linux/kernel.h>
-
#include <linux/init.h>
-
#include <linux/string.h>
-
-
MODULE_AUTHOR("David Xie");
-
MODULE_LICENSE("Dual BSD/GPL");
-
-
extern struct bus_type my_bus_type;
-
-
static int my_probe(struct device *dev)
-
{
-
printk("Driver found device which my driver can handle!\n");
-
return 0;
-
}
-
-
static int my_remove(struct device *dev)
-
{
-
printk("Driver found device unpluged!\n");
-
return 0;
-
}
-
-
struct device_driver my_driver = {
-
.name = "my_dev",
-
.bus = &my_bus_type,
-
.probe = my_probe,
-
.remove = my_remove,
-
};
-
-
/*
-
* Export a simple attribute.
-
*/
-
static ssize_t mydriver_show(struct device_driver *driver, char *buf)
-
{
-
return sprintf(buf, "%s\n", "This is my driver!");
-
}
-
-
static DRIVER_ATTR(drv, S_IRUGO, mydriver_show, NULL);
-
-
static int __init my_driver_init(void)
-
{
-
int ret = 0;
-
-
/*注册驱动*/
-
driver_register(&my_driver);
-
-
/*创建属性文件*/
-
driver_create_file(&my_driver, &driver_attr_drv);
-
-
return ret;
-
-
}
-
-
static void my_driver_exit(void)
-
{
-
driver_unregister(&my_driver);
-
}
-
-
module_init(my_driver_init);
-
module_exit(my_driver_exit);
创建一个名为“bus_dev”的驱动,并将bus成员指向第一步创建的my_bus_type总线
测试结果: