Linux设备驱动工程师之路——设备模型（下）上层模型
Linux设备驱动工程师之路——设备模型（下）上层模型
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转载请注明来自于衡阳师范学院08电2 Y-Kee http://blog.csdn.net/ayangke,QQ:843308498
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->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);
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：