Linux驱动之设备模型(6)

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7．设备驱动

7.1 设备驱动

l 在Linux设备模型中，设备驱动用device_driver结构来表示

structdevice_driver {

const char *name; /*名字*/

struct bus_type *bus; /* 附属的总线 */

struct module *owner;

const struct of_device_id *of_match_table;

int (*probe) (struct device *dev); /* 设备与驱动匹配时调用 */

int (*remove) (struct device *dev); /* 设备移除时调用 */

void (*shutdown) (struct device *dev);

int (*suspend) (struct device *dev,pm_message_t state);

int (*resume) (struct device *dev);

const struct attribute_group **groups; /* 属性组 */

/*电源管理操作*/

const struct dev_pm_ops *pm;

struct driver_private *p; /* 私有数据：内嵌的kobject，设备链表，总线链表节点*/

};

7.2 驱动属性

l 驱动属性由driver_attribute来表示

structdriver_attribute {

struct attribute attr;

ssize_t (*show)(struct device_driver*driver, char *buf);

ssize_t (*store)(struct device_driver*driver, const char *buf,

size_t count);

};

DRIVER_ATTR(_name,_mode, _show, _store)

l 属性操作

n 创建属性

intdriver_create_file(struct device_driver *driver,

const structdriver_attribute *attr);

n 删除属性

voiddriver_remove_file(struct device_driver *driver,

const struct driver_attribute *attr);

7.3 驱动基本操作

l 驱动注册和注销

int driver_register(struct device_driver *drv)

void driver_unregister(struct device_driver *drv)

l 驱动注册分析

n driver_register

intdriver_register(struct device_driver *drv)

{

int ret;

struct device_driver *other;

BUG_ON(!drv->bus->p);

/* 检查是否定义了probe，remove，shutdown方法 */

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_typemethods\n", drv->name);

/* 检查总线上是否已经注册了此驱动 */

other = driver_find(drv->name,drv->bus);

if (other) {

put_driver(other);

}

/* 向总线添加驱动，稍后重点分析 */

ret = bus_add_driver(drv);

/* 添加相应属性 */

ret = driver_add_groups(drv, drv->groups);

}

n bus_add_driver

intbus_add_driver(struct device_driver *drv)

{

/* 引用计数加1 */

bus = bus_get(drv->bus);

/* 初始化和添加kobject */

error =kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,

"%s", drv->name);

if(drv->bus->p->drivers_autoprobe) {

error = driver_attach(drv);

}

/* 把驱动关联到总线的驱动链表中 */

klist_add_tail(&priv->knode_bus,&bus->p->klist_drivers);

/* 创建属性 */

error = driver_create_file(drv,&driver_attr_uevent);

error = driver_add_attrs(bus, drv);

/* 向用户空间发送KOBJ_ADDuevent */

kobject_uevent(&priv->kobj,KOBJ_ADD);

}

n driver_attach

int driver_attach(structdevice_driver *drv)

{

return bus_for_each_dev(drv->bus,NULL, drv, __driver_attach);

}

遍历总线上的所有设备，当有驱动支持的设备时，调用__driver_attach函数完成相应的工作__driver_attach()->driver_probe_device()->driver_probe_device()->bus->probe()->

drv->probe () 优先调用总线中定义的probe函数，如果bus中未定义probe，则再调用驱动中定义的probe。

7.4 实例分析

* for learn driver

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/device.h>

#include <linux/string.h>

extern struct bus_type scbus_type;

static char *Version = "revision 1.0,scdriver";

static int sc_probe(struct device *dev)

{

printk("driverfound device\n");

return0;

}

static int sc_remove(struct device *dev)

{

printk("deviceremove\n");

return0;

}

struct device_driver scdriver = {

.name = "scdevice0", /* 驱动名字，用来匹配支持的设备 */

.bus = &scbus_type, /* 依附的总线类型 */

.probe = sc_probe, /* 设备和驱动匹配时调用 */

.remove = sc_remove, /* 设备移除时调用 */

};

* export driver attribute

static ssize_t driver_show_version(structdevice_driver *driver, char *buf)

{

returnsprintf(buf, "%s\n", Version);

}

static DRIVER_ATTR(version, S_IRUGO,driver_show_version, NULL);

static int __init scdriver_init(void)

{

intret;

/* 注册驱动 */

ret= driver_register(&scdriver);

if(ret)

returnret;

/*创建属性 */

ret= driver_create_file(&scdriver, &driver_attr_version);

if(ret)

gotoerr_create;

printk("drvierregistered\n");

return0;

err_create:

driver_unregister(&scdriver);

returnret;

}

static void __exit scdriver_exit(void)

{

driver_remove_file(&scdriver,&driver_attr_version);

driver_unregister(&scdriver);

}

module_init(scdriver_init);

module_exit(scdriver_exit);

MODULE_LICENSE("Dual BSD/GPL");

MODULE_AUTHOR("CJOK<cjok.liao@gmail.com>");

试验结果：