设备模型元素:
1, 总线
2, 驱动
3, 设备
下面讲设备;
设备:
设备描述:
Linux 系统中的每个设备由一个 struct device 描述:
struct device 结构:
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsISN0MDO1IjMwIzMwUDMzEDMy8CX0Vmbu4GZzNmLn9Gbi1yZtl2Lc9CX6MHc0RHaiojIsJye.jpg)
设备 注册 / 注销 device_register device_unregister :
int device_register ( struct device *dev )
注册设备;
void device_unregister ( struct device *dev )
注销设备;
一条总线也是个设备,也必须按设备注册;
设备属性 :
struct device_attribute 结构:
设备属性使用 struct device_attribute 来描述:
struct device_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);
};
创建 / 删除 device_create_file device_remove_file :
int device_create_file ( struct device *device , struct device_attribute * entry)
创建属性;
void device_remove_file ( struct device * dev, struct device_attribute * attr )
删除属性;
下面是一个例子,包含两个文件:bus.c 和 device.c
bus.c 文件如下:
#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 $";
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);
device.c 文件如下:
#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);
测试结果:
先 insmod bus.ko ,查看发现 bus 目录下多了 my_bus 目录,
再查看 my_bus 下的 devices 目录,发现没有文件;
再加载 insmod device.ko ,
再查看 my_bus 下的 devices 目录,发现有 my_dev 链接文件