设备模型之设备

例子

bus.c

#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/*release函数在设备拔出后会被调用，如果是驱动卸载后不会被调用，只有在驱动先卸载，在拔出设备的时候才会被调用*/
};




struct bus_type my_bus_type = {
.name = "my_bus",
.match = my_match,
};


EXPORT_SYMBOL(my_bus);/*EXPORT_SYMBOL可以将一个函数以符号的方式导出给其他模块使用 。*/
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

#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,/*总线也是一个设备*/
.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);/*将字符串my_dev中最多BUS_ID_SIZE个字符复制到字符数组my_dev.bus_id中*/
        
        /*注册设备*/
device_register(&my_dev);

/*创建属性文件*/
device_create_file(&my_dev, &dev_attr_dev);/*DEVICE_ATTR定义*/

return ret;


}


static void my_device_exit(void)
{
device_unregister(&my_dev);
}


module_init(my_device_init);
module_exit(my_device_exit);