裝置模型元素:
1, 總線
2, 驅動
3, 裝置
下面講裝置;
裝置:
裝置描述:
Linux 系統中的每個裝置由一個 struct device 描述:
struct device 結構:
裝置 注冊 / 登出 device_register device_unregister :
int device_register ( struct device *dev )
注冊裝置;
void device_unregister ( struct device *dev )
登出裝置;
一條總線也是個裝置,也必須按裝置注冊;
裝置屬性 :
struct device_attribute 結構:
裝置屬性使用 struct device_attribute 來描述:
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);
};
建立 / 删除 device_create_file device_remove_file :
int device_create_file ( struct device *device , struct device_attribute * entry)
建立屬性;
void device_remove_file ( struct device * dev, struct device_attribute * attr )
删除屬性;
下面是一個例子,包含兩個檔案:bus.c 和 device.c
bus.c 檔案如下:
#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;
/*注冊總線*/
ret = bus_register(&my_bus_type);
if (ret)
return ret;
/*建立屬性檔案*/
if (bus_create_file(&my_bus_type, &bus_attr_version))
printk(KERN_NOTICE "Fail to create version attribute!\n");
/*注冊總線裝置*/
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 檔案如下:
#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;
/* 初始化裝置 */
strncpy(my_dev.bus_id, "my_dev", BUS_ID_SIZE);
/*注冊裝置*/
device_register(&my_dev);
/*建立屬性檔案*/
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);
測試結果:
先 insmod bus.ko ,檢視發現 bus 目錄下多了 my_bus 目錄,
再檢視 my_bus 下的 devices 目錄,發現沒有檔案;
再加載 insmod device.ko ,
再檢視 my_bus 下的 devices 目錄,發現有 my_dev 連結檔案