Linux2.6以后的设备中，需关心总线、设备和驱动这三个实体，总线将设备和驱动绑定。系统每注册一个设备的时候，都会寻找适配的驱动，相反一样，匹配由总线完成
虚拟总线设备
struct platform_device
{
const char * name; //设备名称
int id;
struct device dev;
u32 num_resources; //设备使用各类资源的数量
struct resource * resource; //设备使用的资源
struct platform_device_id *id_entry;
};
虚拟总线驱动
struct platform_driver
{
int (*probe)(struct platform_device *);
int (*remove)(struct platform_device *);
void (*shutdown)(struct platform_device *);
int (*suspend)(struct platform_device *, pm_message_t state);
int (*suspend_late)(struct platform_device *, pm_message_t state);
int (*resume_early)(struct platform_device *);
int (*resume)(struct platform_device *);
struct pm_ext_ops *pm;
struct device_driver driver;
};
匹配通过系统为platform总线定义的一个实例中的match函数实现的
static int platform_match(struct device *dev, struct device_driver *drv)
{
struct platform_device *pdev = to_platform_device(dev);
struct platform_driver *pdrv = to_platform_driver(drv);
/*Attempt an OF style match first */
if(of_driver_match_device(dev,drv))
return 1;
/*Then try ACPI style match */
if(acpi_driver_match_device(dev,drv))
return 1;
/* match against the id table first */
if (pdrv->id_table)
return platform_match_id(pdrv->id_table, pdev) != NULL;
/* fall-back to driver name match */
return (strcmp(pdev->name, drv->name) == 0);
}
从上述可以看出，匹配有四种可能性，一是基于设备树风格的匹配，二是基于ACPI风格的匹配，三是匹配ID表（platform——device设备名是否出现在platform_driver的ID表），四是匹配platform_device设备名和驱动的名字
以下是完成的一个huaqin的platform驱动的实例，这个huaqin有一个属性节点，编译下载到手机后，adb root之后，
adb shell cat /sys/bus/platform/device/huaqin/hello ，或者 adb shell cat /sys/bus/platform/deriver/huaqin/hello屏幕上输出一个hello world 字符串
例1
#include
#include
#include
#include
#include
#include
#include
#include
struct att_dev //设备结构体
{
struct platform_device *pdev; //虚拟设备
struct kobject *kobj; //对象
};
static struct att_dev *dev = NULL; //结构体指针
static ssize_t att_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
printk("echo debug buf\n");
return count;
}
static ssize_t att_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return snprintf(buf, PAGE_SIZE, "hello world\n"); //返回一个字符串，宏是页的字节的大小
}
static DEVICE_ATTR(hello,S_IRUGO | S_IWUSR ,att_show,att_store); //定义一个宏 设置属性节点hello，参数1为节点名，参数2为权限
static int huaqin_probe(struct platform_device *pdev) //匹配platform总线成功后 在huaqin下创建一个hello节点
{
int ret;
ret = sysfs_create_file(&pdev->dev.kobj,&dev_attr_hello.attr); //这个节点位于/sys/bus/platform/device/huaqin/hello
if(ret < 0)
{
return -ENOMEM;
}
return 0;
}
static int huaqin_remove(struct platform_device *pdev)
{
return 0;
}
struct platform_driver hello_pdrv={
.probe = huaqin_probe,
.remove = huaqin_remove,
.driver = {
.name = "huaqin",
.owner = THIS_MODULE,
},
};
static int __init hello_init(void)
{
int ret;
printk(KERN_INFO "Hello World enter\n");
dev = kzalloc(sizeof(struct att_dev),GFP_KERNEL);
if(dev == NULL)
{
printk("%s get dev memory error\n",__func__);
return -ENOMEM;
}
dev->pdev = platform_device_register_simple("huaqin", -1, NULL, 0); //注册设备
ret = platform_driver_register(&hello_pdrv);
if (ret) {
printk("fail to register hello driver @ %s()\n", __func__); //注册驱动
}
return 0;
}
static void __exit hello_exit(void)
{
sysfs_remove_file(&dev->pdev->dev.kobj,&dev_attr_hello.attr);
kobject_del(dev->kobj);
platform_device_unregister(dev->pdev);
platform_driver_unregister(&hello_pdrv);
if(dev != NULL)
kfree(dev);
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("A simple Hello World Module");
例2
#include
#include
#include
#include
#include
#include
static ssize_t att_show(struct device_driver *ddd, char *buf)
{
return snprintf(buf, PAGE_SIZE, "hello world\n");
}
static ssize_t att_store(struct device *dev,struct device_attribute *attr,const char *buf, size_t count)
{
return count;
}
static DRIVER_ATTR(hello,S_IRUGO | S_IWUSR , att_show,att_store);//描述驱动属性值
static int hello_main_pdrv_probe(struct platform_device *pdev)
{
printk("@%s: hello probe done!\n", __func__);
return 0;
}
static int hello_main_pdrv_remove(struct platform_device *pdev)
{
return 0;
}
struct platform_device hello_pdev = {
.name = "huaqin",
.id = -1,
};
struct platform_driver hello_pdrv={
.probe = hello_main_pdrv_probe,
.remove = hello_main_pdrv_remove,
.driver = {
.name = "huaqin",
.owner = THIS_MODULE,
},
};
static int __init hello_init(void)
{
int ret = 0;
printk(KERN_INFO "Hello World enter\n");
ret = platform_device_register(&hello_pdev);
if (ret) {
printk("fail to register srs device @ %s()\n", __func__);
}
ret = platform_driver_register(&hello_pdrv);
if (ret) {
printk("fail to register hello driver @ %s()\n", __func__);
}
if (driver_create_file(&hello_pdrv.driver, &driver_attr_hello))
printk(KERN_NOTICE "Unable to create version attribute\n");
return 0;
}
static void __exit hello_exit(void)
{
printk(KERN_INFO "Hello World exit\n");
}
module_init(hello_init);
module_exit(hello_exit);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("A simple Hello World Module");
