platform_set_drvdata()/platform_get_drvdata()/container_of()【转】

本文转载自:http://blog.csdn.net/angle_birds/article/details/8443695

platform_set_drvdata(struct platform_device *pdev, void *data)

platform_get_drvdata(const struct platform_device *pdev):
驱动中常用到platform_set_drvdata 和 platform_get_drvdata这两个函数,用于保存局部变量:
include/linux/platform_device.h中:
static inline void *platform_get_drvdata(const struct platform_device *pdev)
{
        return dev_get_drvdata(&pdev->dev);
}
static inline void platform_set_drvdata(struct platform_device *pdev, void *data)
{
        dev_set_drvdata(&pdev->dev, data);
}
 
static inline void
dev_set_drvdata (struct device *dev, void *data)
{
    dev->driver_data = data;
}
就是吧data赋值给dev->driver_data,pdev是平台总线设备,对于整个驱动是可见的,所以可以通过platform_get_drvdata来获取data。
 
marvell sd驱动eg:
chip是在probe函数中定义的局部变量,如果想在其他地方使用它怎么办呢? 这就需要把它保存起来。内核提供了这个方法,使用函数platform_set_drvdata()可以将chip保存成平台总线设备的私有
数据。以后再要使用它时只需调用platform_get_drvdata()就可以了。
static int sdhci_mv_probe(struct platform_device *pdev)
{
 struct sdhci_mv_chip *chip;
 struct sdhci_mv_slot *slot;
 chip = kzalloc(sizeof(struct sdhci_mv_chip), GFP_KERNEL);
 if (!chip) {
  ret = -ENOMEM;
  goto err;
 }
 chip->fixes = (sdhci_mv_get_interface(pdev) == INTERFACE_SDIO0)? &sdhci0_fixes : &sdhci1_fixes;
 if (chip->fixes)
     chip->quirks = chip->fixes->quirks;
 platform_set_drvdata(pdev, chip);
}
chip是局部变量,在驱动其他函数使用时,eg:
static int __devexit sdhci_mv_remove(struct platform_device *pdev)
{
 int i;
 struct sdhci_mv_chip *chip;
 chip = platform_get_drvdata(pdev);
 if (chip) {
  for (i = 0;i < chip->num_slots; i++)
   sdhci_mv_remove_slot(chip->slots[i]);
  platform_set_drvdata(pdev, NULL);
  kfree(chip);
 }
 return 0;
}
 
container_of(ptr, type, member)
问题:如何通过结构中的某个变量获取结构本身的指针???
container_of(ptr, type, member)宏的作用是 传入结构体类型type的域member的地址ptr,返回该结构体变量的首地址。
member是结构体类型type的成员,ptr是成员member的实例,返回ptr的入口地址;即通过结构体中一个成员的地址来得到此成员所在结构体的地址。
关于container_of见kernel.h中:
/**
* container_of - cast a member of a structure out to the containing structure
* @ptr:     the pointer to the member.
* @type:     the type of the container struct this is embedded in.
* @member:     the name of the member within the struct.
*
*/
#define container_of(ptr, type, member) ({             /
         const typeof( ((type *)0)->member ) *__mptr = (ptr);     /
         (type *)( (char *)__mptr - offsetof(type,member) );})
container_of在Linux Kernel中的应用非常广泛,它用于获得某结构中某成员的入口地址.
 
 
/* sprd keypad backlight */
struct sprd_lcd_led {
struct platform_device *pdev;
struct mutex mutex;
struct work_structwork;
spinlock_t value_lock;
enum led_brightness value;
struct led_classdev cdev;
int enabled;
int suspend;
struct early_suspend sprd_early_suspend_desc;
};
static void led_work(structwork_struct*work)
{                                       // 传入的参数是结构体类型sprd_lcd_led 的成员work的实例的地址
structsprd_lcd_led*led =container_of(work, struct sprd_lcd_led, work);
unsigned long flags;
mutex_lock(&led->mutex);
spin_lock_irqsave(&led->value_lock, flags);
if (led->value == LED_OFF || led->suspend) {
spin_unlock_irqrestore(&led->value_lock, flags);
sprd_led_disable(led);
goto out;
}
spin_unlock_irqrestore(&led->value_lock, flags);
sprd_led_enable(led);
out:
mutex_unlock(&led->mutex);
}
static void sprd_lcd_led_shutdown(structplatform_device*pdev) 
{                                          //传入的参数为platform_device 类型,所以使用platform_get_drvdata()来获取platform_device->device->driver_data

struct sprd_lcd_led*led =platform_get_drvdata(pdev);
mutex_lock(&led->mutex);
led->value = LED_OFF;
led->enabled = 1;
sprd_led_disable(led);
mutex_unlock(&led->mutex);
}
static int sprd_lcd_led_probe(structplatform_device*pdev)
{
struct sprd_lcd_led*led;//局部变量
int ret;
...............................................
led = kzalloc(sizeof(*led), GFP_KERNEL);
platform_set_drvdata(pdev, led);//局部变量保存到pdev->dev->driver_data      (platform_device->device->driver_data)
...............................................
}

转载于:https://www.cnblogs.com/zzb-Dream-90Time/p/6945028.html

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