指针ptr指向结构体type中的成员member；通过指针ptr，返回结构体type的起始地址 type |----------| | | | | |----------|ptr-->| member --| |----------| | | | | |----------|/*** 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) );})--------------------------------------------------d = usb_device->dev.drivercontainer_of(d, struct usb_device_driver, drvwrap.driver) struct usb_device|----------------------------|| || ||----------------------------|| | struct device|struct device_driver *driver|--+| | -||----------------------------| - || | - || | - ||----------------------------| - | |+-------------------------------+ || struct usb_device_driver| -- |---------------------------||-- | ||-- | || -- |---------------------------|+-->|struct device_driver driver| struct usbdrv_wrap drvwrap |int for_devices| |---------------------------| | | |---------------------------|
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container_of宏，它的功能是得到包含某个结构成员的结构的指针:
其实现如下：
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#define container_of(ptr, type, member) ({ /
const typeof( ((type *)0)->member ) *__mptr = (ptr); /
(type *)( (char *)__mptr - offsetof(type,member) );})
分析可知__mptr指向的是一个type结构里typeof(((type *)0)->member)类型member成员的指针，offsetof(type,member)是这个成员在结构中的偏移，单位是字节，所以为了计算type结构的起始地址，__mptr减去它自己的偏移。