reboot系统调用的时候会调用shutdown函数

在注册platform_driver的时候，其中的shutdown函数是什么时候调用的呢？
static struct platform_driver advwdt_driver = {
.remove = advwdt_remove,
.shutdown = advwdt_shutdown,
.driver = {
.name = DRV_NAME,
},
};

其调用flow如下：reboot->kernel_restart->kernel_restart_prepare->device_shutdown
void device_shutdown(void)
{
//从device_shutdown的实现看首先调用bus->shutdown，如果bus没有shutdown，则调用dev->driver->shutdown

if (dev->bus && dev->bus->shutdown) {
if (initcall_debug)
dev_info(dev, "shutdown ");
dev->bus->shutdown(dev);
} else if (dev->driver && dev->driver->shutdown) {
if (initcall_debug)
dev_info(dev, "shutdown ");
dev->driver->shutdown(dev);
}

}
而platform_bus_type 定义如下：
struct bus_type platform_bus_type = {
.name = "platform",
.dev_groups = platform_dev_groups,
.match = platform_match,
.uevent = platform_uevent,
.pm = &platform_dev_pm_ops,
};
可以看到platform_bus_type 并没有定义shutdown函数，因此在device_shutdown 中最终会调用driver->shutdown
本例子中就是调用advwdt_shutdown

from: https://blog.csdn.net/tiantao2012/article/details/78095181?utm_source=blogxgwz1