RK3399 platform development series explanation (Introduction to the kernel) 1.28, mdev dynamically update device nodes and dynamically mount U disk

platform	Kernel version	Android version
RK3399	Linux4.4	Android7.1

1. Introduction to mdev

LinuxUsing traditional methods to create static equipment, in dev/case created a large number of nodes, regardless of these nodes corresponding hardware device is present. Linux 2.6The kernel was introduced to be executable in user space udev, allowing users to no longer need to care about the major and minor device numbers. hotplugOnly when the system detects the device's hot plug ( ) event can the /devcorresponding device node files be dynamically created and deleted. In short, udevthe main function is to create and delete device nodes in real time. If you want to be like Windowssystems, the system is able to recognize the device and mounted automatically when the device is plugged in, you can create the user space udevrules and write a script file to achieve. mdevIs actually embedded application development, udevsimplified version, its role and udevthe same, ie hot-swap event occurs or when the system starts, automatically generated files node drivers needed