Chapter 17. kobjects and sysfs
A significant new feature in the 2.6 Linux kernel is the addition of a unified device model. The device model provides a single mechanism for representing devices and describing their topology in the system. Such a system provides several benefits:
The initial motivation for the device model was this final point. To implement intelligent power management in the kernel, you need to be able to build a tree representing the device topology in the system. When powering down devices on a tree that grows down, the kernel must power down the lower (leaf) nodes of the tree before the higher nodes. For example, the kernel needs to turn off a USB mouse before it turns off the USB controller, and the kernel must power down the USB controller before the PCI bus. To do this accurately and efficiently for the entire system, the kernel needs a tree of devices.