The EFI Driver Model is intended to simplify the design and implementation of device drivers, and
produce small executable image sizes. As a result, some complexity has been moved into bus
drivers and in a larger part into common firmware services.

A device driver is required to produce a Driver Binding Protocol on the same image handle on
which the driver was loaded. It then waits for the system firmware to connect the driver to a
controller. When that occurs, the device driver is responsible for producing a protocol on the
controller’s device handle that abstracts the I/Ooperations that the controller supports. A bus
driver performs these exact same tasks. In addition, a bus driver is also responsible for discovering
any child controllers on the bus, and creating a device handle for each child controller found.

One assumption is that the architecture of a system can be viewed as a set of one or more
processors connected to one or more core chipsets. The core chipsets are responsible for producing
one or more I/Obuses. The EFI Driver Model does not attempt to describe the processors or the
core chipsets. Instead, the EFI Driver Model describes the set of I/Obuses produced by the core
chipsets, and any children of these I/Obuses. These children can either be devices or additional
I/Obuses. This can be viewed as a tree of buses and devices with the core chipsets at the root
of that tree.