The DDI/DKI provides a group of interfaces referred to as layered device interfaces (LDI). These interfaces enable a device to be accessed from within the Solaris kernel. This capability enables developers to write applications that observe kernel device usage. For example, both the prtconf(1M) and fuser(1M) commands use LDI to enable system administrators to track aspects of device usage. The LDI is covered in more detail in Chapter 14, Layered Driver Interface (LDI).