© 2014 Digi International Inc.
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ConnectCore 6 Linux BSP Reference Manual
About the ConnectCore 6 Linux BSP
This is a guide to supported devices and interfaces of the ConnectCore 6 platform in Digi
Embedded Yocto 1.6.
Linux Kernel Device Tree
Introduction
The Flattened Device Tree (FDT, or simply DT) is a data structure for describing the hardware in
a system. Rather than hard coding every detail of a device into the operating system, many
aspects of the hardware can be described in a data structure that is passed to the operating
system at boot time. The data structure itself is a simple tree of named nodes and properties.
Nodes contain properties and child nodes. Properties are simple name-value pairs. The structure
can hold any kind of data. The format is expressive and able to describe most board design
aspects including:
• The number and type of CPUs
• Base addresses and size of RAM
• Busses and bridges
• Peripheral device connections
• Interrupt controllers and IRQ line connections
Advantages
• Ship one FDT image per machine (a few kB) instead of one kernel image per machine (several
MB).
• Reduce or eliminate effort needed to write machine support code (i.e. arch/arm/mach-*).
Most board specific code changes constrained to FDT file and device drivers.
• No need to allocate a new global ARM machine id for each new board variant.
• Reduce the need to recompile the kernel. One kernel image with support for different
hardware can be shipped and be run in different variants (each one with its own FDT
describing the hardware which is really available).
• Expressive format to describe related board variants without allocating new machine numbers
or new ATAGs.
• U-Boot firmware can inspect and modify an FDT image before booting.
Formats
• *.dts: This is a Device Tree file in plain text (human readable).
• *.dtsi: This is like a DTS include file (a plain text file to be included by a DTS file).
•
*.dtb
: This is a Device Tree Blob: a binary representation of a Device Tree, once compiled
with the Device Tree compiler.
