Embedding_FreeBSD [FreeBSD WIKI]

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===== Embedding FreeBSD =====

==== Device description ====

Definition: a flexible/generic mechanism for describing a single device (aka package).

  * A device description has some type (could be class with sub-classes), used to match drivers to devices (akin to PCI).
  * Contains a device's resources (I/O, interrupt, etc)
  * Contains attributes
  * Can contain "hints" to the OS for purposes of wiring devices down to drivers and unit numbers.

==== Device tree ====

Definition: a collection of device descriptions organized in a hierarchical structure.

  * Can be partial; sub-trees that can be mapped/rooted at runtime.

==== Implementation ====

  * Textual representation. At first, the kernel will parse and translate to make it easier to 1) compile-in, 2) load as module, and 3) manually enter while booting.
  * Bus driver that takes a device tree, parses it and creates the appropriate newbus hierarchy, followed by the standard probe and attach.

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