Platform Device, Device Tree, and Open Firmware

APIs

• platform_get_resouce 和 platform_get_irq 用法

• A Tutorial on the Device Tree (Zynq) – Part IV

• 蜗窝科技 - Device Tree（三）：代码分析

從 driver 獲得硬體 resource 的 API 來觀察.

• platform

  • platform_get_resource(): memory + irq

  • platform_get_irq(): irq

• of

  • of_address_to_resource()

  • of_irq_get()

從 device tree 獲得資料的進行, 有些是 kernel 開機初始化就 access 轉成 data structure [1], 有些則是 lazy access, 在取用硬體資源前才去跟 device tree 要資料 [2].

[1] device tree in kernel init:

__init customize_machine() => of_platform_populate() => of_dev_lookup() => of_address_to_resource()

[2] lazy access:

platform_get_irq() => of_irq_get()

source code:

• driver/base/platform.c

• driver/of/*

• driver/of/platform.c

device tree format

• Free Electron - Device Tree for Dummies

• elinux - Device Tree Usage

• Documentation/devicetree/usage-model.txt

notes

• compatible property: Every node represents a device have compatible property.

  • list of strings

  • first string: the exact device, format is "<manufacturer>,<model>"

  • following strings: other devices that the device is compatible with

• node name: <name>[@<unit-address>]

• address

  • reg

  • parent’s #address-cells and #size-cells

• interrupt

  • interrupt-controller: empty property. this device receive interrupt.

  • #interrupt-cells, interrupts: like #address-cells and reg

  • interrupt-parent