Zephyr 设备树中的特殊节点-Toy模板网

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前言

在zephyr中包含一部分特殊节点，他们的功能各不相同，节点如下：

aliases
chosen
zephyr,user

aliases

aliases 是对设备树中其他节点起的别名，别名用于为节点提供较短的名称，该名称可用于设备树的其他部分以引用节点。

/{
	aliases {
		led0 = &led0;
	};

	leds {
		compatible = "gpio-leds";
		led0: led_0 {
		gpios = <&gpio1 0 0>;
		label = "LED 0";
	};
}

chosen

在Zephyr中，chosen节点是一个特殊的设备树节点，用于指定一些系统级别的属性，这些属性可以在系统启动时被引导加载程序（bootloader）或内核使用，在这个特定的设备树文件中，chosen节点支持以下属性：

zephyr,bt-c2h-uart
- Selects the UART used for host communication in the
zephyr,bt-mon-uart
- Sets UART device used for the Bluetooth monitor logging
zephyr,bt-uart
- Sets UART device used by Bluetooth
zephyr,canbus
- Sets the default CAN controller
zephyr,ccm
- Core-Coupled Memory node on some STM32 SoCs
zephyr,code-partition
- Flash partition that the Zephyr image’s text section should be linked into
zephyr,console
- Sets UART device used by console driver
zephyr,display
- Sets the default display controller
zephyr,keyboard-scan
- Sets the default keyboard scan controller
zephyr,dtcm
- Data Tightly Coupled Memory node on some Arm SoCs
zephyr,entropy
- A device which can be used as a system-wide entropy source
zephyr,flash
- A node whose reg is sometimes used to set the defaults for CONFIG_FLASH_BASE_ADDRESS and CONFIG_FLASH_SIZE
zephyr,flash-controller
- The node corresponding to the flash controller device for
  the zephyr,flash node
zephyr,gdbstub-uart
- Sets UART device used by the gdbstub subsystem
zephyr,ieee802154
- Used by the networking subsystem to set the IEEE 802.15.4 device
zephyr,ipc
- Used by the OpenAMP subsystem to specify the inter-process communication (IPC) device
zephyr,ipc_shm
- A node whose reg is used by the OpenAMP subsystem to determine the base address and size of the shared memory (SHM) usable for interprocess-communication (IPC)
zephyr,itcm
- Instruction Tightly Coupled Memory node on some Arm SoCs
zephyr,ocm
- On-chip memory node on Xilinx Zynq-7000 and ZynqMP SoCs
zephyr,osdp-uart
- Sets UART device used by OSDP subsystem
zephyr,ot-uart
- Used by the OpenThread to specify UART device for Spinel protocol
zephyr,pcie-controller
- The node corresponding to the PCIe Controller
zephyr,ppp-uart
- Sets UART device used by PPP
zephyr,settings-partition
- Fixed partition node. If defined this selects the partition used by the NVS and FCB settings backends.
zephyr,shell-uart
- Sets UART device used by serial shell backend
zephyr,sram
- A node whose reg sets the base address and size of SRAM memory
  available to the Zephyr image, used during linking
zephyr,tracing-uart
- Sets UART device used by tracing subsystem
zephyr,uart-mcumgr
- UART used for device_mgmt
zephyr,uart-pipe
- Sets UART device used by serial pipe driver
zephyr,usb-device
- USB device node. If defined and has a vbus-gpios property, these will be used by the USB subsystem to enable/disable VBUS

zephyr,user

Zephyr 的 devicetree 脚本将/zephyr,user节点作为一种特殊情况进行处理：可以将任意的属性放入其中并检索它们的值，而无需编写绑定文件。当只需要几个简单的属性时，它是一个方便的容器.

简单属性

/ {
     zephyr,user {
             boolean;
             bytes = [81 82 83];
             number = <23>;
             numbers = <1>, <2>, <3>;
             string = "text";
             strings = "a", "b", "c";
     };
};

在上面的设备树中包含了一些基本的数据类型，如果需要获取他们的值，可以通过下面的方式：

 #define ZEPHYR_USER_NODE DT_PATH(zephyr_user)

DT_PROP(ZEPHYR_USER_NODE, boolean) // 1
DT_PROP(ZEPHYR_USER_NODE, bytes)   // {0x81, 0x82, 0x83}
DT_PROP(ZEPHYR_USER_NODE, number)  // 23
DT_PROP(ZEPHYR_USER_NODE, numbers) // {1, 2, 3}
DT_PROP(ZEPHYR_USER_NODE, string)  // "text"
DT_PROP(ZEPHYR_USER_NODE, strings) // {"a", "b", "c"}

设备节点

 / {
     zephyr,user {
             handle = <&gpio0>;
             handles = <&gpio0>, <&gpio1>;
     };
};

也可以将 phandle 和 phandles 转换为设备指针：


const struct device *my_device =
     DEVICE_DT_GET(DT_PROP(ZEPHYR_USER_NODE, handle));

#define PHANDLE_TO_DEVICE(node_id, prop, idx) \
     DEVICE_DT_GET(DT_PHANDLE_BY_IDX(node_id, prop, idx)),

const struct device *my_devices[] = {
     DT_FOREACH_PROP_ELEM(ZEPHYR_USER_NODE, handles, PHANDLE_TO_DEVICE)
};

GPIOs

 #include <zephyr/dt-bindings/gpio/gpio.h>

/ {
     zephyr,user {
             signal-gpios = <&gpio0 1 GPIO_ACTIVE_HIGH>;
     };
};

除此之外，如果你需要使用GPIO，也可以直接将其添加到该节点下。文章来源地址https://www.toymoban.com/news/detail-432549.html

#include <zephyr/drivers/gpio.h>

#define ZEPHYR_USER_NODE DT_PATH(zephyr_user)

const struct gpio_dt_spec signal =
        GPIO_DT_SPEC_GET(ZEPHYR_USER_NODE, signal_gpios);

/* Configure the pin */
gpio_pin_configure_dt(&signal, GPIO_OUTPUT_INACTIVE);

/* Set the pin to its active level */
gpio_pin_set_dt(&signal, 1);