备两份内核代码。
一份专门用来用./build.sh生成镜像并烧录，设备树也在这里面改。
另一份专门用来编译内核模块，不用改里面的设备树。
cp -r /home/oct1158/Documents/Code/C/luckfox-pico/sysdrv/source/kernel /home/oct1158/Documents/Code/C/kernel_for_modules
cd /home/oct1158/Documents/Code/C/kernel_for_modules
make luckfox_rv1106_linux_defconfig ARCH=arm CROSS_COMPILE=/home/oct1158/Documents/Code/C/luckfox-pico/tools/linux/toolchain/arm-rockchip830-linux-uclibcgnueabihf/bin/arm-rockchip830-linux-uclibcgnueabihf-
make ARCH=arm CROSS_COMPILE=/home/oct1158/Documents/Code/C/luckfox-pico/tools/linux/toolchain/arm-rockchip830-linux-uclibcgnueabihf/bin/arm-rockchip830-linux-uclibcgnueabihf-

修改设备树后重新编译内核：
cd /home/oct1158/Documents/Code/C/luckfox-pico
./build.sh
烧录到板子上：
（板子拔掉USB线，按住BOOT键重新插上）
sudo ./rkflash.sh update

然后用另一份没有改设备树的内核代码重新编译驱动模块：
cd /home/oct1158/Documents/Code/C/driver_test/first
（记得把Makefile里面的内核目录KDIR改成/home/oct1158/Documents/Code/C/kernel_for_modules）
make

上传到板子上运行：
adb push test.ko /root（如果失败，那就需要先sudo adb shell一下，再exit）
sudo adb shell
cd /root
insmod test.ko

查看新增的设备树节点：
cat /sys/firmware/devicetree/base/mytest/compatible
cat /sys/firmware/devicetree/base/mytest/gpios
cat /sys/firmware/devicetree/base/mytest/name
cat /sys/firmware/devicetree/base/mytest/xxxyyy

从打印输出里面可以看到，编译好的设备树文件最终是放到boot.img镜像里面的。

Image:  resource.img (with rv1103g-luckfox-pico-mini.dtb logo.bmp logo_kernel.bmp) is ready
Image:  boot.img (FIT image with Linux kernel, FDT blob and resource) is ready

设备树文件rv1103g-luckfox-pico-mini.dts的修改内容：

/ {}里面添加

mytest {
  compatible = "mytest,myboard_20250314";
  gpios = <&gpio1 RK_PA2 GPIO_ACTIVE_HIGH>;
  xxxyyy = "https://zh.purasbar.com/post.php?t=31629";
};

内核模块test.c的代码：

#include <linux/gpio/consumer.h> // gpiod_set_value
#include <linux/module.h> // MODULE_AUTHOR, MODULE_LICENSE
#include <linux/of.h> // of_match_ptr
#include <linux/platform_device.h> // module_platform_driver

static int mytestdriver_probe(struct platform_device *pdev)
{
    const char *str;
    int ret;
    struct gpio_desc *gpio;
   
    dev_err(&pdev->dev, "probe");
    gpio = devm_gpiod_get(&pdev->dev, NULL, GPIOD_OUT_HIGH); // led on
    if (IS_ERR(gpio))
    {
        dev_err(&pdev->dev, "gpio error\n");
        return -1;
    }
    platform_set_drvdata(pdev, gpio);
   
    ret = of_property_read_string(pdev->dev.of_node, "xxxyyy", &str);
    if (ret == 0)
        dev_err(&pdev->dev, "str=%s\n", str);
    return 0;
}

static int mytestdriver_remove(struct platform_device *pdev)
{
    struct gpio_desc *gpio;
   
    dev_err(&pdev->dev, "remove");
    gpio = platform_get_drvdata(pdev);
    if (gpio != NULL)
    {
        gpiod_set_value(gpio, 0); // led off
        platform_set_drvdata(pdev, NULL);
    }
    return 0;
}

static const struct of_device_id mytestdriver_match_ids[] = {
    {.compatible = "mytest,myboard_20250314"},
    {}
};

static struct platform_driver mytestdriver = {
    .driver = {
        .name = "mytestdriver",
        .owner = THIS_MODULE,
        .of_match_table = of_match_ptr(mytestdriver_match_ids)
    },
    .probe = mytestdriver_probe,
    .remove = mytestdriver_remove
};

module_platform_driver(mytestdriver);

MODULE_AUTHOR("Oct1158");
MODULE_LICENSE("GPL");

内核模块Makefile文件：

KDIR := /home/oct1158/Documents/Code/C/kernel_for_modules
CROSS_COMPILE := /home/oct1158/Documents/Code/C/luckfox-pico/tools/linux/toolchain/arm-rockchip830-linux-uclibcgnueabihf/bin/arm-rockchip830-linux-uclibcgnueabihf-

obj-m := test.o

build:
    $(MAKE) -C $(KDIR) M=$(shell pwd) modules ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE)

clean:
    $(MAKE) -C $(KDIR) M=$(shell pwd) clean

 

[root@luckfox root]# cat /sys/firmware/devicetree/base/mytest/compatible && echo
 ""
mytest,myboard_20250314
[root@luckfox root]# cat /sys/firmware/devicetree/base/mytest/gpios && echo ""
6
[root@luckfox root]# cat /sys/firmware/devicetree/base/mytest/name && echo ""
mytest
[root@luckfox root]# cat /sys/firmware/devicetree/base/mytest/xxxyyy && echo ""
https://zh.purasbar.com/post.php?t=31629
[root@luckfox root]#

[root@luckfox root]# insmod test.ko
[ 1290.848314] mytestdriver mytest: probe
[ 1290.848491] mytestdriver mytest: str=https://zh.purasbar.com/post.php?t=31629
命令执行后，板子上的红灯常亮。

[root@luckfox root]# rmmod test
[ 1293.102352] mytestdriver mytest: remove
命令执行后，板子上的红灯熄灭。

【解决办法】编译linux内核或模块时遇到错误不显示报错信息：https://zh.purasbar.com/post.php?t=31654