原文地址：https://blog.csdn.net/weixin_45905650/article/details/121597351
文章目录
前言
本文主要来自正点原子、野火Linux教程及本人理解，若有侵权请及时联系本人删除。
正文
Device Tree Overlays："插件"设备树
传统设备树
批量管理硬件资源，机制僵化
"插件"设备树
模块化管理硬件资源，灵活定制
使用前提
- 内核配置
- CONFIG_OF_OVERLAY = y
- CONFIG_OF_CONFIGFS = y
- 挂载ConfigFS
mount x /sys/kernel/config -t configfs
案例说明
设备树：foo.dts
/ {
compatible = "corp,foo";
/* On chip peripherals */
ocp: ocp {
/* peripherals that are always instantiated */
peripheral1 { ... };
}
};
“插件”设备树：bar.dts
/dts-v1/;
/plugin/;
/ {
....
fragment@0 {
target = <&ocp>;
__overlay__ {
/* bar peripheral */
bar {
compatible = "corp,bar";
... /* various properties and child nodes */
}
};
};
};
- /dts-v1/ ：指定dts版本号
- /plugin/：允许设备树中引用未定义的节点
- target = <&xxx>：指定"插件"设备树的父节点
- target-path = “xxx”：指定"插件"设备树的父节点路径
设备树+“插件设备树”：foo.dts + bar.dts
/ {
compatible = "corp,foo";
/* shared resources */
res: res {
};
/* On chip peripherals */
ocp: ocp {
/* peripherals that are always instantiated */
peripheral1 { ... };
/* bar peripheral */
bar {
compatible = "corp,bar";
... /* various properties and child nodes */
}
}
};
编译方式
./scripts/dtc/dtc -I dts -O dtb -o xxx.dtbo arch/arm/boot/dts/xxx.dts // 编译 dts 为 dtbo
./scripts/dtc/dtc -I dtb -O dts -o xxx.dts arch/arm/boot/dts/xxx.dtbo // 反编译 dtbo 为 dts
APT下载dtc工具
sudo apt install device-tree-compiler
使用方式
内核运行状态加载(通用)
- 在/sys/kernel/config/device-tree/overlays/下创建一个新目录：
mkdir /sys/kernel/config/device-tree/overlays/xxx
- 将dtbo固件echo到path属性文件中（第一种方法）
echo xxx.dtbo >/sys/kernel/config/device-tree/overlays/xxx/path
或者将dtbo的内容cat到dtbo属性文件（第二种方法）
cat xxx.dtbo >/sys/kernel/config/device-tree/overlays/xxx/dtbo
- 节点将被创建，查看内核设备树
ls /proc/device-tree
- 删除"插件"设备树
rmdir /sys/kernel/config/device-tree/overlays/xxx
uboot加载(野火linux开发板)
修改/boot/uEnv.txt
"插件"设备树实现RGB灯驱动
设备树添加节点信息
RGB灯的相关寄存器
/*
*CCM_CCGR1 0x020C406C
*IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO04 0x020E006C
*IOMUXC_SW_PAD_CTL_PAD_GPIO1_IO04 0x020E02F8
*GPIO1_GD 0x0209C000
*GPIO1_GDIR 0x0209C004
*/
/*
*CCM_CCGR3 0x020C4074
*IOMUXC_SW_MUX_CTL_PAD_CSI_HSYNC 0x020E01E0
*IOMUXC_SW_PAD_CTL_PAD_CSI_HSYNC 0x020E046C
*GPIO4_GD 0x020A8000
*GPIO4_GDIR 0x020A8004
*/
/*
*CCM_CCGR3 0x020C4074
*IOMUXC_SW_MUX_CTL_PAD_CSI_VSYNC 0x020E01DC
*IOMUXC_SW_PAD_CTL_PAD_CSI_VSYNC 0x020E0468
*GPIO4_GD 0x020A8000
*GPIO4_GDIR 0x020A8004
*/
/*添加led节点*/
rgb_led{
#address-cells = <1>;
#size-cells = <1>;
compatible = "fire,rgb_led";
/*红灯节点*/
ranges;
rgb_led_red@0x020C406C{
reg = <0x020C406C 0x00000004
0x020E006C 0x00000004
0x020E02F8 0x00000004
0x0209C000 0x00000004
0x0209C004 0x00000004>;
status = "okay";
};
/*绿灯节点*/
rgb_led_green@0x020C4074{
reg = <0x020C4074 0x00000004
0x020E01E0 0x00000004
0x020E046C 0x00000004
0x020A8000 0x00000004
0x020A8004 0x00000004>;
status = "okay";
};
/*蓝灯节点*/
rgb_led_blue@0x020C4074{
reg = <0x020C4074 0x00000004
0x020E01DC 0x00000004
0x020E0468 0x00000004
0x020A8000 0x00000004
0x020A8004 0x00000004>;
status = "okay";
};
};
reg属性内存映射
of_iomap()函数
将reg属性值的物理地址转化为虚拟地址
void __iomem *of_iomap(struct device_node *np, int index)
参数：
- np：device_node表示的节点
- index：通常情况下reg属性包含多段，index 用于指定映射那一段，标号从0开始。
代码示例
以野火代码为例
led.dts
/dts-v1/;
/plugin/;
/ {
fragment@0 {
target-path = "/";
__overlay__ {
/* bar peripheral */
rgb_led{
#address-cells = <1>;
#size-cells = <1>;
compatible = "fire,rgb_led";
/*红灯节点*/
ranges;
rgb_led_red@0x020C406C{
reg = <0x020C406C 0x00000004
0x020E006C 0x00000004
0x020E02F8 0x00000004
0x0209C000 0x00000004
0x0209C004 0x00000004>;
status = "okay";
};
/*绿灯节点*/
rgb_led_green@0x020C4074{
reg = <0x020C4074 0x00000004
0x020E01E0 0x00000004
0x020E046C 0x00000004
0x020A8000 0x00000004
0x020A8004 0x00000004>;
status = "okay";
};
/*蓝灯节点*/
rgb_led_blue@0x020C4074{
reg = <0x020C4074 0x00000004
0x020E01DC 0x00000004
0x020E0468 0x00000004
0x020A8000 0x00000004
0x020A8004 0x00000004>;
status = "okay";
};
};
};
};
};
dts_led.c，该代码与上一篇一样
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <asm/mach/map.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_gpio.h>
#include <asm/io.h>
#include <linux/device.h>
#include <linux/platform_device.h>
/*------------------字符设备内容----------------------*/
#define DEV_NAME "rgb_led"
#define DEV_CNT (1)
/*定义 led 资源结构体，保存获取得到的节点信息以及转换后的虚拟寄存器地址*/
struct led_resource
{
struct device_node *device_node; //rgb_led_red的设备树节点
void __iomem *virtual_CCM_CCGR;
void __iomem *virtual_IOMUXC_SW_MUX_CTL_PAD;
void __iomem *virtual_IOMUXC_SW_PAD_CTL_PAD;
void __iomem *virtual_DR;
void __iomem *virtual_GDIR;
};
static dev_t led_devno; //定义字符设备的设备号
static struct cdev led_chr_dev; //定义字符设备结构体chr_dev
struct class *class_led; //保存创建的类
struct device *device; // 保存创建的设备
struct device_node *rgb_led_device_node; //rgb_led的设备树节点结构体
/*定义 R G B 三个灯的led_resource 结构体，保存获取得到的节点信息*/
struct led_resource led_red;
struct led_resource led_green;
struct led_resource led_blue;
/*字符设备操作函数集，open函数*/
static int led_chr_dev_open(struct inode *inode, struct file *filp)
{
printk("\n open form driver \n");
return 0;
}
/*字符设备操作函数集，write函数*/
static ssize_t led_chr_dev_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)
{
int ret,error;
unsigned int register_data = 0; //暂存读取得到的寄存器数据
unsigned char receive_data[10]; //用于保存接收到的数据
unsigned int write_data; //用于保存接收到的数据
if(cnt>10)
cnt =10;
error = copy_from_user(receive_data, buf, cnt);
if (error < 0)
{
return -1;
}
ret = kstrtoint(receive_data, 16, &write_data);
if (ret) {
return -1;
}
/*设置 GPIO1_04 输出电平*/
if (write_data & 0x04)
{
register_data = ioread32(led_red.virtual_DR);
register_data &= ~(0x01 << 4);
iowrite32(register_data, led_red.virtual_DR); // GPIO1_04引脚输出低电平，红灯亮
}
else
{
register_data = ioread32(led_red.virtual_DR);
register_data |= (0x01 << 4);
iowrite32(register_data, led_red.virtual_DR); // GPIO1_04引脚输出高电平，红灯灭
}
/*设置 GPIO4_20 输出电平*/
if (write_data & 0x02)
{
register_data = ioread32(led_green.virtual_DR);
register_data &= ~(0x01 << 20);
iowrite32(register_data, led_green.virtual_DR); // GPIO4_20引脚输出低电平，绿灯亮
}
else
{
register_data = ioread32(led_green.virtual_DR);
register_data |= (0x01 << 20);
iowrite32(register_data, led_green.virtual_DR); // GPIO4_20引脚输出高电平，绿灯灭
}
/*设置 GPIO4_19 输出电平*/
if (write_data & 0x01)
{
register_data = ioread32(led_blue.virtual_DR);
register_data &= ~(0x01 << 19);
iowrite32(register_data, led_blue.virtual_DR); //GPIO4_19引脚输出低电平，蓝灯亮
}
else
{
register_data = ioread32(led_blue.virtual_DR);
register_data |= (0x01 << 19);
iowrite32(register_data, led_blue.virtual_DR); //GPIO4_19引脚输出高电平，蓝灯灭
}
return cnt;
}
/*字符设备操作函数集*/
static struct file_operations led_chr_dev_fops =
{
.owner = THIS_MODULE,
.open = led_chr_dev_open,
.write = led_chr_dev_write,
};
/*----------------平台驱动函数集-----------------*/
static int led_probe(struct platform_device *pdv)
{
int ret = -1; //保存错误状态码
unsigned int register_data = 0;
printk(KERN_ALERT "\t match successed \n");
/*获取rgb_led的设备树节点*/
rgb_led_device_node = of_find_node_by_path("/rgb_led");
if (rgb_led_device_node == NULL)
{
printk(KERN_ERR "\t get rgb_led failed! \n");
return -1;
}
/*获取rgb_led节点的红灯子节点*/
led_red.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_red");
if (led_red.device_node == NULL)
{
printk(KERN_ERR "\n get rgb_led_red_device_node failed ! \n");
return -1;
}
/*获取 reg 属性并转化为虚拟地址*/
led_red.virtual_CCM_CCGR = of_iomap(led_red.device_node, 0);
led_red.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_red.device_node, 1);
led_red.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_red.device_node, 2);
led_red.virtual_DR = of_iomap(led_red.device_node, 3);
led_red.virtual_GDIR = of_iomap(led_red.device_node, 4);
/*初始化红灯*/
register_data = ioread32(led_red.virtual_CCM_CCGR);
register_data |= (0x03 << 26);
iowrite32(register_data, led_red.virtual_CCM_CCGR); //开启时钟
register_data = ioread32(led_red.virtual_IOMUXC_SW_MUX_CTL_PAD);
register_data &= ~(0xf << 0);
register_data |= (0x05 << 0);
iowrite32(register_data, led_red.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能
register_data = ioread32(led_red.virtual_IOMUXC_SW_PAD_CTL_PAD);
register_data = (0x10B0);
iowrite32(register_data, led_red.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性
register_data = ioread32(led_red.virtual_GDIR);
register_data |= (0x01 << 4);
iowrite32(register_data, led_red.virtual_GDIR); //设置GPIO1_04 为输出模式
register_data = ioread32(led_red.virtual_DR);
register_data |= (0x01 << 4);
iowrite32(register_data, led_red.virtual_DR); //设置 GPIO1_04 默认输出高电平
/*获取rgb_led节点的绿灯子节点*/
led_green.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_green");
if (led_green.device_node == NULL)
{
printk(KERN_ERR "\n get rgb_led_green_device_node failed ! \n");
return -1;
}
/*获取 reg 属性并转化为虚拟地址*/
led_green.virtual_CCM_CCGR = of_iomap(led_green.device_node, 0);
led_green.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_green.device_node, 1);
led_green.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_green.device_node, 2);
led_green.virtual_DR = of_iomap(led_green.device_node, 3);
led_green.virtual_GDIR = of_iomap(led_green.device_node, 4);
/*初始化绿灯*/
register_data = ioread32(led_green.virtual_CCM_CCGR);
register_data |= (0x03 << 12);
iowrite32(register_data, led_green.virtual_CCM_CCGR); //开启时钟
register_data = ioread32(led_green.virtual_IOMUXC_SW_MUX_CTL_PAD);
register_data &= ~(0xf << 0);
register_data |= (0x05 << 0);
iowrite32(register_data, led_green.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能
register_data = ioread32(led_green.virtual_IOMUXC_SW_PAD_CTL_PAD);
register_data = (0x10B0);
iowrite32(register_data, led_green.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性
register_data = ioread32(led_green.virtual_GDIR);
register_data |= (0x01 << 20);
iowrite32(register_data, led_green.virtual_GDIR); //设置GPIO4_IO20 为输出模式
register_data = ioread32(led_green.virtual_DR);
register_data |= (0x01 << 20);
iowrite32(register_data, led_green.virtual_DR); //设置 GPIO4_IO20 默认输出高电平
/*获取rgb_led节点的蓝灯子节点*/
led_blue.device_node = of_find_node_by_name(rgb_led_device_node,"rgb_led_blue");
if (led_blue.device_node == NULL)
{
printk(KERN_ERR "\n get rgb_led_blue_device_node failed ! \n");
return -1;
}
/*获取 reg 属性并转化为虚拟地址*/
led_blue.virtual_CCM_CCGR = of_iomap(led_blue.device_node, 0);
led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD = of_iomap(led_blue.device_node, 1);
led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD = of_iomap(led_blue.device_node, 2);
led_blue.virtual_DR = of_iomap(led_blue.device_node, 3);
led_blue.virtual_GDIR = of_iomap(led_blue.device_node, 4);
/*初始化蓝灯*/
register_data = ioread32(led_blue.virtual_CCM_CCGR);
register_data |= (0x03 << 12);
iowrite32(register_data, led_blue.virtual_CCM_CCGR); //开启时钟
register_data = ioread32(led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD);
register_data &= ~(0xf << 0);
register_data |= (0x05 << 0);
iowrite32(register_data, led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD); //设置复用功能
register_data = ioread32(led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD);
register_data = (0x10B0);
iowrite32(register_data, led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD); //设置PAD 属性
register_data = ioread32(led_blue.virtual_GDIR);
register_data |= (0x01 << 19);
iowrite32(register_data, led_blue.virtual_GDIR); //设置GPIO4_IO19 为输出模式
register_data = ioread32(led_blue.virtual_DR);
register_data |= (0x01 << 19);
iowrite32(register_data, led_blue.virtual_DR); //设置 GPIO4_IO19 默认输出高电平
/*---------------------注册 字符设备部分-----------------*/
//第一步
//采用动态分配的方式，获取设备编号，次设备号为0，
//设备名称为rgb-leds，可通过命令cat /proc/devices查看
//DEV_CNT为1，当前只申请一个设备编号
ret = alloc_chrdev_region(&led_devno, 0, DEV_CNT, DEV_NAME);
if (ret < 0)
{
printk("fail to alloc led_devno\n");
goto alloc_err;
}
//第二步
//关联字符设备结构体cdev与文件操作结构体file_operations
led_chr_dev.owner = THIS_MODULE;
cdev_init(&led_chr_dev, &led_chr_dev_fops);
//第三步
//添加设备至cdev_map散列表中
ret = cdev_add(&led_chr_dev, led_devno, DEV_CNT);
if (ret < 0)
{
printk("fail to add cdev\n");
goto add_err;
}
//第四步
/*创建类 */
class_led = class_create(THIS_MODULE, DEV_NAME);
/*创建设备*/
device = device_create(class_led, NULL, led_devno, NULL, DEV_NAME);
return 0;
add_err:
//添加设备失败时，需要注销设备号
unregister_chrdev_region(led_devno, DEV_CNT);
printk("\n error! \n");
alloc_err:
return -1;
}
static const struct of_device_id rgb_led[] = {
{.compatible = "fire,rgb_led"},
{/* sentinel */}};
/*定义平台设备结构体*/
struct platform_driver led_platform_driver = {
.probe = led_probe,
.driver = {
.name = "rgb-leds-platform",
.owner = THIS_MODULE,
.of_match_table = rgb_led,
}};
/*
*驱动初始化函数
*/
static int __init led_platform_driver_init(void)
{
int DriverState;
DriverState = platform_driver_register(&led_platform_driver);
printk(KERN_ALERT "\tDriverState is %d\n", DriverState);
return 0;
}
/*
*驱动注销函数
*/
static void __exit led_platform_driver_exit(void)
{
/*取消物理地址映射到虚拟地址*/
iounmap(led_green.virtual_CCM_CCGR);
iounmap(led_green.virtual_IOMUXC_SW_MUX_CTL_PAD);
iounmap(led_green.virtual_IOMUXC_SW_PAD_CTL_PAD);
iounmap(led_green.virtual_DR);
iounmap(led_green.virtual_GDIR);
iounmap(led_red.virtual_CCM_CCGR);
iounmap(led_red.virtual_IOMUXC_SW_MUX_CTL_PAD);
iounmap(led_red.virtual_IOMUXC_SW_PAD_CTL_PAD);
iounmap(led_red.virtual_DR);
iounmap(led_red.virtual_GDIR);
iounmap(led_blue.virtual_CCM_CCGR);
iounmap(led_blue.virtual_IOMUXC_SW_MUX_CTL_PAD);
iounmap(led_blue.virtual_IOMUXC_SW_PAD_CTL_PAD);
iounmap(led_blue.virtual_DR);
iounmap(led_blue.virtual_GDIR);
/*删除设备*/
device_destroy(class_led, led_devno); //清除设备
class_destroy(class_led); //清除类
cdev_del(&led_chr_dev); //清除设备号
unregister_chrdev_region(led_devno, DEV_CNT); //取消注册字符设备
/*注销字符设备*/
platform_driver_unregister(&led_platform_driver);
printk(KERN_ALERT "led_platform_driver exit!\n");
}
module_init(led_platform_driver_init);
module_exit(led_platform_driver_exit);
MODULE_LICENSE("GPL");
/**/
总结
将led.dts编译为rgb.dtbo插件设备树，将传统设备树和插件设备树都加载到内核中，加载完成后就使用以下命令查看设备树，此时可以在设备数中看到新增了rgb_led节点。
ls /sys/firmware/devicetree/base
或者
ls /proc/device-tree
再编译dts_led.c源文件为dto.led.ko内核模块并加载进内核。这时就有了/dev/rgb_led节点，最后向/dev/rgb_led节点写入数据就能控制rgb灯了。
sudo sh -c "ecoh '1' >/dev/rgb_led"
亮蓝灯
sudo sh -c "ecoh '2' >/dev/rgb_led"
亮绿灯
sudo sh -c "ecoh '4' >/dev/rgb_led"
亮红灯
sudo sh -c "ecoh '7' >/dev/rgb_led"
全亮