Linux教程
Linux字符设备驱动详解六（设备树实现RGB灯驱动）
本文主要是介绍Linux字符设备驱动详解六（设备树实现RGB灯驱动），对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！
前言
请先阅读：
Linux字符设备驱动详解
Linux字符设备驱动详解二（使用设备驱动模型）
Linux字符设备驱动详解三（使用class）
Linux字符设备驱动详解四（使用自属的xbus驱动总线）
Linux字符设备驱动详解五（使用platform虚拟平台总线）
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
一、DTS设备树基本语法从上到下
背景
硬件设备中种类逐年递增，板级platform平台设备文件越来越多，这么多的设备如果都要自己写platform_device.c文件，那将需要跟每个外设的寄存器打交道，并且需要很多的platform_device.c文件
设备树简介
- DTS(device tree source)：设备树源文件，ASCII 格式
- DTC(device tree compiler)：设备树编译工具
- DTB(device tree blob)：二进制设备树
设备树使用
uboot负责加载到内存，内核解析使用
设备树源文件
ebf-buster-linux/arch/arm/boot/dts/imx6ull-seeed-npi.dts
二进制设备树
pc：ebf-buster-linux/arch/arm/boot/dts/imx6ull-seeed-npi.dtb
开发板：/boot/dtbs/4.19.71-imx-r1/imx6ull-seeed-npi.dtb
设备树编译工具
内核编译
//进行内核配置 make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- npi_v7_defconfig //编译dts make ARCH=arm -j4 CROSS_COMPILE=arm-linux-gnueabihf- dtbs
手工编译
./scripts/dtc/dtc -I dts -O dtb -o xxx.dtb arch/arm/boot/dts/xxx.dts // 编译 dts 为 dtb ./scripts/dtc/dtc -I dtb -O dts -o xxx.dts arch/arm/boot/dts/xxx.dtb // 反编译 dtb 为 dts
- -I：指定输入格式
- -O：指定输出格式
- -o：指定输出文件
设备树框架
- 从上到下
- 头文件
- 主体
- 子节点追加内容
- 从外到内
- 属性
- 其他子节点
- 属性
- 其他子节点
- …
头文件：
#include <dt-bindings/input/input.h> #include "imx6ull.dtsi"
主体：
/ {
model = "Seeed i.MX6 ULL NPi Board";
compatible = "fsl,imx6ull-14x14-evk", "fsl,imx6ull";
aliases {
pwm0 = &pwm1;
pwm1 = &pwm2;
pwm2 = &pwm3;
pwm3 = &pwm4;
};
chosen {
stdout-path = &uart1;
};
memory {
reg = <0x80000000 0x20000000>;
};
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
linux,cma {
compatible = "shared-dma-pool";
reusable;
size = <0x14000000>;
linux,cma-default;
};
};
...
};
- 多个根节点合并
- 根节点下包含多个子节点
子节点追加内容
&cpu0 {
dc-supply = <®_gpio_dvfs>;
clock-frequency = <800000000>;
};
&clks {
assigned-clocks = <&clks IMX6UL_CLK_PLL4_AUDIO_DIV>;
assigned-clock-rates = <786432000>;
};
&fec1 {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_enet1>;
phy-mode = "rmii";
phy-handle = <ðphy0>;
status = "okay";
};
节点命令
基本方法
node-name@unit-address{
属性1 = …
属性2 = …
属性3= …
子节点…
}
- node-name：指定节点的名称
- “unit-address”用于指定“单元地址”
节点标签
cpu0: cpu@0 {
compatible = "arm,cortex-a7";
device_type = "cpu";
reg = <0>;
}
- cpu0：为节点名称器一个别名
别名子节点
aliases {
二、DTS设备树基本语法从外到内
-
从上到下
- 头文件
- 主体
- 子节点追加内容
-
从外到内
- 属性
- 其他子节点
- 属性
- 其他子节点
- …
常见节点属性
compatible属性：
值类型：字符串
intc: interrupt-controller@a01000 {
compatible = "arm,cortex-a7-gic";
#interrupt-cells = <3>;
interrupt-controller;
reg = <0xa01000 0x1000>,
<0xa02000 0x100>;
};
- arm：芯片厂商
- cortex-a7-gic：模块对应的驱动名字
model属性：
值类型：字符串
model = "embedfire i.MX6 ULL NPi Board";
- 准确描述当前板子型号信息
status属性：
值类型：字符串
reg属性：
值类型：一系列《地址、长度》对
ocrams: sram@900000 {
compatible = "fsl,lpm-sram";
reg = <0x900000 0x4000>;
};
- 地址：外设寄存器组的起始地址
- 长度：外设寄存器组的字节长度
#address-cells和#size-cells属性：
值类型：u32
soc {
#address-cells = <1>;
#size-cells = <0>;
compatible = "simple-bus";
interrupt-parent = <&gpc>;
ranges;
ocrams: sram@900000 {
compatible = "fsl,lpm-sram";
reg = <0x900000>;
};
};
- #address-cells :设置子节点中reg地址的数量
- #size-cells：设置子节点中reg地址的长度的数量
linux系统中查看设备树
ls /sys/firmware/devicetree/base
或者
ls /proc/device-tree
- 以目录的形式体现设备树结构
添加子节点
test_led{
#address-cells = <1>;
#size-cells = <1>;
rgb_led_red@0x0209C000{
compatible = "fire,rgb_led_red";
reg = <0x0209C000 0x00000020>;
status = "okay";
};
};
三、获取DTS属性信息
- 查属性所在的节点
- 查节点的属性值
节点表示
struct device_node {
const char *name; //节点名
const char *type; //设备类型
phandle phandle;
const char *full_name; //完整名字
struct fwnode_handle fwnode;
struct property *properties; //属性
struct property *deadprops;
struct device_node *parent; //父节点
struct device_node *child; //子节点
struct device_node *sibling;
#if defined(CONFIG_OF_KOBJ)
struct kobject kobj;
#endif
unsigned long _flags;
void *data;
#if defined(CONFIG_SPARC)
const char *path_component_name;
unsigned int unique_id;
struct of_irq_controller *irq_trans;
#endif
};
查节点
- 路径/类型/名字/compatible
of_find_node_by_path()函数，根据路径找到节点
struct device_node *of_find_node_by_path(struct device_node *from,const char *path);
参数：
- from：开始查找的节点，NULL表示从根节点开始查找
- path：查找的节点名
返回值：
成功：device_node表示的节点
失败：NULL
of_find_node_by_type()函数，根据“device_type“属性来查找节点，不建议使用
struct device_node *of_find_node_by_type(struct device_node *from, const char *type);
of_find_node_by_name()函数，根据"name"属性来查找节点，不建议使用
struct device_node *of_find_node_by_name(struct device_node *from,const char *name);
of_find_compatible_node()函数
struct device_node *of_find_compatible_node(struct device_node *from,const char *type, const char *compat);
参数：
- from：开始查找的节点，NULL表示从根节点开始查找
- type：指定 device_type 属性值
- compat：指定 compatible 属性值
返回值：
成功：device_node表示的节点
失败：NULL
查节点的属性值
struct property {
char *name; //属性名
int length; //属性长度
void *value; //属性值
struct property *next; //下一个属性
#if defined(CONFIG_OF_DYNAMIC) || defined(CONFIG_SPARC)
unsigned long _flags;
#endif
#if defined(CONFIG_OF_PROMTREE)
unsigned int unique_id;
#endif
#if defined(CONFIG_OF_KOBJ)
struct bin_attribute attr;
#endif
};
of_find_property()函数
- 节点+属性名
查找节点中的属性
struct property *of_find_property(const struct device_node *np,const char *name,int *lenp);
参数：
- np：device_node表示的节点
- name：查找的属性名字
- lenp：属性值的字节数
返回值：
成功：property表示的属性
失败：NULL
案例：
test_property {
test_name = “hello”;
};
name：“hello”
lenp = 6
of_property_read_u32()函数，读取一个32位无符号整数
static inline int of_property_read_u32(const struct device_node *np,const char *propname,
参数：
- np：device_node表示的节点
- propname：查找的属性名字
- out_value：属性值的整数值
返回值：
成功：0
失败：负值
of_property_read_u32_array()函数，读取32位无符号整数数组
int of_property_read_u32_array(const struct device_node *np,const char *propname,u32 *out_values,size_t sz)
- np：device_node表示的节点
- name：查找的属性名字
- out_value：读取到的数组值
- sz ：要读取的数组元素数量
of_property_read_string()函数，读字符串
int of_property_read_string(struct device_node *np,const char *propname,const char **out_string)
参数：
- np：device_node表示的节点
- proname：查找的属性名字
- out_string：读取到的字符串值
返回值：
成功：0
失败：负值
代码示例
以野火设备驱动模型代码为例
get_dts_info.c
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.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 <asm/io.h>
#include <linux/of.h>
#include <linux/of_address.h>
#define DEV_NAME "get_dts_info"
#define DEV_CNT (1)
//定义字符设备的设备号
static dev_t led_devno;
//定义字符设备结构体chr_dev
static struct cdev led_chr_dev;
//创建类
struct class *led_chrdev_class;
struct device_node *led_device_node; //led的设备树节点
struct device_node *rgb_led_red_device_node; //rgb_led_red 红灯节点
struct property *rgb_led_red_property; //定义属性结构体指针
int size = 0 ;
unsigned int out_values[18]; //保存读取得到的REG 属性值
/*.open 函数*/
static int led_chr_dev_open(struct inode *inode, struct file *filp)
{
int error_status = -1;
printk("\n open form device \n");
/*获取DTS属性信息*/
led_device_node = of_find_node_by_path("/test_led");
if(led_device_node == NULL)
{
printk(KERN_ALERT "\n get led_device_node failed ! \n");
return -1;
}
/*根据 led_device_node 设备节点结构体输出节点的基本信息*/
printk(KERN_ALERT "name: %s",led_device_node->name); //输出节点名
printk(KERN_ALERT "child name: %s",led_device_node->child->name); //输出子节点的节点名
/*获取 rgb_led_red_device_node 的子节点*/
rgb_led_red_device_node = of_get_next_child(led_device_node,NULL);
if(rgb_led_red_device_node == NULL)
{
printk(KERN_ALERT "\n get rgb_led_red_device_node failed ! \n");
return -1;
}
printk(KERN_ALERT "name: %s",rgb_led_red_device_node->name); //输出节点名
printk(KERN_ALERT "parent name: %s",rgb_led_red_device_node->parent->name); //输出父节点的节点名
/*获取 rgb_led_red_device_node 节点 的"compatible" 属性 */
rgb_led_red_property = of_find_property(rgb_led_red_device_node,"compatible",&size);
if(rgb_led_red_property == NULL)
{
printk(KERN_ALERT "\n get rgb_led_red_property failed ! \n");
return -1;
}
printk(KERN_ALERT "size = : %d",size); //实际读取得到的长度
printk(KERN_ALERT "name: %s",rgb_led_red_property->name); //输出属性名
printk(KERN_ALERT "length: %d",rgb_led_red_property->length); //输出属性长度
printk(KERN_ALERT "value : %s",(char*)rgb_led_red_property->value); //属性值
/*获取 reg 地址属性*/
error_status = of_property_read_u32_array(rgb_led_red_device_node,"reg",out_values, 2);
if(error_status != 0)
{
printk(KERN_ALERT "\n get out_values failed ! \n");
return -1;
}
printk(KERN_ALERT"0x%08X ", out_values[0]);
printk(KERN_ALERT"0x%08X ", out_values[1]);
return 0;
}
/*.release 函数*/
static int led_chr_dev_release(struct inode *inode, struct file *filp)
{
printk("\nrelease\n");
return 0;
}
/*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,
.release = led_chr_dev_release,
};
/*
*驱动初始化函数
*/
static int __init led_chrdev_init(void)
{
int ret = 0;
printk("led chrdev init\n");
//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EmbedCharDev，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;
}
led_chrdev_class = class_create(THIS_MODULE, "led_chrdev");
//第二步
//关联字符设备结构体cdev与文件操作结构体file_operations
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;
}
//创建设备
device_create(led_chrdev_class, 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);
alloc_err:
return ret;
}
/*
*驱动注销函数
*/
static void __exit led_chrdev_exit(void)
{
printk("chrdev exit\n");
device_destroy(led_chrdev_class, led_devno); //清除设备
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
class_destroy(led_chrdev_class); //清除类
}
module_init(led_chrdev_init);
module_exit(led_chrdev_exit);
MODULE_LICENSE("GPL");
四、 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
以野火设备驱动模型代码为例
dts_led.c
#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
第三点get_dts_info.c仅为获取DTS属性信息演示代码。
这篇关于Linux字符设备驱动详解六（设备树实现RGB灯驱动）的文章就介绍到这儿，希望我们推荐的文章对大家有所帮助，也希望大家多多支持为之网！
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