本章节主要讲解代码中如何使用设备树对应的接口

视频讲解,请点解如下链接:

Linux设备树驱动开发视频-of解析dts节点的API-8



 ​​https://v.qq.com/x/page/v0378tv6esg.html​



Linux ARM设备树驱动开发视频-代码中获取节点(9)

 



​https://v.qq.com/x/page/x0378fw9wxh.html​

Linux ARM设备树驱动开发视频-代码中获取属性(10)

​https://v.qq.com/x/page/a0381pzcqeu.html​



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OF提供的函数主要集中在drivers/of/目录下,有address.c,base.c,device.c,fdt.c,irq.c,platform.c等等

1,根据deice_node结构的full_name参数,在全局链表of_allnodes中,查找合适的device_node



struct device_node *of_find_node_by_path(const char *path)



 

2,根据property结构的name参数,在指定的device node中查找合适的property



struct property *of_find_property(const struct device_node *np,const char *name,int *lenp)



3,根据compat参数与device node的compatible匹配,返回匹配度



int of_device_is_compatible(const struct device_node *device,const char *compat)



4,获得父节点的device node



struct device_node *of_get_parent(const struct device_node *node)



5,根据属性名propname,读出该属性的数组中sz个属性值给out_values



int of_property_read_u32_array(const struct device_node *np,const char *propname,,u8 *out_values, size_t sz)



6,读取该设备的第index个irq号



unsigned int irq_of_parse_and_map(struct device_node *dev, int index)

=======================================================



现在要在dts中添加如下节点,并且在代码中获取到如下信息:

test_nod@12345678{

                compatible = "test,farsight";

                reg = <0xa2345678 0x24

                         0xb3456780 0x24>;

                testprop,mytest;

                test_list_string = "red fish", "blue fish";

                interrupt-parent = <&gpx1>;  // 因为按键接到了gpx1_1

                interrupts = <1 2>;  

                // 因为按键接到了gpx1_1,如果接到gpx2_1,那么就是<2 2>

        };




#include <linux/init.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>


#define U32_DATA_LEN 4

static int is_good;
static int irqno;

irqreturn_t key_irq_handler(int irqno, void *devid)
{
printk("------------------------key pressed \n");
return IRQ_HANDLED;
}

static int __init dt_drv_init(void)
{
/*
test_nod@12345678{
compatible = "farsight,test";
reg = <0x12345678 0x24
0x87654321 0x24>;
testprop,mytest;
test_list_string = "red fish","fly fish", "blue fish";
interrupt-parent = <&gpx1>;
interrupts = <1 4>;

};
*/

// 在代码中获取节点的所有信息
//先把节点获取到
struct device_node *np = NULL;


np = of_find_node_by_path("/test_nod@12345678");
if(np){
printk("find test node ok\n");
printk("node name = %s\n", np->name);
printk("node full name = %s\n", np->full_name);

}else{
printk("find test node failed\n");

}

//获取到节点中的属性
struct property *prop = NULL;
prop = of_find_property(np, "compatible",NULL);
if(prop)
{
printk("find compatible ok\n");
printk("compatible value = %s\n", prop->value);
printk("compatible name = %s\n", prop->name);
}else{
printk("find compatible failed\n");

}

if(of_device_is_compatible(np, "farsight,test"))
{
printk("we have a compatible named farsight,test\n");
}

//读取到属性中的整数的数组

u32 regdata[U32_DATA_LEN];
int ret;

ret = of_property_read_u32_array(np, "reg", regdata, U32_DATA_LEN);
if(!ret)
{
int i;
for(i=0; i<U32_DATA_LEN; i++)
printk("----regdata[%d] = 0x%x\n", i,regdata[i]);

}else{
printk("get reg data failed\n");
}

//读取到属性中的字符串的数组
const char *pstr[3];

int i;
for(i=0; i<3; i++)
{
ret = of_property_read_string_index(np, "test_list_string", i, &pstr[i]);
if(!ret)
{
printk("----pstr[%d] = %s\n", i,pstr[i]);
}else{
printk("get pstr data failed\n");
}
}

// 属性的值为空,实际可以用于设置标志
if(of_find_property(np, "testprop,mytest", NULL))
{
is_good = 1;
printk("is_good = %d\n", is_good);
}

// 获取到中断的号码
irqno = irq_of_parse_and_map(np, 0);
printk("-----irqno = %d\n", irqno);

//验证中断号码是否有效
ret = request_irq(irqno, key_irq_handler, IRQF_TRIGGER_FALLING|IRQF_TRIGGER_RISING,
"key_irq", NULL);
if(ret)
{
printk("request_irq error\n");
return -EBUSY;
}


return 0;

}

static void __exit dt_drv_exit(void)
{
free_irq(irqno, NULL);

}




module_init(dt_drv_init);
module_exit(dt_drv_exit);
MODULE_LICENSE("GPL");