8. 设备树 - 应用实例

      在对设备树的知识有了初步了解后，我们现在设备树下添加 test_nod 节点然后在内核驱动中对其解析。节点信息定义如下：

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>;

};

内核驱动解析：test_drv.c:

#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");