设备树中ranges属性理解

妖狐艹你老母 2022-05-22 08:45 294阅读 0赞

### 作者 ###

> 彭东林  
> pengdonglin137@163.com

### 文章来源 ###

[http://www.cnblogs.com/pengdonglin137/p/7401049.html][http_www.cnblogs.com_pengdonglin137_p_7401049.html]

### 正文 ###

##### 一、设备树 #####

*  下面是我们将要实验的设备树的例子：

/ {
        #address-cells = <1>;
        #size-cells = <1>;
    
        demo_level0 {
            compatible = "simple-bus";
            ranges = <0x0 0x3000000 0x3000>;
            #address-cells = <1>;
            #size-cells = <1>;
    
            range@0 {
                compatible = "range";
                reg = <0x100 0x200>;
                reg-names = "range0";
            };
    
            range@1 {
                compatible = "range";
                reg = <0x300 0x200>;
                reg-names = "range1";
            };
    
            range@2 {
                compatible = "range";
                reg = <0x600 0x200>;
                reg-names = "range2";
            };
    
            demo_level1 {
                compatible = "simple-bus";
                ranges = <0x0 0x1000 0x1000>;
                #address-cells = <1>;
                #size-cells = <1>;
    
                range@3 {
                    compatible = "range";
                    reg = <0x100 0x200>;
                    reg-names = "range3";
                };
    
                demo_level1-1 {
                    compatible = "simple-bus";
                    ranges = <0x0 0x300 0x500>;
                    #address-cells = <1>;
                    #size-cells = <1>;
    
                    range@4 {
                        compatible = "range";
                        reg = <0x100 0x200>;
                        reg-names = "range4";
                    };
    
                    range@5 {
                        compatible = "range";
                        reg = <0x300 0x100>;
                        reg-names = "range5";
                    };
    
                    demo_level1-1-1 {
                        compatible = "simple-bus";
                        ranges = <0x0 0x400 0x100>;
                        #address-cells = <1>;
                        #size-cells = <1>;
    
                        range@6 {
                            compatible = "range";
                            reg = <0x50 0x30>;
                            reg-names = "range6";
                        };
    
                        demo_level1-1-1-1 {
                            compatible = "simple-bus";
                            ranges = <0x0 0x20 0x20>;
                            #address-cells = <1>;
                            #size-cells = <1>;
    
                            range@7 {
                                compatible = "range";
                                reg = <0x10 0x10>;
                                reg-names = "range7";
                            };
    
                            range@8 {
                                compatible = "range";
                                reg = <0x0 0x10>;
                                reg-names = "range8";
                            };
                        };
                    };
                };
    
                range@9 {
                    compatible = "range";
                    reg = <0x800 0x50>;
                    reg-names = "range9";
                };
    
                demo_level1-2 {
                    compatible = "simple-bus";
                    ranges = <0x0 0x900 0x100>;
                    #address-cells = <1>;
                    #size-cells = <1>;
    
                    range@10 {
                        compatible = "range";
                        reg = <0x0 0x50>;
                        reg-names = "range10";
                    };
    
                    demo_level1-2-1 {
                        compatible = "simple-bus";
                        ranges;
                        #address-cells = <1>;
                        #size-cells = <1>;
    
                        range@11 {
                            compatible = "range";
                            reg = <0x50 0x30>;
                            reg-names = "range11";
                        };
                    };
                };
            };
    
            demo_level2 {
                compatible = "simple-bus";
                ranges;
                #address-cells = <1>;
                #size-cells = <1>;
    
                range@12 {
                    compatible = "range";
                    reg = <0x2000 0x1000>;
                    reg-names = "range12";
                };
            };
        }
    };

##### 二、驱动 #####

*  下面是一个简单的驱动，功能很简单，只是在probe函数中将memory资源的start和(end+1)打印出来.

demo_range.c:
    
    #include <linux/init.h>
    #include <linux/module.h>
    #include <linux/platform_device.h>
    #include <linux/of.h>
    
    static int demo_range_probe(struct platform_device *pdev)
    {
        struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    
        printk(KERN_INFO "%s start: 0x%x, end: 0x%x\n",
            res->name, res->start, res->end + 1);
    
        return 0;
    }
    
    static int demo_range_remove(struct platform_device *pdev)
    {
        return 0;
    }
    
    static const struct of_device_id demo_range_of_match[]  = {
        { .compatible = "range"},
        {},
    };
    
    static struct platform_driver demo_range_driver = {
        .driver = {
            .name = "demo_range",
            .owner = THIS_MODULE,
            .of_match_table = demo_range_of_match,
        },
        .probe = demo_range_probe,
        .remove = demo_range_remove,
    };
    module_platform_driver(demo_range_driver);
    
    MODULE_LICENSE("GPL v2");

*  在驱动中会获得memory资源，然后将start和(end+1)打印出来，之所以这里用(end+1)，仅仅是为了便于理解下面的kernel log。

##### 三、验证 #####

*  编译驱动，然后加载，可以看到下面的打印信息：

[root@vexpress mnt]# insmod demo_range.ko 
    [ 382.940402] range0 start: 0x3000100, end: 0x3000300
    [ 382.940697] range1 start: 0x3000300, end: 0x3000500
    [ 382.941448] range2 start: 0x3000600, end: 0x3000800
    [ 382.941657] range3 start: 0x3001100, end: 0x3001300
    [ 382.941855] range4 start: 0x3001400, end: 0x3001600
    [ 382.942057] range5 start: 0x3001600, end: 0x3001700
    [ 382.942262] range6 start: 0x3001750, end: 0x3001780
    [ 382.942470] range7 start: 0x3001730, end: 0x3001740
    [ 382.942684] range8 start: 0x3001720, end: 0x3001730
    [ 382.949796] range9 start: 0x3001800, end: 0x3001850
    [ 382.950023] range10 start: 0x3001900, end: 0x3001950
    [ 382.950603] range11 start: 0x3001950, end: 0x3001980
    [ 382.950805] range12 start: 0x3002000, end: 0x3003000

##### 总结： #####

*  1、ranges属性值的格式

##### 四、示意图 #####

*  对照上面的log理解下面的框图  
    ![image][]

[http_www.cnblogs.com_pengdonglin137_p_7401049.html]: http://www.cnblogs.com/pengdonglin137/p/7401049.html
[image]: /images/20220522/02b50f00bf22451d93d13b4800adb415.png