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。
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 <local地址， parent地址， size>， 表示将local地址向parent地址的转换。 比如对于#address-cells和#size-cells都为1的话，以<0x0 0x10 0x20>为例，表示将local的从0x0~(0x0 + 0x20)的地址空间映射到parent的0x10~(0x10 + 0x20) 其中，local地址的个数取决于当前含有ranges属性的节点的#address-cells属性的值，size取决于当前含有ranges属性的节点的#size-cells属性的值。 而parent地址的个数取决于当前含有ranges属性的节点的parent节点的#address-cells的值。 2、对于含有ranges属性的节点的子节点来说，其reg都是基于local地址的 3、ranges属性值为空的话，表示1:1映射 4、对于没有ranges属性的节点，代表不是memory map区域
四、示意图
对照上面的log理解下面的框图
标签：compatible,demo,cells,ranges,range,dts,reg,设备 From： https://www.cnblogs.com/god-of-death/p/17052358.html