设备树获取地址时碰的钉子

of_iomap()函数是从设备树获得地址并映射。但我始终获取失败，折腾了两天，终于找到原因，记录下坑位;

网上说

#address-cells = <1>;
#size-cells = <1>;

是指定其子节点的地址属性，只要子节点用reg =<>,即可。

但是，这样做并不见得奏效。后来参照了别人的设备树才发现：

最重要的是：    rangs;   对，是他，少了就不行。

原设备树：

   leds {
	#address-cells = <1>;
	#size-cells = <1>;
        compatible = "pwm-leds";
        led1 {
           	reg = <0x40000320 0x04>;
           	label = "power-led";/*HW control*/
	   	owner = "hd";
       	 };
       	led2 {
            	reg = <0x40000324 0x04>;
            	label = "sys-led";
	    	owner = "ps";
        };
       	led3 {
            	reg = <0x40000328 0x04>;
            	label = "link-led";
	    	owner = "pl";
        };
       	led4 {
            	reg = <0x4000032C 0x04>;
            	label = "act-led";
	    	owner = "ps";
        };
       	led5 {
            	reg = <0x40000330 0x04>;
            	label = "sync-led";
	    	owner = "pl";
        };
       	led6 {
            	reg = <0x40000334 0x04>;
            	label = "alarm-led";
	    	owner = "ps";
        };

   };

#address-cells = <1>;
#size-cells = <1>;

 

 

 现在正确的设备树：

   leds {
	#address-cells = <1>;
	#size-cells = <1>;
        compatible = "pwm-leds";
	ranges;
        led1 {
           	reg = <0x40000320 0x04>;
           	label = "power-led";/*HW control*/
	   	owner = "hd";
       	 };
       	led2 {
            	reg = <0x40000324 0x04>;
            	label = "sys-led";
	    	owner = "ps";
        };
       	led3 {
            	reg = <0x40000328 0x04>;
            	label = "link-led";
	    	owner = "pl";
        };
       	led4 {
            	reg = <0x4000032C 0x04>;
            	label = "act-led";
	    	owner = "ps";
        };
       	led5 {
            	reg = <0x40000330 0x04>;
            	label = "sync-led";
	    	owner = "pl";
        };
       	led6 {
            	reg = <0x40000334 0x04>;
            	label = "alarm-led";
	    	owner = "ps";
        };

   };