@TOC

1 dtsi中的 & 怎么理解呢?

可以把它理解引用，因为dtsi中的每个模块（驱动程序）都是用｛｝包在内的，所以当你要修改某个模块A时，可以不直接在它定义的地方修改，可以别的地方（不在同一个文件，需要#include “被访问到的.dtsi”）采用如下方式：
==&==｛
==modified: xxx==
｝;

2 举例说明

2.1 两个模块的原始定义如下：

第一个 ==simple-panel-dsi== 设备

dsi0_panel: panel@0 {
   
   
        status = "okay";
        compatible = "simple-panel-dsi";
        reg = <0>;
        num = <0>;
        id = [83 94];
        id-reg = <0x04>;
        backlight = <&backlight1>;
        pinctrl-names = "default";
        pinctrl-0 = <&lcd_rst>;
        reset-gpios = <&gpio3 RK_PC7 GPIO_ACTIVE_LOW>;
        init-delay-ms = <20>;
        reset-delay-ms = <60>;
        enable-delay-ms = <60>;
        prepare-delay-ms = <60>;
        unprepare-delay-ms = <60>;
        disable-delay-ms = <60>;
        dsi,flags = <(MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |    MIPI_DSI_MODE_LPM)>;
        dsi,format = <MIPI_DSI_FMT_RGB888>;
        dsi,lanes  = <4>;

第二个 ==regulator-fixed== 设备

vcc3v3_lcd0_n: vcc3v3-lcd0-n {
   
   
        compatible = "regulator-fixed";
        regulator-name = "vcc3v3_lcd0_n";
        regulator-boot-on;
        regulator-state-mem {
   
   
            regulator-off-in-suspend;
        };
    };

2.2 通过 ==&== 引用并修改

&DSI0_PANEL {
   
   
    POWER-SUPPLY = <&VCC3V3_LCD0_N>; // POWER-SUPPLY 接收的是另一个设备VCC3V3_LCD0_N
};
VCC3V3_LCD0_N设备我要使用到它，但是也需要修改，继续用 &
&VCC3V3_LCD0_N {
   
   
    GPIO = <&GPIO3 RK_PC6 GPIO_ACTIVE_HIGH>;
    ENABLE-ACTIVE-HIGH;
};

3 一个补丁中用到的&

在rockchip某型开发板中，只支持显示3路输出（hdmi, mipi, lvds, edp四选三），以下补丁的内容是把关掉的hdmi重新打开，从中也可以体会到 ==&==的使用技法

diff --git a/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb.dtsi b/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb.dtsi
index f200c1cda..67a349d91 100755
--- a/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb.dtsi
+++ b/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb.dtsi
@@ -228,7 +228,7 @@
     };

     edp-panel {
   
   
-        status = "okay";
+        status = "disabled";
         compatible = "simple-panel";
         backlight = <&backlight2>;
         bus-format = <MEDIA_BUS_FMT_RGB888_1X24>;
@@ -1286,7 +1286,7 @@
 };

 &hdmi {
   
   
-    status = "disabled";
+    status = "okay";
     rockchip,phy-table =
         <92812500  0x8009 0x0000 0x0270>,
         <165000000 0x800b 0x0000 0x026d>,
@@ -1297,7 +1297,7 @@
 };

 &hdmi_in_vp0 {
   
   
-    status = "disabled";
+    status = "okay";
 };

 &hdmi_in_vp1 {
   
   
@@ -1305,7 +1305,7 @@
 };

 &hdmi_sound {
   
   
-    status = "disabled";
+    status = "okay";
 };

 &i2c0 {
   
   
diff --git a/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi b/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi
index 37c013724..93206858b 100755
--- a/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi
+++ b/kernel/arch/arm64/boot/dts/rockchip/rk3568-evb1-ddr4-v10.dtsi
@@ -370,7 +370,7 @@
 };

 &route_hdmi {
   
   
-    status = "disabled";
+    status = "okay";
     connect = <&vp0_out_hdmi>;
 };

@@ -395,15 +395,15 @@
 &edp {
   
   
     force-hpd;
     //hpd-gpios = <&gpio0 RK_PC2 GPIO_ACTIVE_HIGH>;
-    status = "okay";
+    status = "disabled";
 };

 &edp_phy {
   
   
-    status = "okay";
+    status = "disabled";
 };

 &edp_in_vp0 {
   
   
-    status = "okay";
+    status = "disabled";
 };

 &edp_in_vp1 {
   
   

4 还可以用父与子的方式去理解

下图中提到的默认关闭是指 “status = "disabled"，在子dtsi中去打开它。

rk3568.dtsi理解为父dtsi, rk3568-evb.dtsi是子dtsi, rk3568-pinctrl.dtsi是专门用来书写pinctrl的dtsi

5 引发的问题

如此灵活的&运行，某个模块看起来是关的，结果却在另外一个地方打开了，如果没有仔细分析，会导致修改某个模块老是不成功，
GPIO占用怎么也消除不掉，让人抓狂。