| <html devsite><head> |
| <title>DTO 语法</title> |
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| <p>设备树源 (DTS) 格式是设备树的文本表示形式。设备树编译器 (DTC) 可将这种格式处理为二进制设备树，这是 Linux 内核要求的形式。</p> |
| |
| <h2 id="reference">使用引用</h2> |
| |
| <p><a href="https://github.com/pantoniou/dtc" class="external">DTC</a>（设备树编译器 + 叠加补丁程序）项目在 <a href="https://android.googlesource.com/platform/external/dtc/+/refs/heads/master/Documentation/dts-format.txt" class="external">dtc-format.txt</a> |
| 和 <a href="https://android.googlesource.com/platform/external/dtc/+/refs/heads/master/Documentation/manual.txt" class="external">manual.txt</a> 中说明了 DTS 格式。DTO 格式和规则在 <a href="https://android.googlesource.com/platform/external/dtc/+/refs/heads/master/Documentation/dt-object-internal.txt" class="external">dt-object-internal.txt</a> 中有相关说明。这些文档描述了如何使用叠加 DT 中的节点 <code>fragment@x</code> 和语法 <code>__overlay__</code> 来更新主 DT。例如：</p> |
| <pre class="prettyprint"> |
| / { |
| fragment@0 { |
| target = <&some_node>; |
| __overlay__ { |
| some_prop = "okay"; |
| ... |
| }; |
| }; |
| }; |
| </pre> |
| |
| <p>不过，Google 强烈建议您<strong>不要</strong>使用 <code>fragment@x</code> 和语法 <code>__overlay__</code>，而是使用引用语法。例如：</p> |
| <pre class="prettyprint"> |
| &some_node { |
| some_prop = "okay"; |
| ... |
| }; |
| </pre> |
| |
| <p><code>dtc</code> 会将引用语法编译成与使用语法 <code>__overlay__</code> 所生成的上述对象相同的对象。此语法不强制您对片段进行编号，让您能够轻松地读取和写入叠加 DTS。如果您的 <code>dtc</code> 不支持此语法糖，请使用 <a href="https://android.googlesource.com/platform/external/dtc" class="external">AOSP 中的 dtc |
| </a>。</p> |
| |
| <h2 id="labels">使用标签</h2> |
| <p>为了允许在编译时不编译针对节点的未定义引用，叠加 DT <code>.dts</code> 文件必须在其头文件中具有标签 <code>/plugin/</code>。例如：</p> |
| |
| <pre class="prettyprint"> |
| /dts-v1/; |
| /plugin/; |
| </pre> |
| |
| <p>在这里，您可以使用引用来定位要叠加的节点，该引用是以和符号 (＆) 作为前缀的绝对节点路径。例如，对于主 DT 中的 <code>node@0</code>：</p> |
| |
| <table> |
| <tbody><tr> |
| <th width="50%">在主 DT 中定义标签...</th> |
| <th>...然后使用标签。</th> |
| </tr> |
| |
| <tr> |
| <td> |
| <pre class="prettyprint"> |
| |
| [my_main_dt.dts] |
| |
| /dts-v1/; |
| |
| / { |
| my_node: node@0 { |
| status = "disabled"; |
| |
| my_child: child@0 { |
| value = <0xffffffff>; |
| }; |
| }; |
| }; |
| </pre> |
| </td> |
| |
| <td class="alt"> |
| <pre class="prettyprint"> |
| |
| [my_overlay_dt.dts] |
| |
| /dts-v1/; |
| /plugin/; |
| |
| &my_node { |
| status = "okay"; |
| }; |
| |
| &my_child { |
| value = <0x1>; |
| }; |
| </pre> |
| </td> |
| </tr> |
| </tbody></table> |
| |
| <h2 id="override">叠加</h2> |
| <p>如果引用目标属性存在于主 DT 中，则在 DTO 之后被叠加；否则，系统会对其进行附加。例如：</p> |
| |
| <table> |
| <tbody><tr> |
| <th width="33%">main.dts</th> |
| <th width="33%">overlay.dts</th> |
| <th>合并结果</th> |
| </tr> |
| |
| <tr> |
| <td> |
| <pre class="prettyprint"> |
| |
| [my_main_dt.dts] |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| my_node: node@0 { |
| status = "disabled"; |
| }; |
| }; |
| </pre> |
| </td> |
| |
| <td class="alt"> |
| <pre class="prettyprint"> |
| |
| [my_overlay_dt.dts] |
| |
| /dts-v1/; |
| /plugin/; |
| |
| &my_node { |
| status = "okay"; |
| }; |
| </pre> |
| </td> |
| |
| <td> |
| <pre class="prettyprint"> |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| ... |
| |
| node@0 { |
| linux,phandle = <0x1>; |
| phandle = <0x1>; |
| status = "okay"; |
| }; |
| }; |
| </pre> |
| </td> |
| </tr> |
| </tbody></table> |
| |
| <h2 id="append">附加</h2> |
| <p>如果引用目标属性不存在于主 DT 中，则在 DTO 之后被附加。例如：</p> |
| |
| <table> |
| <tbody><tr> |
| <th width="33%">main.dts</th> |
| <th width="33%">overlay.dts</th> |
| <th>合并结果</th> |
| </tr> |
| |
| <tr> |
| <td> |
| <pre class="prettyprint"> |
| |
| [my_main_dt.dts] |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| my_node: node@0 { |
| status = "okay"; |
| }; |
| }; |
| </pre> |
| </td> |
| |
| <td class="alt"> |
| <pre class="prettyprint"> |
| |
| [my_overlay_dt.dts] |
| |
| /dts-v1/; |
| /plugin/; |
| |
| &my_node { |
| new_prop = "bar"; |
| }; |
| </pre> |
| </td> |
| |
| <td> |
| <pre class="prettyprint"> |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| ... |
| |
| node@0 { |
| linux,phandle = <0x1>; |
| phandle = <0x1>; |
| status = "okay"; |
| new_prop = "bar"; |
| }; |
| }; |
| </pre> |
| </td> |
| </tr> |
| </tbody></table> |
| |
| <h2 id="child">子节点</h2> |
| <p>子节点语法示例：</p> |
| |
| <table> |
| <tbody><tr> |
| <th width="33%">main.dts</th> |
| <th width="33%">overlay.dts</th> |
| <th>合并结果</th> |
| </tr> |
| |
| <tr> |
| <td> |
| <pre class="prettyprint"> |
| |
| [my_main_dt.dts] |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| my_nodes: nodes { |
| compatible = "corp,bar"; |
| |
| node@0 { |
| status = "disabled"; |
| }; |
| }; |
| }; |
| </pre> |
| </td> |
| |
| <td class="alt"> |
| <pre class="prettyprint"> |
| |
| [my_overlay_dt.dts] |
| |
| /dts-v1/; |
| /plugin/; |
| |
| &my_nodes { |
| new_prop1 = "abc"; |
| |
| node@0 { |
| status = "okay"; |
| new_prop2 = "xyz"; |
| }; |
| }; |
| </pre> |
| </td> |
| |
| <td> |
| <pre class="prettyprint"> |
| |
| /dts-v1/; |
| |
| / { |
| compatible = "corp,foo"; |
| |
| ... |
| |
| nodes { |
| linux,phandle = <0x1>; |
| phandle = <0x1>; |
| compatible = "corp,bar"; |
| new_prop1 = "abc"; |
| |
| node@0 { |
| linux,phandle = <0x2>; |
| phandle = <0x2>; |
| status = "okay"; |
| new_prop2 = "xyz"; |
| }; |
| }; |
| }; |
| </pre> |
| </td> |
| </tr> |
| </tbody></table> |
| |
| </body></html> |
