linux-kernel - Re: How delete node or property in overlayd dts?

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Message-ID: <d554d6aa-1301-9bf4-482b-8d8f2bb37f93@gmail.com>
Date:   Sat, 18 Aug 2018 23:12:49 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Zhang Bo <zbsdta@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: How delete node or property in overlayd dts?

On 08/18/18 03:38, Zhang Bo wrote:
> 
> 在 2018/8/18 1:47, Rob Herring 写道:
>> On Tue, Aug 14, 2018 at 7:26 PM Frank Rowand <frowand.list@...il.com> wrote:
>>> On 08/14/18 07:46, 张波 wrote:
>>>> /delete-node/ /delete-prop/ could be used in dtsi files without device
>>>> tree overlay.
>>>>
>>>> but with device tree overlay,  /delete-node/ and  /delete-prop/ are not work.
>>>> How to delete property and node in overlay dts?
>>>>
>>>> for example,
>>>> in basel.dts have following node
>>>> node1 {
>>>>      property1;
>>>>      property3;
>>>>      node2 {
>>>>          property2;
>>>>      }
>>>> }
>>>>
>>>> in overlay.dts as following
>>>>   node1 {
>>>>      /delete-property/ property1;
>>>>      /delete-node/ node2;
>>>> }
>>>>
>>>> after overlay, property1 and node2 is not deleted.
>>>>
>>> The /delete-node/ and /delete-prop/ directives are only used by the
>>> dtc compiler within a single compilation.
>>>
>>> There is nothing in the format of a devicetree blob to represent the
>>> notion of deleting a property or a node.
>>>
>>> You can not delete a property or a node in an overlay dtb.
>> Though you can add/override 'status' with 'status = "disabled";' which
>> should be treated very similar to a node not being present. I say
>> similar because it's a source of bugs for the OS to fail to pay
>> attention to status property.
> 
> there is document in https://android.googlesource.com/kernel/msm/+/android-7.0.0_r0.11/Documentation/devicetree/overlay-notes.txt> 
> In above document, remove node or property by adding - operator before node or property. but I didn't find it in released kernel source code, Is there any update plan about this problem?
> 
> {
> 
>     property-a;       /* add property-a to the target */
> 
>     -proptery-b;     /* remove property-b from the target */
> 
>     -node-b {          /* remove an exiting node-b */
> 
>         ...
> 
>     }
> 
> }
> 
> 

As far as I can tell, this version of overlay-notes.txt has never been
in the mainline kernel source.

There is no plan to support such a syntax.

-Frank