Hi Rob, Ping. There is a conflict between this and Mauro's v3 patch at: https://lore.kernel.org/r/cover.1586961793.git.mchehab+huawei@xxxxxxxxxx I pointed out the conflict to Mauro in his v2 patch, and he said he would rebase on a new -next to resolve the conflict. Unfortunately my patch was not in -next, so the conflict remains. If Mauro's patches should go in first, I can redo my patches on top of his, after his go in. -Frank On 1/27/20 6:37 PM, frowand.list@xxxxxxxxx wrote: > From: Frank Rowand <frank.rowand@xxxxxxxx> > > The overlay implementation details in the compiled (DTB) file are > now properly implemented by the dtc compiler and should no longer > be hard coded in the source file. > > Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx> > --- > > changes since v1: > - fixed typo in patch comment (implementation) > > Documentation/devicetree/overlay-notes.txt | 85 ++++++++++++------------------ > 1 file changed, 35 insertions(+), 50 deletions(-) > > diff --git a/Documentation/devicetree/overlay-notes.txt b/Documentation/devicetree/overlay-notes.txt > index 725fb8d255c1..fddc63da7dba 100644 > --- a/Documentation/devicetree/overlay-notes.txt > +++ b/Documentation/devicetree/overlay-notes.txt > @@ -19,6 +19,7 @@ Lets take an example where we have a foo board with the following base tree: > > ---- foo.dts ----------------------------------------------------------------- > /* FOO platform */ > + /dts-v1/; > / { > compatible = "corp,foo"; > > @@ -30,30 +31,25 @@ Lets take an example where we have a foo board with the following base tree: > ocp: ocp { > /* peripherals that are always instantiated */ > peripheral1 { ... }; > - } > + }; > }; > ---- foo.dts ----------------------------------------------------------------- > > -The overlay bar.dts, when loaded (and resolved as described in [1]) should > +The overlay bar.dts, > > ----- bar.dts ----------------------------------------------------------------- > -/plugin/; /* allow undefined label references and record them */ > -/ { > - .... /* various properties for loader use; i.e. part id etc. */ > - fragment@0 { > - target = <&ocp>; > - __overlay__ { > - /* bar peripheral */ > - bar { > - compatible = "corp,bar"; > - ... /* various properties and child nodes */ > - } > +---- bar.dts - overlay target location by label ------------------------------ > + /dts-v1/; > + /plugin/; > + &ocp { > + /* bar peripheral */ > + bar { > + compatible = "corp,bar"; > + ... /* various properties and child nodes */ > }; > }; > -}; > ---- bar.dts ----------------------------------------------------------------- > > -result in foo+bar.dts > +when loaded (and resolved as described in [1]) should result in foo+bar.dts > > ---- foo+bar.dts ------------------------------------------------------------- > /* FOO platform + bar peripheral */ > @@ -73,8 +69,8 @@ result in foo+bar.dts > bar { > compatible = "corp,bar"; > ... /* various properties and child nodes */ > - } > - } > + }; > + }; > }; > ---- foo+bar.dts ------------------------------------------------------------- > > @@ -82,6 +78,27 @@ As a result of the overlay, a new device node (bar) has been created > so a bar platform device will be registered and if a matching device driver > is loaded the device will be created as expected. > > +If the base DT was not compiled with the -@ option then the "&ocp" label > +will not be available to resolve the overlay node(s) to the proper location > +in the base DT. In this case, the target path can be provided. The target > +location by label syntax is preferred because the overlay can be applied to > +any base DT containing the label, no matter where the label occurs in the DT. > + > +The above bar.dts example modified to use target path syntax is: > + > +---- bar.dts - overlay target location by explicit path ---------------------- > + /dts-v1/; > + /plugin/; > + &{/ocp} { > + /* bar peripheral */ > + bar { > + compatible = "corp,bar"; > + ... /* various properties and child nodes */ > + } > + }; > +---- bar.dts ----------------------------------------------------------------- > + > + > Overlay in-kernel API > -------------------------------- > > @@ -105,35 +122,3 @@ enum of_overlay_notify_action for details. > Note that a notifier callback is not supposed to store pointers to a device > tree node or its content beyond OF_OVERLAY_POST_REMOVE corresponding to the > respective node it received. > - > -Overlay DTS Format > ------------------- > - > -The DTS of an overlay should have the following format: > - > -{ > - /* ignored properties by the overlay */ > - > - fragment@0 { /* first child node */ > - > - target=<phandle>; /* phandle target of the overlay */ > - or > - target-path="/path"; /* target path of the overlay */ > - > - __overlay__ { > - property-a; /* add property-a to the target */ > - node-a { /* add to an existing, or create a node-a */ > - ... > - }; > - }; > - } > - fragment@1 { /* second child node */ > - ... > - }; > - /* more fragments follow */ > -} > - > -Using the non-phandle based target method allows one to use a base DT which does > -not contain a __symbols__ node, i.e. it was not compiled with the -@ option. > -The __symbols__ node is only required for the target=<phandle> method, since it > -contains the information required to map from a phandle to a tree location. >
