linux-kernel - Re: [PATCH] of: unittest: Statically apply overlays using fdtoverlay

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Date:   Fri, 15 Jan 2021 11:14:50 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rob Herring <robh+dt@...nel.org>,
        David Gibson <david@...son.dropbear.id.au>
Cc:     Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Bill Mills <bill.mills@...aro.org>,
        Anmar Oueja <anmar.oueja@...aro.org>,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: Re: [PATCH] of: unittest: Statically apply overlays using fdtoverlay

+David,

On 14-01-21, 09:01, Rob Herring wrote:
> On Wed, Jan 13, 2021 at 11:03 PM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >
> > On 11-01-21, 09:46, Rob Herring wrote:
> > > On Fri, Jan 8, 2021 at 2:41 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> > > >
> > > > Now that fdtoverlay is part of the kernel build, start using it to test
> > > > the unitest overlays we have by applying them statically.
> > >
> > > Nice idea.
> > >
> > > > The file overlay_base.dtb have symbols of its own and we need to apply
> > > > overlay.dtb to overlay_base.dtb alone first to make it work, which gives
> > > > us intermediate-overlay.dtb file.
> > >
> > > Okay? If restructuring things helps we should do that. Frank?
> >
> > Frank, do we want to do something about it ? Maybe make overlay_base.dts an dtsi
> > and include it from testcases.dts like the other ones ?
> 
> No, because overlay_base.dts is an overlay dt.

What property of a file makes it an overlay ? Just the presence of /plugin/; ?

David, we are talking about the overlay base[1] file here. The fdtoverlay tool
fails to apply it to testcases.dts file (in the same directory) because none of
its nodes have the __overlay__ label and the dtc routine overlay_merge() [2]
skips them intentionally.

> I think we need an
> empty, minimal base.dtb to apply overlay_base.dtbo to.

One way out is adding an (almost-empty) testcase-data-2 in testcases.dtb, that
will make it work.

> And then fdtoverlay needs a fix to apply overlays to the root node?

It isn't just root node I think, but any node for which the __overlay__ label
isn't there.

So this can make it all work if everyone is fine with it:

diff --git a/drivers/of/unittest-data/overlay_base.dts b/drivers/of/unittest-data/overlay_base.dts
index 99ab9d12d00b..59172c4c9e5a 100644
--- a/drivers/of/unittest-data/overlay_base.dts
+++ b/drivers/of/unittest-data/overlay_base.dts
@@ -11,8 +11,7 @@
  * dtc will create nodes "/__symbols__" and "/__local_fixups__".
  */
 
-/ {
-       testcase-data-2 {
+       &overlay_base {
                #address-cells = <1>;
                #size-cells = <1>;
 
@@ -89,5 +88,3 @@ retail_1: vending@...00 {
                };
 
        };
-};
-
diff --git a/drivers/of/unittest-data/testcases.dts b/drivers/of/unittest-data/testcases.dts
index a85b5e1c381a..539dc7d9eddc 100644
--- a/drivers/of/unittest-data/testcases.dts
+++ b/drivers/of/unittest-data/testcases.dts
@@ -11,6 +11,11 @@ node-remove {
                        };
                };
        };
+
+       overlay_base: testcase-data-2 {
+               #address-cells = <1>;
+               #size-cells = <1>;
+       };

-------------------------8<-------------------------

And then we can do this to the Makefile over my changes.

-------------------------8<-------------------------

diff --git a/drivers/of/unittest-data/Makefile b/drivers/of/unittest-data/Makefile
index 9f3eb30b78f1..8cc23311b778 100644
--- a/drivers/of/unittest-data/Makefile
+++ b/drivers/of/unittest-data/Makefile
@@ -41,7 +41,6 @@ DTC_FLAGS_testcases += -Wno-interrupts_property
 
 # Apply all overlays (except overlay_bad_* as they are not supposed to apply and
 # fail build) statically with fdtoverlay
-intermediate-overlay   := overlay.dtb
 master                 := overlay_0.dtb overlay_1.dtb overlay_2.dtb \
                           overlay_3.dtb overlay_4.dtb overlay_5.dtb \
                           overlay_6.dtb overlay_7.dtb overlay_8.dtb \
@@ -50,15 +49,12 @@ master                      := overlay_0.dtb overlay_1.dtb overlay_2.dtb \
                           overlay_gpio_01.dtb overlay_gpio_02a.dtb \
                           overlay_gpio_02b.dtb overlay_gpio_03.dtb \
                           overlay_gpio_04a.dtb overlay_gpio_04b.dtb \
-                          intermediate-overlay.dtb
+                          overlay_base.dtb overlay.dtb
 
 quiet_cmd_fdtoverlay = fdtoverlay $@
       cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $^
 
-$(obj)/intermediate-overlay.dtb: $(obj)/overlay_base.dtb $(addprefix $(obj)/,$(intermediate-overlay))
-       $(call if_changed,fdtoverlay)
-
 $(obj)/master.dtb: $(obj)/testcases.dtb $(addprefix $(obj)/,$(master))
        $(call if_changed,fdtoverlay)
 
-always-$(CONFIG_OF_OVERLAY) += intermediate-overlay.dtb master.dtb
+always-$(CONFIG_OF_OVERLAY) += master.dtb

-- 
viresh

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/of/unittest-data/overlay_base.dts
[2] https://git.kernel.org/pub/scm/utils/dtc/dtc.git/tree/libfdt/fdt_overlay.c#n628