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Subject: Re: [PATCH] of: unittest: Statically apply overlays using fdtoverlay
To:     Viresh Kumar <viresh.kumar@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        David Gibson <david@gibson.dropbear.id.au>
Cc:     Pantelis Antoniou <pantelis.antoniou@konsulko.com>,
        devicetree@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Bill Mills <bill.mills@linaro.org>,
        Anmar Oueja <anmar.oueja@linaro.org>,
        Masahiro Yamada <masahiroy@kernel.org>
References: <be5cb12a68d9ac2c35ad9dd50d6b168f7cad6837.1609996381.git.viresh.kumar@linaro.org>
 <1e42183ccafa1afba33b3e79a4e3efd3329fd133.1610095159.git.viresh.kumar@linaro.org>
 <CAL_JsqLpbSOk-OST8Oi7uyFVjekX-15713F1FbDCQWfVWgikMw@mail.gmail.com>
 <20210114050309.wokrhw4o3cjxj5uo@vireshk-i7>
 <CAL_JsqJ=jxBo2JsjNTcBnV_8OrGjUc4ZQEpdVWsfFwWb9YzyFQ@mail.gmail.com>
 <20210115054450.ab2xrohlxg7nnzpn@vireshk-i7>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <310774b2-1df6-b219-1b6d-70b8bdbb2e26@gmail.com>
Date:   Sun, 17 Jan 2021 21:54:44 -0600
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Hi Viresh,

On 1/14/21 11:44 PM, Viresh Kumar wrote:
> +David,
> 
> On 14-01-21, 09:01, Rob Herring wrote:
>> On Wed, Jan 13, 2021 at 11:03 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
>>>
>>> On 11-01-21, 09:46, Rob Herring wrote:
>>>> On Fri, Jan 8, 2021 at 2:41 AM Viresh Kumar <viresh.kumar@linaro.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 ?

I was not able to look at this until tonight.  The unittest world is somewhat
convoluted and complex.  Not at all a normal OF environment since it is directly
using both dynamic OF code and overlay apply/remove code.  Not to mention
deliberately misformed devicetree (.dts) data.  And totally hacking the loading
of FDTs in additional ways.

It is late Sunday night here (almost 10:00pm), so I am going to look at this
first thing Monday morning.

>>
>> No, because overlay_base.dts is an overlay dt.
> 
> What property of a file makes it an overlay ? Just the presence of /plugin/; ?

The "/plugin/;" in a dts file is what tells the dtc compiler to process the source
file as an overlay instead of as a base.

> 
> 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:

I'll look this over Monday morning to see what the side effects are in the
bizarre world of unittest.

> 
> 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@50000 {
>                 };
>  
>         };
> -};
> -
> 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
>