linux-kernel - Re: [PATCH V11 3/5] kbuild: Allow .dtso format for overlay source files

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Date:   Sun, 14 Mar 2021 20:16:04 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        David Gibson <david@...son.dropbear.id.au>,
        Michal Simek <michal.simek@...inx.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Anmar Oueja <anmar.oueja@...aro.org>,
        Bill Mills <bill.mills@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V11 3/5] kbuild: Allow .dtso format for overlay source
 files

Hi VIresh,

On 3/12/21 11:11 PM, Frank Rowand wrote:
> On 3/12/21 1:13 AM, Viresh Kumar wrote:
>> On 12-03-21, 01:09, Frank Rowand wrote:
>>> I suggested having the .dtso files include the .dts file because that is a relatively
>>> small and easy change to test.  What would probably make more sense is the rename
>>> the existing overlay .dts files to be .dtso files and then for each overlay .dtso
>>> file create a new .dts file that #includes the corresponding .dtso file.  This is
>>> more work and churn, but easier to document that the .dts files are a hack that is
>>> needed so that the corresponding .dtb.S files will be generated.
>>
>> What about creating links instead then ?
>>
> 
> I don't really like the idea of using links here.
> 
> Maybe it is best to make the changes needed to allow the unittest
> overlays to be .dtso instead of .dts.
> 
> Off the top of my head:
> 
>   scripts/Makefile.lib:
>      The rule for %.dtb.S invokes cmd_dt_S_dtb, which puts the
>      overlay data in section .dtb.init.rodata, with a label
>      pointing to the beginning of the overlay __dtb_XXX_begin and
>      a label pointing to the end of the overlay __dtb_XXX_end,
>      for the overlay named XXX.  I _think_ that you could simply
>      add a corresponding rule for %.dtbo.S using a new command
>      cmd_dt_S_dtbo (the same as cmd_dt_S_dtb, except use labels
>      __dtbo_XXX_begin and __dtbo_XXX_end).

If you do the above, please put it in drivers/of/unittest-data/Makefile
instead of scripts/Makefile.lib because it is unittest.c specific and
not meant to be anywhere else in the kernel.

-Frank

> 
>   drivers/of/unittest.o:
>      would need to have the #define of OVERLAY_INFO() changed to
>      reflect the changed label names (use __dtbo_##overlayname##begin
>      and __dtb_##overlay_name##_end).
> 
>   drivers/of/unittest-data/Makefile:
>      In obj-$(CONFIG_OF_OVERLAY) change the *.dtb.o names to *.dtbo.o
> 
>      I'm not sure how the DTC_FLAGS_... += -@ differentiates between
>      .dts / .dtb and .dtso / .dtbo  That is worth looking at.
> 
> -Frank
>