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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Tue, 24 Aug 2021 11:20:41 +0200
Message-ID: <CAMuHMdWXXoS9mmX9VWRQyXfmsy8YROgpLZ-xB7zthEdPdM2u4A@mail.gmail.com>
Subject: Re: [PATCH 1/1] of: unittest: rename overlay source files from .dts
 to .dtso
To:     David Gibson <david@gibson.dropbear.id.au>
Cc:     Frank Rowand <frowand.list@gmail.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Rob Herring <robh@kernel.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Anmar Oueja <anmar.oueja@linaro.org>,
        Bill Mills <bill.mills@linaro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        linux-kbuild <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Pantelis Antoniou <pantelis.antoniou@konsulko.com>
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On Tue, Jun 22, 2021 at 11:44 AM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> On Sat, May 29, 2021 at 12:16 PM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
> > On Sat, May 29, 2021 at 7:16 AM David Gibson
> > <david@gibson.dropbear.id.au> wrote:
> > > On Thu, May 27, 2021 at 09:21:05AM +0200, Geert Uytterhoeven wrote:
> > > 65;6401;1c> On Thu, May 27, 2021 at 3:48 AM David Gibson
> > > > <david@gibson.dropbear.id.au> wrote:
> > > > > On Wed, May 26, 2021 at 04:21:48PM -0500, Frank Rowand wrote:
> > > > > > On 5/26/21 1:11 AM, Viresh Kumar wrote:
> > > > > > > On 22-04-21, 13:54, Frank Rowand wrote:
> > > > > > >> On 4/22/21 3:44 AM, Geert Uytterhoeven wrote:
> > > > > > >>> On Mon, Mar 29, 2021 at 9:23 PM Frank Rowand <frowand.list@gmail.com> wrote:
> > > > > > >>>> On 3/27/21 12:40 PM, Rob Herring wrote:
> > > > > > >>>>> On Wed, Mar 24, 2021 at 05:37:13PM -0500, frowand.list@gmail.com wrote:
> > > > > > >>>>>> From: Frank Rowand <frank.rowand@sony.com>
> > > > > > >>>>>>
> > > > > > >>>>>> Add Makefile rule to build .dtbo.o assembly file from overlay .dtso
> > > > > > >>>>>> source file.
> > > > > > >>>>>>
> > > > > > >>>>>> Rename unittest .dts overlay source files to use .dtso suffix.
> > > > > > >>>>>
> > > > > > >>>>> I'm pretty lukewarm on .dtso...
> > > > > > >>>>
> > > > > > >>>> I was originally also, but I'm warming up to it.
> > > > > > >>>
> > > > > > >>> What's the status of this?
> > > > > > >>
> > > > > > >> I was planning to resend on top of the upcoming -rc1.
> > > > > > >
> > > > > > > Ping.
> > > > > > >
> > > > > >
> > > > > > Thanks for the prod...
> > > > > >
> > > > > > The .dtso convention was added to the dtc compiler, then a patch was
> > > > > > accepted to revert one mention of .dtso ,though there still remains
> > > > > > two location where .dtbo is still recognized (guess_type_by_name() in
> > > > > > dtc and the help text of the fdtoverlay program).
> > > > > >
> > > > > > It seems that the general .dtso and .dtbo were not popular, so I'm
> > > > > > going to drop this patch instead of continuing to try to get it
> > > > > > accepted.
> > > > >
> > > > > AFAICT .dtbo is moderately well established, and I think it's a good
> > > > > convention, since it matters whether a blob is an overlay or base
> > > > > tree, and it's not trivial to tell which is which.
> > > >
> > > > Indeed.
> > > >
> > > > > .dtso is much more recent,
> > > >
> > > > Is it?
> > >
> > > Well, I wouldn't bet money on it, I just seem to remember encountering
> > > .dtbo for some time before .dtso was mentioned.
> > >
> > > > The oldest reference I could find is from May 2015:
> > > > "[PATCH/RFC] kbuild: Create a rule for building device tree overlay objects"
> > > > https://lore.kernel.org/linux-devicetree/1431431816-24612-1-git-send-email-geert+renesas@glider.be/
> > >
> > > Hm, I think .dtbo is even older than that, but again, I wouldn't swear
> > > to it.
> >
> > Sure. My work is based on Pantelis' work for BeagleBoard capes.
> > His code (from 2013?) used .dtbo and .dts:
> >
> >     overlay/v3.10/merge:firmware/Makefile:$(obj)/%.dtbo: $(obj)/%.dts
> > | $(objtree)/$(obj)/$$(dir %)
> >
> > So I might be the one who introduced .dtso...
> >
> > > > I have always used dtbo/dtso in my published overlays branches,
> > > > referred from https://elinux.org/R-Car/DT-Overlays, and used by
> > > > various people.
> > > >
> > > > > and I think there's much less value to it.
> > > >
> > > > IMHO the same reasoning as for dtb vs. dtbo applies to dts vs. dtso.
> > > > It matters if the resulting blob will be an overlay or base tree,
> > > > as the blob will have to be called .dtb or .dtbo.
> > > > As dtc outputs to stdout by default, the caller has to provide the
> > > > output filename, and thus needs to know.
> > > > Even if dtc would name the output file based on the presence of
> > > > "/plugin/" in the input file, the build system still needs to know
> > > > for dependency tracking.
> > >
> > > Hm, fair point.  I was thinking of the the /plugin/ tag as the
> > > distinction, whereas dtb is binary and the distinction isn't even
> > > marked in the header.  But you're right that even readable text labels
> > > inside the file don't really help make(1).  So, I retract that
> > > assertion.
> >
> > Thanks!
> >
> > > > We also do have .dts vs. .dtsi.
>
> In the mean time, we're at rc7 again?

That was v5.13-rc7. Now we're at v5.14-rc7...

Will we live with the inability to e.g. let make distinguish between
DT includes and overlays forever?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds