Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210324223713.1334666-1-frowand.list@gmail.com>
 <20210327174035.GA291160@robh.at.kernel.org> <3e6710e7-08ac-7d1b-aa69-bcd36f0d932a@gmail.com>
 <CAMuHMdXpGKMi-xv6hZQmmEw0JO=Q0WuvUzwJ2v0O28Tx5uW+sg@mail.gmail.com>
 <d1aefaae-7b12-b5fb-4b97-7230bd52c1be@gmail.com> <20210526061144.yvoaurpz75a3bsjr@vireshk-i7>
 <f651e95b-feef-5c86-edba-d6008bc80b34@gmail.com> <YK70Xsl1oXeEQpWZ@yekko>
 <CAMuHMdWdb2s08a=axC+m88gARSA3enOBnczsN59XL2F9yHXXYA@mail.gmail.com> <YLBnX4PeK51YwUJB@yekko>
In-Reply-To: <YLBnX4PeK51YwUJB@yekko>
From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Sat, 29 May 2021 12:16:58 +0200
Message-ID: <CAMuHMdXPn9FHr41xmihuuzNNNKvY-50yAwY4HyuyVo6qBn=Z1w@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>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi David,

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.

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