linux-kernel - Re: [PATCH 05/13] thermal: rcar: Document SoC-specific bindings

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Message-ID: <CAMuHMdV1PcH-Xcn9Qkc0GoLv7vg7roXfXh1f++Sn3bycAcsKww@mail.gmail.com>
Date:	Wed, 6 Aug 2014 09:09:04 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Kuninori Morimoto <kuninori.morimoto.gx@...il.com>
Cc:	Zhang Rui <rui.zhang@...el.com>, Simon Horman <horms@...ge.net.au>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Magnus Damm <magnus.damm@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eduardo Valentin <eduardo.valentin@...com>,
	Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 05/13] thermal: rcar: Document SoC-specific bindings

Hi Morimoto-san,

On Wed, Aug 6, 2014 at 2:30 AM, Kuninori Morimoto
<kuninori.morimoto.gx@...il.com> wrote:
>> >> > >  Required properties:
>> >> > > -- compatible             : "renesas,rcar-thermal"
>> >> > > +- compatible             : "renesas,thermal-<soctype>", "renesas,rcar-thermal"
>> >> > > +                   as fallback.
>> >> > > +                   Examples with soctypes are:
>> >> > > +                     - "renesas,thermal-r8a73a4" (R-Mobile AP6)
>> >> > > +                     - "renesas,thermal-r8a7779" (R-Car H1)
>> >> > > +                     - "renesas,thermal-r8a7790" (R-Car H2)
>> >> > > +                     - "renesas,thermal-r8a7791" (R-Car M2)
>> >> > >  - reg                    : Address range of the thermal registers.
>> >> > >                     The 1st reg will be recognized as common register
>> >> > >                     if it has "interrupts".
> (snip)
>> One important thing to note in my patch description is "some of which
>> are already in use.".
>>
>> $ git grep renesas,thermal -- arch/arm/boot/ | cat
>> arch/arm/boot/dts/r8a7790.dtsi: compatible =
>> "renesas,thermal-r8a7790", "renesas,rcar-thermal";
>> arch/arm/boot/dts/r8a7791.dtsi: compatible =
>> "renesas,thermal-r8a7791", "renesas,rcar-thermal";
>> $
>>
>> So these 2 should be added to the documentation for sure.
>> Adding the 2 others, and adding them to the respective DTSes (cfr. the
>> other patches in the series) doesn't hurt, and will help if an incompatibility
>> ever arises.
>>
>> (I assume the driver works with the other DTSes that already claim to have
>> a device compatible with "renesas,rcar-thermal").
>
> I reconsidered about this.
> Actually, I'm still wondering about this approach
> because driver side doesn't have SoC specific matching table.
> Of course SoC-specific name in .compatible can be backup plan for us,
> but, we don't know it is 100% true.
> (we might have new driver for some specific SoC, like R-Car DMA driver ?)
>
> Adding to SoC specific compatible name in SoC side DTSes are no problem,
> it can be backup plan.
> but, we can't say 100% true that <driver>.txt has SoC specific name list.
> because, driver doesn't care about it today, and we don't know the future

If the SoC-specific name is used in a DTS, it must[*] be documented in the
bindings. Checkpatch.pl checks for that.

[*] The only exception is devices for which no driver exists yet. But then the
    bindings are preliminary and in limbo.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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
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