Re: [PATCH v2] gpio: rcar: Add r8a7793 and r8a7794 support

[Magnus Damm <magnus.damm@xxxxxxxxx>]

Hi Laurent (not Geert, sorry!),

On Mon, Dec 15, 2014 at 5:49 PM, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
> Hi Magnus,
>
> On Monday 15 December 2014 11:03:49 Magnus Damm wrote:
>> On Sat, Dec 13, 2014 at 4:17 AM, Laurent Pinchart wrote:
>> > On Friday 07 November 2014 20:54:08 Yoshihiro Kaneko wrote:
>> >> From: Hisashi Nakamura <hisashi.nakamura.ak@xxxxxxxxxxx>
>> >>
>> >> The device tree probing for R-Car M2-N (r8a7793) and R-Car E2 (r8a7794)
>> >> is added.
>> >>
>> >> Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak@xxxxxxxxxxx>
>> >> Signed-off-by: Yoshihiro Kaneko <ykaneko0929@xxxxxxxxx>
>> >> ---
>> >>
>> >> This patch is based on for-next branch of Linus Walleij's gpio tree.
>> >>
>> >> v2 [Yoshihiro Kaneko]
>> >> * As suggested by Geert Uytterhoeven
>> >>
>> >>   - clean up 4 identical copies of struct gpio_rcar_info.
>> >>
>> >>  .../devicetree/bindings/gpio/renesas,gpio-rcar.txt |  4 +++-
>> >>  drivers/gpio/gpio-rcar.c                           | 27 +++++++++-------
>> >>  2 files changed, 21 insertions(+), 10 deletions(-)
>> >>
>> >> diff --git a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
>> >> b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt index
>> >> 941a26a..38fb86f 100644
>> >> --- a/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
>> >> +++ b/Documentation/devicetree/bindings/gpio/renesas,gpio-rcar.txt
>> >>
>> >> @@ -6,7 +6,9 @@ Required Properties:
>> >>      - "renesas,gpio-r8a7778": for R8A7778 (R-Mobile M1) compatible GPIO
>> >> controller.
>> >>      - "renesas,gpio-r8a7779": for R8A7779 (R-Car H1) compatible GPIO
>> >> controller.
>> >>      - "renesas,gpio-r8a7790": for R8A7790 (R-Car H2) compatible GPIO
>> >> controller.
>> >> -    - "renesas,gpio-r8a7791": for R8A7791 (R-Car M2) compatible GPIO
>> >> controller.
>> >> +    - "renesas,gpio-r8a7791": for R8A7791 (R-Car M2-W) compatible GPIO
>> >> controller.
>> >> +    - "renesas,gpio-r8a7793": for R8A7793 (R-Car M2-N) compatible GPIO
>> >> controller.
>> >> +    - "renesas,gpio-r8a7794": for R8A7794 (R-Car E2) compatible GPIO
>> >> controller.
>> >>
>> >>      - "renesas,gpio-rcar": for generic R-Car GPIO controller.
>> >>
>> >>    - reg: Base address and length of each memory resource used by the
>> >>    GPIO
>> >>
>> >> diff --git a/drivers/gpio/gpio-rcar.c b/drivers/gpio/gpio-rcar.c
>> >> index ef71ca8..24f0343 100644
>> >> --- a/drivers/gpio/gpio-rcar.c
>> >> +++ b/drivers/gpio/gpio-rcar.c
>> >> @@ -1,6 +1,7 @@
>> >>  /*
>> >>   * Renesas R-Car GPIO Support
>> >>   *
>> >> + *  Copyright (C) 2014 Renesas Electronics Corporation
>> >>   *  Copyright (C) 2013 Magnus Damm
>> >>   *
>> >>   * This program is free software; you can redistribute it and/or modify
>> >> @@ -315,22 +316,30 @@ struct gpio_rcar_info {
>> >>       bool has_both_edge_trigger;
>> >>  };
>> >>
>> >> +static const struct gpio_rcar_info gpio_rcar_info_gen1 = {
>> >> +     .has_both_edge_trigger = false,
>> >> +};
>> >> +
>> >> +static const struct gpio_rcar_info gpio_rcar_info_gen2 = {
>> >> +     .has_both_edge_trigger = true,
>> >> +};
>> >
>> > Seriously, doesn't this call for a "renesas,gpio-rcar-gen2" compatible
>> > string ?
>>
>> Maybe, but only if we had a crystal ball and could predict that the IP
>> would be guaranteed not to change inside future Gen2 devices! =)
>
> Do we expect future Gen2 devices ? And if they happen to be incompatible we
> could call them v2.5 ;-)

Random stuff is being invented all the time. I went to an embedded
fair here in Japan a month or two ago and ran into some customer with
a board that included a Gen2-related SoC with a name I've never seen
before. I see them all the time. This particular one had super-many
camera sensors or something. Anyway, the hardware guys are not asking
for our permission before they "fork and modify". So following
well-known part numbers for DT ABI seems like a safe practice to me.

Cheers,

/ magnus
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