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Date:   Sat, 2 Jan 2021 20:53:19 -0800
From:   Philip Chen <philipchen@...omium.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dmitry Torokhov <dtor@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Rajat Jain <rajatja@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...omium.org>,
        Rob Herring <robh+dt@...nel.org>,
        Simon Glass <sjg@...omium.org>, devicetree@...r.kernel.org,
        linux-input@...r.kernel.org
Subject: Re: [PATCH 1/3] dt-bindings: input: cros-ec-keyb: Add a new property

Hi Dmitry,

I see.
I'll update these patch sets shortly based on your suggestion.
Thanks.

On Sat, Jan 2, 2021 at 1:04 PM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
>
> On Sat, Jan 02, 2021 at 11:39:34AM -0800, Philip Chen wrote:
> > Hi Dmitry,
> >
> > Thanks for reviewing my patch over the holiday season.
> > Please check my CIL.
> >
> > On Mon, Dec 28, 2020 at 10:18 PM Dmitry Torokhov
> > <dmitry.torokhov@...il.com> wrote:
> > >
> > > Hi Philip,
> > >
> > > On Mon, Dec 21, 2020 at 05:47:57PM -0800, Philip Chen wrote:
> > > > This patch adds a new property `google,custom-keyb-top-row` to the
> > > > device tree for the custom keyboard top row design.
> > >
> > > Why don't we use the property we have for the same purpose in atkbd.c?
> > > I.e. function-row-physmap?
> > >
> > Because this property serves a different purpose than function-row-physmap.
> > `function-row-physmap` basically links the scancode to the physical
> > position in the top row.
> > `google,custom-keyb-top-row` aims at specifying the board-specific
> > keyboard top row design associated with the action codes.
> >
> > In x86 path, the board-specific keyboard top row design associated
> > with the action codes is exposed from coreboot to kernel through
> > "linux,keymap" acpi table.
> > When coreboot generates this acpi table, it asks EC to provide this
> > information, since we add the board-specific top-row-design in EC
> > codebase.
> > (E.g. https://chromium.googlesource.com/chromiumos/platform/ec/+/refs/heads/main/board/jinlon/board.c#396)
> >
> > In ARM, we don't plan to involve EC in the vivaldi support stack.
> > So `google,custom-keyb-top-row` DT property is our replacement for the
> > board-specific top-row-design in x86 EC codebase.
>
> I disagree with this decision. We already have "linux,keymap" property
> that is supposed to hold accurate keymap for the device in question,
> there should be no need to introduce yet another property to adjust the
> keymap to reflect the reality. If a device uses "non classic" ChromeOS
> top row it should not be using the default keymap from
> arch/arm/boot/dts/cros-ec-keyboard.dtsi but supply its own. You can
> consider splitting the keymap into generic lower portion and the top row
> and moving them into an .h file so they can be easily reused.
>
> >
> > > Also, instead of specifying keycodes in this array we should use
> > > combination of row and column identifying keys, like this:
> > >
> > >         function-row-physmap = <
> > >                 MATRIX_KEY(0x00, 0x02, KEY_F1),
> > >                 MATRIX_KEY(0x03, 0x02, KEY_F2),
> > >                 ...
> > >         >;
> >
> > This mapping between row/column to function keycode is fixed for all
> > Chrome OS devices.
>
> *for now* The mapping for the rest of the keyboard has also stayed
> static, but we still did not hardcode this information in the driver but
> rather used DT property to pass it into the kernel.
>
> > So we don't really need to host this information in DT.
> > Instead, I plan to hardcode this information in cros_ec_keyb.c.
> > (Please see the array "top_row_key_pos[]" in my next patch: "[2/3]
> > Input: cros_ec_keyb - Support custom top-row keys".)
> >
> > The only thing that could make the function-row-physmap file different
> > among boards is the number of top row keys.
> > But this information can be derived from the length of
> > `google,custom-keyb-top-row`.
> > So we don't need a separate DT property for it.
>
> I am sorry, but I must insist. We need to have:
>
> - accurate keymap in linux,keymap property
> - a separate property describing location of top row keys in terms of
>   rows and columns (whether we reuse MATRIX_KEY or define another macro
>   I do not really care).
>
> Thanks.
>
> --
> Dmitry

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