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From:   Doug Anderson <dianders@chromium.org>
Date:   Mon, 2 May 2022 10:02:54 -0700
Message-ID: <CAD=FV=WAbfe9BC5QPDezz3FSEwHRFdQeZpARJYT4b9V1rNp_nA@mail.gmail.com>
Subject: Re: [PATCH v2 2/2] Input: cros-ec-keyb - skip keyboard registration
 for switches compatible
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, patches@lists.linux.dev,
        chrome-platform@lists.linux.dev,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, Benson Leung <bleung@chromium.org>,
        Guenter Roeck <groeck@chromium.org>,
        Hsin-Yi Wang <hsinyi@chromium.org>,
        "Joseph S. Barrera III" <joebar@chromium.org>
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Precedence: bulk

Hi,

On Fri, Apr 29, 2022 at 4:31 PM Stephen Boyd <swboyd@chromium.org> wrote:
>
> In commit 4352e23a7ff2 ("Input: cros-ec-keyb - only register keyboard if
> rows/columns exist") we skipped registration of the keyboard if the
> row/columns property didn't exist, but that has a slight problem for
> existing DTBs. The DTBs have the rows/columns properties, so removing
> the properties to indicate only switches exist makes this keyboard
> driver fail to probe, resulting in broken power and volume buttons. Ease
> the migration of existing DTBs by skipping keyboard registration if the
> google,cros-ec-keyb-switches compatible exists.
>
> The end result is that new DTBs can either choose to remove the matrix
> keymap properties or leave them in place and add this new compatible
> indicating the matrix keyboard properties should be ignored. Existing
> DTBs will continue to work, but they will keep registering the keyboard
> that does nothing. To fix that problem we can add this extra compatible
> to existing DTBs and the keyboard will stop being registered. Finally,
> if google,cros-ec-keyb is missing then this driver won't even attempt to
> register the matrix keyboard.
>
> Cc: Krzysztof Kozlowski <krzk@kernel.org>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: <devicetree@vger.kernel.org>
> Cc: Benson Leung <bleung@chromium.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Douglas Anderson <dianders@chromium.org>
> Cc: Hsin-Yi Wang <hsinyi@chromium.org>
> Cc: "Joseph S. Barrera III" <joebar@chromium.org>
> Fixes: 4352e23a7ff2 ("Input: cros-ec-keyb - only register keyboard if rows/columns exist")
> Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> ---
>  drivers/input/keyboard/cros_ec_keyb.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> index eef909e52e23..1bbe2987bf52 100644
> --- a/drivers/input/keyboard/cros_ec_keyb.c
> +++ b/drivers/input/keyboard/cros_ec_keyb.c
> @@ -536,6 +536,12 @@ static int cros_ec_keyb_register_matrix(struct cros_ec_keyb *ckdev)
>         u32 *physmap;
>         u32 key_pos;
>         unsigned int row, col, scancode, n_physmap;
> +       bool register_keyboard;
> +
> +       /* Skip matrix registration if no keyboard */
> +       register_keyboard = device_get_match_data(dev);
> +       if (!register_keyboard)
> +               return 0;
>
>         /*
>          * No rows and columns? There isn't a matrix but maybe there are

As per my comments in patch #1, I wonder if it makes sense to delete
the "No rows and columns?" logic and settle on the compatible as the
one true way to specify this.

-Doug