linux-kernel - Re: [PATCH v3 2/2] Input: cros-ec-keyb - skip keyboard registration w/o cros-ec-keyb compatible

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Message-ID: <CAD=FV=XDHwOeQOFevwH9rfd=UN9OcEoOS=HeydYnNAZMUdCaBQ@mail.gmail.com>
Date:   Tue, 3 May 2022 08:09:11 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, patches@...ts.linux.dev,
        chrome-platform@...ts.linux.dev,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        "Joseph S. Barrera III" <joebar@...omium.org>
Subject: Re: [PATCH v3 2/2] Input: cros-ec-keyb - skip keyboard registration
 w/o cros-ec-keyb compatible

Hi,

On Mon, May 2, 2022 at 9:22 PM Stephen Boyd <swboyd@...omium.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 devicetrees 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. Of course, this driver won't
> probe until this patch is applied in that scenario, but that's OK. This
> last case is likely only going to be used by new devicetrees created
> after this commit.
>
> Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: <devicetree@...r.kernel.org>
> Cc: Benson Leung <bleung@...omium.org>
> Cc: Guenter Roeck <groeck@...omium.org>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Hsin-Yi Wang <hsinyi@...omium.org>
> Cc: "Joseph S. Barrera III" <joebar@...omium.org>
> Fixes: 4352e23a7ff2 ("Input: cros-ec-keyb - only register keyboard if rows/columns exist")
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/input/keyboard/cros_ec_keyb.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> index eef909e52e23..04c550aaf897 100644
> --- a/drivers/input/keyboard/cros_ec_keyb.c
> +++ b/drivers/input/keyboard/cros_ec_keyb.c
> @@ -536,14 +536,11 @@ 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;
>
> -       /*
> -        * No rows and columns? There isn't a matrix but maybe there are
> -        * switches to register in cros_ec_keyb_register_bs() because
> -        * this is a detachable device.
> -        */
> -       if (!device_property_present(dev, "keypad,num-rows") &&
> -           !device_property_present(dev, "keypad,num-cols"))
> +       /* Skip matrix registration if no keyboard */
> +       register_keyboard = device_get_match_data(dev);
> +       if (!register_keyboard)
>                 return 0;

I'm a little on the fence about the local variable. It could have been
shorter as:

/* Skip matrix registration if no keyboard */
if (!device_get_match_data(dev))

...but I guess the "register_keyboard" maybe makes it more a little
more obvious?

In any case, I'm happy either way:

Reviewed-by: Douglas Anderson <dianders@...omium.org>