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From:   Stephen Boyd <swboyd@chromium.org>
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Date:   Wed, 27 Apr 2022 11:49:25 -0700
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Subject: Re: [PATCH] arm64: dts: qcom: sc7180-trogdor: Remove cros-ec keyboard
 from detachables
To:     Doug Anderson <dianders@chromium.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        LKML <linux-kernel@vger.kernel.org>, patches@lists.linux.dev,
        linux-arm-msm <linux-arm-msm@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>,
        devicetree@vger.kernel.org
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Quoting Doug Anderson (2022-04-27 08:09:59)
> Hi,
>
> On Tue, Apr 26, 2022 at 5:17 PM Doug Anderson <dianders@chromium.org> wrote:
> >
> > Hi,
> >
> > On Tue, Apr 26, 2022 at 3:57 PM Stephen Boyd <swboyd@chromium.org> wrote:
> > >
> > > Trogdor devices that have a detachable keyboard still have a
> > > non-detachable keyboard input device present because we include the
> > > cros-ec-keyboard.dtsi snippet in the top-level sc7180-trogdor.dtsi file
> > > that every variant board includes. We do this because the
> > > keyboard-controller node also provides some buttons like the power
> > > button and volume buttons. Unfortunately, this means we register a
> > > keyboard input device that doesn't do anything on boards with a
> > > detachable keyboard. Let's delete the rows/columns properties of the
> > > device node to indicate that there isn't a matrix keyboard on these
> > > boards.
> > >
> > > 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>
> > > Signed-off-by: Stephen Boyd <swboyd@chromium.org>
> > > ---
> > >  arch/arm64/boot/dts/qcom/sc7180-trogdor-coachz.dtsi   | 5 +++++
> > >  arch/arm64/boot/dts/qcom/sc7180-trogdor-homestar.dtsi | 5 +++++
> > >  2 files changed, 10 insertions(+)
> >
> > Presumably we need to do this same thing for wormdingler [1]
> >
> > [1] https://lore.kernel.org/r/20220426151204.1.Id2821de5fde55ebe928e8fc87a71c8d535edb383@changeid
> >
> > Reviewed-by: Douglas Anderson <dianders@chromium.org>
>
> Do we need to delay landing this patch for a release? I haven't tested
> myself, but from re-reading through the code it looks as if
> cros_ec_keyb_register_matrix() will return an error code if we have
> the device tree patch _without_ commit 4352e23a7ff2 ("Input:
> cros-ec-keyb - only register keyboard if rows/columns exist"). That
> will cause it to skip registering the buttons/switches, right?

Yes, if the driver patch isn't applied then we'll skip registering
switches when these properties are removed. I suppose a better way to
gracefully migrate the logic here would be to add another compatible
string. Then we could make the compatible be

	compatible = "google,cros-ec-keyb-switches", "google,cros-ec-keyb";

on detachables and the driver can skip registering the keyboard if the more
specific "google,cros-ec-keyb-switches" compatible is present. The
driver will continue to probe and we don't have to remove any
properties.

The driver patch has been accepted[1] so in theory this patch can be
applied and when the two meet up in linux-next things will work but when
bisecting down the DTS the switches won't work. Not a huge problem but
sort of annoying that the switches are busted.

[1] https://lore.kernel.org/all/Ymh1J9zQ+5EyQadE@google.com/