linux-kernel - Re: [PATCH 1/3] HID: google: whiskers: more robust tablet mode detection

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Date:   Sun, 15 Sep 2019 20:36:34 -0700
From:   Dmitry Torokhov <dtor@...omium.org>
To:     Nicolas Boichat <drinkcat@...omium.org>
Cc:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Benson Leung <bleung@...omium.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] HID: google: whiskers: more robust tablet mode detection

On Sun, Sep 15, 2019 at 8:26 PM Nicolas Boichat <drinkcat@...omium.org> wrote:
>
> On Sat, Sep 14, 2019 at 6:03 AM Dmitry Torokhov <dtor@...omium.org> wrote:
> >
> > The USB interface may get detected before the platform/EC one, so let's
> > note the state of the base (if we receive event) and use it to correctly
> > initialize the tablet mode switch state.
> >
> > Also let's start the HID interface immediately when probing, this will
> > ensure that we correctly process "base folded" events that may be sent
> > as we initialize the base. Note that this requires us to add a release()
>
> s/release/remove/ ?

You are right.

>
> > function where we stop and close the hardware and switch the LED
> > registration away from devm interface as we need to make sure that we
> > destroy the LED instance before we stop the hardware.
> >
> > Signed-off-by: Dmitry Torokhov <dtor@...omium.org>
> > ---
> >  drivers/hid/hid-google-hammer.c | 71 ++++++++++++++++++++++++++-------
> >  1 file changed, 56 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/hid/hid-google-hammer.c b/drivers/hid/hid-google-hammer.c
> > index 84f8c127ebdc..4f64f93ddfcb 100644
> > --- a/drivers/hid/hid-google-hammer.c
> > +++ b/drivers/hid/hid-google-hammer.c
> > @@ -208,7 +209,14 @@ static int __cbas_ec_probe(struct platform_device *pdev)
> >                 return error;
> >         }
> >
> > -       input_report_switch(input, SW_TABLET_MODE, !cbas_ec.base_present);
> > +       if (!cbas_ec.base_present)
> > +               cbas_ec.base_folded = false;
>
> I'm not sure to see why this is necessary? The folded base state
> should be in bss and false anyway, and even if it was true, it would
> not change the result of the expression below (!cbas_ec.base_present
> || cbas_ec.base_folded).

To have a more accurate printout generated by the line below. The fact
that it is in bss it not relevant, as I can unbind and rebind the
driver via sysfs, so it could have stale data from the previous run.

>
> > +
> > +       dev_dbg(&pdev->dev, "%s: base: %d, folded: %d\n", __func__,
> > +               cbas_ec.base_present, cbas_ec.base_folded);
> > +
> > +       input_report_switch(input, SW_TABLET_MODE,
> > +                           !cbas_ec.base_present || cbas_ec.base_folded);
> >
> >         cbas_ec_set_input(input);
> >

Thanks,
Dmitry