linux-kernel - Re: [PATCH 2/2] Input: cros_ec_keyb - handle x86 detachable/convertible Chromebooks

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Message-ID: <YpFSmsQ8hRM0cYG4@google.com>
Date:   Fri, 27 May 2022 15:37:14 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     linux-input@...r.kernel.org, Furquan Shaikh <furquan@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] Input: cros_ec_keyb - handle x86
 detachable/convertible Chromebooks

On Fri, May 27, 2022 at 05:35:36PM -0400, Stephen Boyd wrote:
> Quoting Dmitry Torokhov (2022-05-26 16:12:30)
> > From: Furquan Shaikh <furquan@...omium.org>
> >
> > Some detachable/convertible x86 Chromebooks use EC buttons/switches
> > interface to signal volume up/down and other buttons. This configuration is
> > signalled via presence of GOOG0007 ACPI device. The main keyboard on such
> > Chromebooks is still using the standard 8042/atkbd combo.
> >
> > Signed-off-by: Furquan Shaikh <furquan@...omium.org>
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> 
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
> 
> Two questions below.
> 
> >  drivers/input/keyboard/cros_ec_keyb.c | 21 ++++++++++++++++++---
> >  1 file changed, 18 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/input/keyboard/cros_ec_keyb.c b/drivers/input/keyboard/cros_ec_keyb.c
> > index e8338b1c5776..c14136b733a9 100644
> > --- a/drivers/input/keyboard/cros_ec_keyb.c
> > +++ b/drivers/input/keyboard/cros_ec_keyb.c
> > @@ -677,14 +678,19 @@ static const struct attribute_group cros_ec_keyb_attr_group = {
> >
> >  static int cros_ec_keyb_probe(struct platform_device *pdev)
> >  {
> > -       struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
> > +       struct cros_ec_device *ec;
> >         struct device *dev = &pdev->dev;
> >         struct cros_ec_keyb *ckdev;
> >         bool buttons_switches_only = device_get_match_data(dev);
> >         int err;
> >
> > -       if (!dev->of_node)
> > -               return -ENODEV;
> > +       /*
> > +        * If the parent ec device has not been probed yet, defer the probe of
> > +        * this keyboard/button driver until later.
> > +        */
> > +       ec = dev_get_drvdata(pdev->dev.parent);
> 
> Does cros_ec populate the child node before setting the drvdata? Or in
> ACPI designs this device is created as a child of cros_ec before the
> driver probes?

Yes, ACPI "bus" gets scanned and all device objects are created
regardless of the driver presence and whether probe has completed or
not.

Thanks.

-- 
Dmitry