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

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Message-ID: <CAE-0n51CVEUF4knuSAK7RWACaUF3Fmi3jmMORZb1cVFyARnHTw@mail.gmail.com>
Date:   Fri, 27 May 2022 17:35:36 -0400
From:   Stephen Boyd <swboyd@...omium.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org
Cc:     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

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?

> +       if (!ec)
> +               return -EPROBE_DEFER;
>
>         ckdev = devm_kzalloc(dev, sizeof(*ckdev), GFP_KERNEL);
>         if (!ckdev)