linux-kernel - Re: [PATCH v2] platform/chrome: Don't populate lightbar device if it isn't there

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Message-ID: <CAPUE2utFmQ6YJxi4zi90i8iBSq6QCDii-HoUW-X1w1bFQ6MqEw@mail.gmail.com>
Date:   Wed, 28 Apr 2021 22:36:46 -0700
From:   Gwendal Grignou <gwendal@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Guenter Roeck <groeck@...gle.com>,
        Benson Leung <bleung@...omium.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Guenter Roeck <groeck@...omium.org>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v2] platform/chrome: Don't populate lightbar device if it
 isn't there

On Fri, Apr 9, 2021 at 6:59 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Stephen Boyd (2020-09-10 17:53:07)
> > Quoting Enric Balletbo i Serra (2020-09-10 08:49:42)
> > > On 10/9/20 16:52, Guenter Roeck wrote:
> > > > On Thu, Sep 10, 2020 at 7:32 AM Enric Balletbo i Serra
> > > > <enric.balletbo@...labora.com> wrote:
> > > >> On 10/9/20 16:18, Guenter Roeck wrote:
> > > >>> On Wed, Sep 9, 2020 at 3:42 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > > >>>> @@ -206,6 +209,17 @@ static int ec_device_probe(struct platform_device *pdev)
> > > >>>>                 }
> > > >>>>         }
> > > >>>>
> > > >>>> +       if (!strcmp(ec_platform->ec_name, CROS_EC_DEV_NAME) &&
> > > >>>> +           !cros_ec_get_lightbar_version(ec, NULL, NULL)) {
> > > >>>
> > > >>> Any idea why the lightbar code doesn't use cros_ec_check_features() ?
> > > >>> There is a definition for EC_FEATURE_LIGHTBAR, but it doesn't seem to
> > > >>> be used. It would be much more convenient if that feature check could
> > > >>> be used instead of moving the get_lightbar_version command and its
> > > >>> helper function around.
> > > >>>
> > > >>
> > > >> IIRC it was to support a very old device, the Pixel Chromebook (Link). This flag
> > > >> is not set in this device but has a lightbar, hence we had this 'weird' way to
> > > >> detect the lightbar.
> > > >>
> > > >
> > > > If that is the only reason, wouldn't it be better to use something
> > > > else (eg dmi_match) to determine if the system in question is a  Pixel
> > > > Chromebook (Link) ?
> > > >
> > > >              if (!strcmp(ec_platform->ec_name, CROS_EC_DEV_NAME) &&
> > > >                  (cros_ec_check_features(ec, EC_FEATURE_LIGHTBAR) ||
> > > >                   dmi_match(DMI_PRODUCT_NAME, "Link")) {

check_features supporting lightbar was introduced with crrev.com/c/263463
in 2015. It is present devices with lightbar like Pixel C and
backported to Pixel 2 (samus) with crrev.com/c/274047.
Remaining boards that have lightbar support and not check_features support are:
link
bolt (reference board for early samus).

Therefore, that solution is right. I will send a patch based on that
code snippet.

Gwendal.

> > > >
> > >
> > > That looks a better solution, indeed. And definetely I'd prefer use the check
> > > features way.
> > >
> > > Gwendal, can you confirm that the Pixel Chromebook (Link) is the _only_ one
> > > affected? This one is the only that comes to my mind but I might miss others.
> > >
> > > I think that Samus has this flag (I can double check) and this was discussed
> > > with you (long, long time ago :-) )
> > >
> >
> > Sounds fine by me. I'll wait for Gwendal to inform us.
>
> Anything come of this? I haven't seen any updates.