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From:   Dmitry Torokhov <dtor@google.com>
Date:   Thu, 4 Apr 2019 12:05:39 -0700
Message-ID: <CAE_wzQ-XuK7WOyPm6yXsmjp7z0=T92mMrfn1TVaavaLejcYVGA@mail.gmail.com>
Subject: Re: [PATCH v5 3/3] platform/chrome: Standardize Chrome OS keyboard
 backlight name
To:     Pavel Machek <pavel@ucw.cz>
Cc:     Nick Crews <ncrews@chromium.org>,
        Guenter Roeck <groeck@google.com>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Benson Leung <bleung@chromium.org>, linux-leds@vger.kernel.org,
        Jacek Anaszewski <jacek.anaszewski@gmail.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Alessandro Zummo <a.zummo@towertech.it>,
        linux-rtc@vger.kernel.org,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Duncan Laurie <dlaurie@chromium.org>,
        Simon Glass <sjg@google.com>
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On Thu, Apr 4, 2019 at 11:59 AM Pavel Machek <pavel@ucw.cz> wrote:
>
> On Thu 2019-04-04 11:55:27, Dmitry Torokhov wrote:
> > On Thu, Apr 4, 2019 at 11:41 AM Nick Crews <ncrews@chromium.org> wrote:
> > >
> > > On Thu, Apr 4, 2019 at 11:43 AM Dmitry Torokhov <dtor@google.com> wrote:
> > > >
> > > > On Thu, Apr 4, 2019 at 10:36 AM Guenter Roeck <groeck@google.com> wrote:
> > > > >
> > > > > On Thu, Apr 4, 2019 at 10:11 AM Nick Crews <ncrews@chromium.org> wrote:
> > > > > >
> > > > > > We want all backlights for the system keyboard to
> > > > > > use a common name, so the name "platform::kbd_backlight"
> > > > > > would be better than the current "chromeos::kbd_backlight"
> > > > > > name. Normally this wouldn't be worth changing, but the new
> > > > > > Wilco keyboard backlight driver uses the "platform" name.
> > > > > > We want to make it so all Chrome OS devices are consistent,
> > > > > > so we'll change the name here too.
> > > > > >
> > > > >
> > > > > Wondering - who is the "we" you are talking about ?
> > >
> > > You're right, I should have been more precise.
> > > I was referring to Pavel, Enric, and myself. Pavel had this opinion here:
> > > https://lkml.org/lkml/2019/4/4/1040. I don't know what Pavel meant by "we"
> > > in that comment, but I would guess that could mean the other LED maintainers
> > > as well? I talked with Enric 1:1 and he didn't see the problem with changing it,
> > > though perhaps he was only considering our use of the LED via powerd,
> > > and not users in general. I'm guessing Pavel's and Enric's meanings though,
> > > excuse me if I am misinterpreting.
> > >
> > > >
> > > > This also has a potential of breaking existing setups if somebody did
> > > > happen to match on entire name instead of suffix. Such changes have to
> > > > be considered very carefully; at this point I am against of doing
> > > > this.
> > >
> > > Would it make sense to keep the old name as is, and only make the new
> > > Wilco name begin with "platform:"? What would you think is best?
> >
> > Given that we do not have a single instance of platform::kbd_backlight
> > in kernel at this time I have no idea why Pavel is trying to push this
> > for Wilco driver.
>
> See the documentation in the email I sent few seconds ago. I hope it
> explains my reasoning, if not, I'll explain it.

Yes, I see the doc and I do not think I agree with it. If you look at
the LED docs you will see:

LED Device Naming
=================

Is currently of the form:

"devicename:colour:function"

It is *function* and maybe color that userspace is interested in, and
here we have proper standardization in form of "kbd_backlight". Device
name is, well, device name. It should uniquely identify the device led
is attached to, but otherwise is rarely interesting. If userspace is
really concerned what kind of keyboard backlight it is it should
investigate parent device(s) and see what they end up with.

Thanks.

--
Dmitry