Re: [PATCH v5 3/3] platform/chrome: Standardize Chrome OS keyboard backlight name

From: Pavel Machek <pavel@ucw.cz>
To: Jacek Anaszewski <jacek.anaszewski@gmail.com>
Cc: Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Guenter Roeck <groeck@google.com>,
	Dmitry Torokhov <dtor@google.com>,
	Nick Crews <ncrews@chromium.org>,
	Benson Leung <bleung@chromium.org>,
	linux-leds@vger.kernel.org,
	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>
Subject: Re: [PATCH v5 3/3] platform/chrome: Standardize Chrome OS keyboard backlight name
Date: Sun, 7 Apr 2019 00:17:56 +0200	[thread overview]
Message-ID: <20190406221756.GA4472@amd> (raw)
In-Reply-To: <1b45b4e8-18b6-62d5-7d42-0feed57c2c73@gmail.com>

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Hi!

> >I am not sure about existing driver. Important thing for me is that
> >new drivers use consistent naming.
> >
> >>In cases like above:
> >>
> >>     keyboardist::kbd_backlight
> >>     tclnumpad::kbd_backlight
> >>
> >>we could do with the following:
> >>
> >>     :kbd-backlight
> >>     :numpad-backlight
> >>
> >>I used hyphens instead of underscores since we will have this convention
> >>in the LED_FUNCTION names, which is more common for Device Tree, and
> >>some of existing LED triggers.
> >
> >Existing userspace already searches for *:kbd_backlight", AFAICT, so
> >we probably want to keep the "_".
> 
> OK, but it should be an exception but not a rule.
> This "kbd-*" naming is used in input and tty subsystems which register
> keyboard triggers with this style:
> 
> ~/kernel$ git grep  ".*[\":]kbd-" -- "*.c"
> drivers/input/input-leds.c:     [LED_NUML]      = { "numlock",
> VT_TRIGGER("kbd-numlock") },

> "kbd_" naming is used only in case of backlight LEDs:
> 
> ~/kernel$ git grep  ".*[\":]kbd_" -- "*.c"
> drivers/hid/hid-asus.c: drvdata->kbd_backlight->cdev.name =
> "asus::kbd_backlight";

Yes, but userland already knows about kbd_backlight, so we really can
not change this.

> With LEDs in platform drivers is that problem that we have the name
> compiled into the kernel. Maybe to make it more flexible we could
> use kernel config to choose between new "kbd-" and legacy "kbd_"
> naming.

No, I don't think that is suitable use for config option.

> >I don't care much if we use "platform:" or no prefix at all for
> >backlight of internal keyboard, as long as it is consistent across all
> >devices.
> >
> >We certainly want to use some prefix (probably inputX:) for backlight
> >on USB keyboards.
> 
> For LEDs exposed through the input-LED bridge my get_led_device_info.sh
> script nicely reports:
> 
> associated input node: input1
> 
> It just does:
> 
> readlink input1\:\:numlock/device
> 
> which prints: "../../input1 "

Yes, that will probably work for USB keyboards. (But not for internal
keyboards on phones, etc).

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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