linux-kernel - Re: [PATCH] leds: ariel: Add driver for status LEDs on Dell Wyse 3020

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Date:   Wed, 18 Mar 2020 10:43:14 +0100
From:   Lubomir Rintel <lkundrak@...sk>
To:     Pavel Machek <pavel@....cz>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>, linux-kernel@...r.kernel.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH] leds: ariel: Add driver for status LEDs on Dell Wyse 3020

On Sun, Mar 15, 2020 at 09:42:30AM +0100, Pavel Machek wrote:
> Hi!
> 
> > This adds support for controlling the LEDs attached to the Embedded
> > Controller on a Dell Wyse 3020 "Ariel" board.
> > 
> > Signed-off-by: Lubomir Rintel <lkundrak@...sk>
> 
> Does not look bad.
> 
> > +static int ariel_led_probe(struct platform_device *pdev)
> > +{
> > +	struct device *dev = &pdev->dev;
> > +	struct ariel_led *leds;
> > +	struct regmap *ec_ram;
> > +	int ret;
> > +
> > +	leds = devm_kcalloc(dev, 3, sizeof(*leds), GFP_KERNEL);
> > +	if (!leds)
> > +		return -ENOMEM;
> > +
> > +	ec_ram = dev_get_regmap(dev->parent, "ec_ram");
> > +	if (!ec_ram)
> > +		return -ENODEV;
> > +
> > +	leds[0].ec_ram = ec_ram;
> > +	leds[0].ec_index = EC_BLUE_LED;
> > +	leds[0].led_cdev.name = "ariel:blue:power",
> > +	leds[0].led_cdev.brightness_get = ariel_led_get;
> > +	leds[0].led_cdev.brightness_set = ariel_led_set;
> > +	leds[0].led_cdev.blink_set = ariel_blink_set;
> > +	leds[0].led_cdev.default_trigger = "default-on";
> 
> Move common settings to a loop?
> 
> Definitely delete "ariel:" prefix.
> 
> > +	leds[1].led_cdev.name = "ariel:amber:status",
> > +	leds[2].led_cdev.name = "ariel:green:status",
> 
> Do the LEDs have some label, or some kind of common function? Calling
> it ":status" is not too useful...

No label there. This is what it looks like:
https://people.freedesktop.org/~lkundrak/ariel-leds.jpeg

The green and amber, despite being packaged separately, can be
controlled independently (they are not connected to the same inputs in
reverse).

What does the machine do with stock firmware & ThinOS:
* On power on, EC lights up the Amber one & Blue one
* As soon as the firmware takes control, it turns off Amber and turns on
  Green
* Just before passing control to the OS, firmware turns the Green LED to
  blinking
* As soon as OS initializes, it turns Green back to always-on

Therefore the functionality generally is as follows:
* Amber is always off (only on for a short time between CPU on and
  firmware running)
- Green blinking means "loading OS", otherwise always on when CPU is on
- Blue is always on when the CPU is on

> > +	ret = devm_led_classdev_register(dev, &leds[2].led_cdev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	dev_info(dev, "Dell Wyse 3020 LEDs\n");
> > +	return 0;
> > +}
> 
> Just return ret; no need to print anything into the syslog.

Thanks for the comments -- I'll address them in the next version.

Take care!
Lubo

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