linux-kernel - Re: [PATCH 1/2] leds: leds-multi-gpio: Add multiple GPIOs LED driver

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Message-ID: <20210324104016.GA6035@duo.ucw.cz>
Date:   Wed, 24 Mar 2021 11:40:16 +0100
From:   Pavel Machek <pavel@....cz>
To:     Marek Behun <marek.behun@....cz>
Cc:     Hermes Zhang <chenhui.zhang@...s.com>, dmurphy@...com,
        robh+dt@...nel.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        chenhuiz@...s.com, lkml@...s.com, kernel@...s.com
Subject: Re: [PATCH 1/2] leds: leds-multi-gpio: Add multiple GPIOs LED driver

Hi!

> > From: Hermes Zhang <chenhuiz@...s.com>
> > 
> > Introduce a new multiple GPIOs LED driver. This LED will made of
> > multiple GPIOs (up to 8) and will map different brightness to different
> > GPIOs states which defined in dts file.
> 
> I wonder how many boards have such LEDs.
> 
> Also if it wouldn't be better to expand the original leds-gpio driver.
> Probably depends on how much larger would such expansion make the
> leds-gpio driver.

Let's start with separate.

> Use flexible array members. Allocate with
>   devm_kzalloc(dev, struct_size(priv, states, priv->nr_states),
>                GFP_KERNEL)

Better yet, assume the brightness is 0..2^(num leds) and avoid this
complexity.

> Again LED_FULL and LED_OFF...
> What about default-state = "keep" ?
> 
> Hermes, do you actually have a device that controls LEDs this way? How
> many brightness options do they have?

He has two bits.

> Also I think this functionality could be easily incorporated into the
> existing leds-gpio driver, instead of creating new driver.

> Moreover your driver can control only one LED, so it needs to be
> probed multiple times for multiple LEDs. Meanwhile the leds-gpio driver
> can register multiple LEDs in one probe...

The current version is mostly fine. Let's not overcomplicate it.

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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