netdev - Re: [PATCH v2] net: dsa: rtl8366rb: Fix compilation problem

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Message-ID: <20250220205855.hthx46nbghverspc@skbuf>
Date: Thu, 20 Feb 2025 22:58:55 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Alvin Šipraga <alsi@...g-olufsen.dk>,
	Andrew Lunn <andrew@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Luiz Angelo Daros de Luca <luizluca@...il.com>,
	netdev@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2] net: dsa: rtl8366rb: Fix compilation problem

On Thu, Feb 20, 2025 at 08:16:26PM +0100, Linus Walleij wrote:
> > IMHO, the code could use further simplification if "realtek,disable-leds" were
> > honored only with the LED subsystem enabled. I understand the property exists
> > prior to that, but it can be ignored if convenient. It seems reasonable to
> > leave LEDs as they are if CONFIG_LEDS_CLASS is disabled. But let me know
> > if you disagree, it's not a strong opinion.
> 
> I added it to the router for a reason: I found that the LEDs were enabled
> on the D-Link DIR-685 (boot on default), despite this device does not
> even have any physical LEDs mounted.
> 
> So it's there to save some (well, probably not much but not non-existent)
> leak current in the silicon and pads from the LED driver stages being
> activated despite they are unused. If they are even blinking, it's even
> more leak current for blinking the non-LEDs, running timers and what
> not.
> 
> That's why the binding looks like so:
> 
>   realtek,disable-leds:
>     type: boolean
>     description: |
>       if the LED drivers are not used in the hardware design,
>       this will disable them so they are not turned on
>       and wasting power.
> 
> This is maybe a bit perfectionist I know...

No, I understand, it is definitely more careful and perfectionist handling
than you'd expect of the situation where software support for LEDs
is compiled out of the kernel.

Anyway, are you using a custom-built kernel for this router? Do you
expect CONFIG_LEDS_CLASS to be disabled? I hope I'm not reading this
wrong, but I see current openwrt for dir-685 uses the same config-6.6
for the entire gemini target, which in my reading has CONFIG_LEDS_CLASS
enabled (well it explicitly only has CONFIG_PHYLIB_LEDS, which depends
on CONFIG_LEDS_CLASS).

I understand why you did it when you did it, and I'm not trying to push
any farther if you want it to remain that way, I'm just not clear whether
you understood that I'm asking whether it matters from a practical
perspective today.