linux-kernel - Re: [PATCH 1/1] platform/x86: revert pcengines-apuv2 wire up simswitch gpio as led

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Date:   Fri, 31 Jul 2020 15:45:56 +0200
From:   "Enrico Weigelt, metux IT consult" <lkml@...ux.net>
To:     Florian Eckert <fe@....tdt.de>, info@...ux.net,
        vhart@...radead.org, andy@...radead.org,
        Eckert.Florian@...glemail.com
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] platform/x86: revert pcengines-apuv2 wire up
 simswitch gpio as led

On 13.07.20 10:50, Florian Eckert wrote:

Hello Florian,

> This reverts commit 5037d4ddda31c2dbbb018109655f61054b1756dc.

no, please dont.

> This change connects the simswap to the LED subsystem of the kernel.
> From my point of view, it's nonsense. If we do it this way, then this
> can be switched relatively easily via the LED subsystem (trigger:
> none/default-on) and that is dangerous! If this is used, it would be
> unfavorable, since there is also another trigger (trigger:
> heartbeat/netdev).

I don't think that potential silly abuse is a good argument. It if
would, we should also disallow things like "echo FOO > /dev/sda" :p

The reason for it wire'ing up was having an simple and easy to use
interface. Raw gpios do NOT meet this criteria: complicated to use and
not stable addressing (from userland PoV) - would require an extra
userland program just for that single specific task.

Yes, LED is not the optimal approach, same for other gpio-connected
switches, eg. relais or various multiplexers. But as long as we don't
have a really fitting subsystem, it's IMHO the best compromise we have
so far.

Actually, I've already been hacking on a better subsystem, which models
switchable inter-device connections. It's called portmux. But it's not
usable yet. Lets talk about this instead of just wildly dropping
existing functionality, that's used in the field.

--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@...ux.net -- +49-151-27565287