linux-kernel - Re: [BUG] Stuck key syndrome (was: Re: [PATCH net-next v2] net: dsa: microchip: Add SGMII port support to KSZ9477 switch)

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Message-ID: <CAHk-=wipkOP939yPWroH_u+CQGsJQRSa_BHsg4cLNPRPq86sAQ@mail.gmail.com>
Date: Wed, 7 May 2025 07:46:03 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>, 
	Woojung Huh <woojung.huh@...rochip.com>, Vladimir Oltean <olteanv@...il.com>, 
	Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Dmitry Torokhov <dmitry.torokhov@...il.com>, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] Stuck key syndrome (was: Re: [PATCH net-next v2] net: dsa:
 microchip: Add SGMII port support to KSZ9477 switch)

On Wed, 7 May 2025 at 04:51, Maxime Chevallier
<maxime.chevallier@...tlin.com> wrote:
>
> So, same as you, it'll take a long time for me to say with some amount
> of certainty that 'i8042_unlock=1' has a beneficial effect, of
> course unless I see the problem happen again in the meantime.

Christ. You'd expect that any i8042 issues had been fixed long ago,
but the problem is that the chip doesn't necessarily even exist in
modern platforms, and everybody just fakes it.

So the platform presumably still has hardware support for it, but it's
mostly in the form of "take a trap when accessing the legacy keyboard
ports, and fake it in firmware".

Although it doesn't help that there are literally decades of clone
chips and hacky real hardware that extended on the i8042 in various
more-or-less compatible ways.

Which makes all of these things almost entirely undebuggable.

I'm surprised the XPS9510 would be particularly troublesome - I've had
an XPS for years (older version, obviously) with no issues outside of
WiFi sometimes acting up. But random firmware...

I doubt it's "keylock active", but who knows. I get that on my xps
too, it's a random bit that doesn't really mean much. But - because of
all the reasons above - who knows...

One typical problem has been "the interrupt line is wired oddly", but
the fact that it apparently works *most* of the time means that that
is unlikely to be the issue here.

              Linus