linux-kernel - Re: [PATCH] Input: i8042 - disable active multiplexing by default

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Date:	Fri, 10 Oct 2014 14:02:31 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	linux-input@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Hans de Goede <hdegoede@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: i8042 - disable active multiplexing by default

On Fri, Oct 10, 2014 at 10:59:19PM +0200, Jiri Kosina wrote:
> On Fri, 10 Oct 2014, Dmitry Torokhov wrote:
> 
> > Active multiplexing is a nice feature as it allows several pointing devices
> > (such as touchpad and external mouse) use their native protocols at the
> > same time. Unfortunately many manufacturers do not implement the feature
> > properly even though they advertise it. The problematic implementations are
> > never fixed, since Windows by default does not use this mode, and move from
> > one BIOS/model of laptop to another. When active multiplexing is broken
> > turning it on usually results in touchpad, keyboard, or both unresponsive.
> > 
> > With PS/2 usage on decline (most of PS/2 devices in use nowadays are
> > internal laptop touchpads), I expect number of users who have laptops with
> > working MUX implementation, docking stations with external PS/2 ports, and
> > who are still using external PS/2 mice, to be rather small. Let's flip the
> > default to be OFF and allow activating it through i8042.nomux=0 kernel
> > option.  We'll also keep DMI table where we can record known good models.
> 
> Being responsible for introducing a non-trivial portion of 
> i8042_dmi_nomux_table[] entries:
> 
> 	Acked-by: Jiri Kosina <jkosina@...e.cz>
> 
> If nothing else, it'd make my life easier :)
> 
> [ ... snip ... ]
> > diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
> > index f5a98af..9a97c2b 100644
> > --- a/drivers/input/serio/i8042.c
> > +++ b/drivers/input/serio/i8042.c
> > @@ -39,7 +39,7 @@ static bool i8042_noaux;
> >  module_param_named(noaux, i8042_noaux, bool, 0);
> >  MODULE_PARM_DESC(noaux, "Do not probe or use AUX (mouse) port.");
> >  
> > -static bool i8042_nomux;
> > +static bool i8042_nomux = true;
> 
> Hmmm ... perhaps if we want to be really friendly, we should warn (and I 
> definitely don't mean WARN(), but rather pr_info() or something) if we 
> encounter that the cmdline contains 'i8042.nomux=1'.

Warn about what? That they do not need this option anymore? They might
if they downgrade the kernel. I would not bother...

Thanks.

-- 
Dmitry
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