linux-kernel - Re: [RFC PATCH] input: Add disable sysfs entry for every input device

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Date:   Mon, 2 Jan 2017 18:09:58 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Bastien Nocera <hadess@...ess.net>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Pavel Machek <pavel@....cz>,
        Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Chuck Ebbert <cebbert.lkml@...il.com>,
        Henrik Rydberg <rydberg@...omail.se>,
        Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] input: Add disable sysfs entry for every input device

On Monday 02 January 2017 16:27:05 Bastien Nocera wrote:
> On Sun, 2016-12-25 at 11:04 +0100, Pali Rohár wrote:
> > This patch allows user to disable events from any input device so
> > events
> > would not be delivered to userspace.
> > 
> > Currently there is no way to disable particular input device by
> > kernel.
> > User for different reasons would need it for integrated PS/2
> > keyboard or
> > touchpad in notebook or touchscreen on mobile device to prevent
> > sending
> > events. E.g. mobile phone in pocket or broken integrated PS/2
> > keyboard.
> > 
> > This is just a RFC patch, not tested yet. Original post about
> > motivation
> > about this patch is there: https://lkml.org/lkml/2014/11/29/92
> 
> Having implemented something of that ilk in user-space (we
> automatically disable touch devices when the associated screen is
> turned off/suspended), I think this might need more thought.

How to implement such thing in userspace? I think you cannot do that 
without rewriting every one userspace application which uses input.

> What happens when a device is opened and the device disabled through
> sysfs, are the users revoked?

Applications will not receive events. Same as if input device does not 
generates events.

> Does this put the device in suspend in the same way that closing the
> device's last user does?

Current code not (this is just RFC prototype), but it should be possible 
to implement.

> Is this not better implemented in user-space at the session level,
> where it knows about which output corresponds to which input device?

How to do that without rewriting existing applications?

> Is this useful enough to disable misbehaving devices on hardware, so
> that the device is not effective on boot?  

In case integrated device is absolutely unusable and generates always 
random events, it does not solve problem at boot time.

But more real case is laptop with closed LID press buttons and here it 
is useful.

-- 
Pali Rohár
pali.rohar@...il.com

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