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

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Date:   Wed, 03 Jan 2018 02:47:29 +0100
From:   Bastien Nocera <hadess@...ess.net>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        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>,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] input: Add disable sysfs entry for every input
 device

On Tue, 2018-01-02 at 22:54 +0100, Pali Rohár wrote:
> On Wednesday 04 January 2017 15:37:35 Bastien Nocera wrote:
> > I don't doubt that the use cases should be catered for, I
> > essentially
> > did that same work without kernel changes for GNOME. What I doubt
> > is
> > the fuzzy semantics, the fact that the device is kept opened but no
> > data is sent (that's not power saving), that whether users are
> > revoked
> > or should be revoked isn't clear, and that the goal is basically to
> > work around stupid input handling when at the console. When running
> > a
> > display manager, this is all avoided.
> > 
> > If this were to go through, then the semantics and behaviour needs
> > to
> > be better explained, power saving actually made possible, and make
> > sure
> > that libinput can proxy that state to the users on the console. Or
> > an
> > ioctl added to the evdev device to disable them.
> 
> So, do you mean to implement this "disable" action as ioctl for
> particular /dev/input/event* device (instead of sysfs entry)?

Yes, so the device can be powered down without the device node being
closed and made unavailable. I don't know whether that's something
that's already possible for all cases, but there's already
opportunistic in a lot of drivers and subsystems.

This opens up a whole new wave of potential problems, but it's a more
generally useful mechanism, I would think.