linux-kernel - Re: [PATCH 0/4] platform/x86: intel-vbtn: Add support for several more switches/buttons

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Message-ID: <1509982614.2869.120.camel@hadess.net>
Date:   Mon, 06 Nov 2017 16:36:54 +0100
From:   Bastien Nocera <hadess@...ess.net>
To:     Brüns, Stefan <Stefan.Bruens@...h-aachen.de>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Andy Shevchenko <andy@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        AceLan Kao <acelan.kao@...onical.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input <linux-input@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>
Subject: Re: [PATCH 0/4] platform/x86: intel-vbtn: Add support for several
 more switches/buttons

On Mon, 2017-11-06 at 15:25 +0000, Brüns, Stefan wrote:
> On Montag, 6. November 2017 13:54:25 CET Bastien Nocera wrote:
> > On Sun, 2017-11-05 at 14:31 +0200, Andy Shevchenko wrote:
> > > On Fri, Nov 3, 2017 at 9:03 PM, Stefan Brüns
> > > 
> > > <stefan.bruens@...h-aachen.de> wrote:
> > > > Currently, intel-vbtn only supports the most relevant buttons,
> > > > although
> > > > there are several more events, mostly in use by convertibles.
> > > > 
> > > > This series adds support for three more events. One of these
> > > > events
> > > > is a switch (SW_*) event, which is currently not working when
> > > > using
> > > > sparse keymaps. The first patch fixes this combination.
> > > > 
> > > > The second patch adds support for the SW_TABLET_MODE switch,
> > > > which
> > > > is used by current convertibles.
> > > > 
> > > > The third patch adds support for the KEY_ROTATE_DISPLAY. On the
> > > > Dell
> > > > XPS 12 (9Q33), rotation lock is implemented as a button to
> > > > toggle
> > > > between locked and unlocked state. In locked state, the
> > > > accelerometer
> > > > should be ignored, while in unlocked the screen contents should
> > > > autorotate based on the tablet orientation. The same
> > > > functionality
> > > > is likely implemented as a switch (SW_ROTATE_LOCK event) on
> > > > different
> > > > hardware.
> > > > 
> > > > The fourth patch adds support for the "Windows logo" button/key
> > > > found on
> > > > the XPS 12 display (i.e. in tablet mode, it is the only key
> > > > reachable).
> > > > The Lenovo Helix 2 has an equivalent touch button. The event
> > > > currently
> > > > uses KEY_MENU, although a distinct key code may be a better
> > > > choice.
> > > 
> > > All, except first, are applied to my review and testing queue,
> > > thanks!
> > > 
> > > > Stefan Brüns (4):
> > > >   Input: sparse-keymap - send sync event for KE_SW/KW_VSW
> > > >   platform/x86: intel-vbtn: support SW_TABLET_MODE
> > > >   platform/x86: intel-vbtn: support KEY_ROTATE_DISPLAY
> > > >   platform/x86: intel-vbtn: support panel front button
> > 
> > KEY_MENU is the key for the contextual menu. You need to use
> > KEY_LEFTMETA. See 791738be57473fddaf393dcedcef31b577231aaa which
> > does
> > this for soc_button_array.
> 
> IMHO LEFTMETA is a bad idea for several reasons:
> 
> - LEFTMETA aka Windows aka RightGUI key is used as a modifier/flag
> (see e.g. 
> USB HID HUT, Keyboard Page 0x07), while on a tablet, it is the only
> regular 
> button (save special funtions like power, volume).

It isn't. There are a number of functions that can be triggered using
the Windows key + other buttons on the device, such as:

 ⊞ Win+PrtScr or ⊞ Win+Volume up instantly saves a screenshot to the
"Screenshots" folder in "Pictures" library. All screenshots are saved
as PNG files.

(from https://en.wikipedia.org/wiki/Windows_key#Windows_8)

In Windows, the button behaves the exact same way as the Windows key on
a keyboard would.

> - on a regular keyboard, I expect the LEFTMETA key to be
> handled/usable as a 
> modifier key. I would not expect it to be used as a shortcut key.
> 
> So if KEY_MENU is not acceptable, a new keycode IMHO is a much better
> option.
> 
> Kind regards,
> 
> Stefan
>