linux-kernel - Re: [PATCH] Input: cros_ec_keyb: Add support for a front proximity switch

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Message-ID: <X/dlKKeAHU/Ab+VD@google.com>
Date:   Thu, 7 Jan 2021 11:46:48 -0800
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Benson Leung <bleung@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH] Input: cros_ec_keyb: Add support for a front proximity
 switch

On Thu, Jan 07, 2021 at 06:57:10AM -0800, Doug Anderson wrote:
> Hi,
> 
> On Wed, Jan 6, 2021 at 6:22 PM Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> >
> > Hi Doug, Stephen,
> >
> > On Wed, Jan 06, 2021 at 05:16:10PM -0800, Doug Anderson wrote:
> > > Hi,
> > >
> > > On Fri, Dec 4, 2020 at 4:48 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > > >
> > > > Some cros ECs support a front proximity MKBP event via
> > > > 'EC_MKBP_FRONT_PROXIMITY'. Map this to the 'SW_FRONT_PROXIMITY' input
> > > > event code so it can be reported up to userspace.
> > > >
> > > > Cc: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > > > Cc: Benson Leung <bleung@...omium.org>
> > > > Cc: Guenter Roeck <groeck@...omium.org>
> > > > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > > > ---
> > > >  drivers/input/keyboard/cros_ec_keyb.c          | 5 +++++
> > > >  include/linux/platform_data/cros_ec_commands.h | 1 +
> > > >  2 files changed, 6 insertions(+)
> > >
> > > This seems really straightforward.
> > >
> > > Reviewed-by: Douglas Anderson <dianders@...omium.org>
> > >
> > > Given that it touches a header file owned by the Chrome OS maintainers
> > > and a driver owned by input, how should it land?  One maintainer Acks
> > > and the other lands?
> >
> > Sorry about missing this one, however the "front proximity" switch has
> > been introduced for the benefit of phone devices, to be emitted when a
> > device is raised to user's ear, and I do not think we should be using
> > this here.
> >
> > We have just recently had similar discussion with regard to palm- and
> > lap-mode sensors and whether they should be reported over input or IIO
> > as true proximity sensors:
> >
> > https://lore.kernel.org/linux-iio/9f9b0ff6-3bf1-63c4-eb36-901cecd7c4d9@redhat.com/
> >
> > Based on what we are doing for other Chrome OS devices that expose
> > proximity sensors (for example trogdor) we have decided that we all
> > should be using IIO as it will allow not only on/off, but true proximity
> > reporting with potential of implementing smarter policies by userspace.
> >
> > Because of that we should do the same here and export this as IIO
> > proximity sensor as well.
> 
> For devices with a true proximity sensor that's exactly what we're
> doing.  I've only been involved in the periphery of the discussion,
> but as I understand it there are some models of laptop for which we
> don't have a true proximity sensor.  On these devices, the EC is in
> charge of deciding about proximity based on a number of factors.

Yes, I understand that on some devices the proximity sensors are not
true sensors but rather on/off signals, potentially derived from a
multitude of sources. However there is still a benefit in exposing them
as IIO proximity devices with limited reporting representing
[near, infinity] range/values. This will mean that userspace needs to
monitor only one set of devices (IIO) instead of both IIO and input, and
will not require constantly expanding EV_SW set to account for
ever-growing number of proximity sensors (lap, palm, general presence,
etc).

Thanks.

-- 
Dmitry