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From: Hans de Goede <>
Cc: Mark Pearson <>,
	Bastien Nocera <>
Subject: Using IIO to export laptop palm-sensor and lap-mode info to userspace?
Date: Sat, 3 Oct 2020 16:02:37 +0200
Message-ID: <> (raw)

Hi All,

Modern laptops can have various sensors which are kinda
like proximity sensors, but not really (they are more
specific in which part of the laptop the user is
proximate to).

Specifically modern Thinkpad's have 2 readings which we
want to export to userspace, and I'm wondering if we
could use the IIO framework for this since these readings
are in essence sensor readings:

1. These laptops have a sensor in the palm-rests to
check if a user is physically proximate to the device's
palm-rests. This info will be used by userspace for WWAN
functionality to control the transmission level safely.

A patch adding a thinkpad_acpi specific sysfs API for this
is currently pending:

But I'm wondering if it would not be better to use
IIO to export this info.

2. These laptops have something called lap-mode, which
determines if the laptop's firmware thinks that it is on
a users lap, or sitting on a table. This influences the
max. allowed skin-temperature of the bottom of the laptop
and thus influences thermal management.  Like the palm-rest
snesors, this reading will likely also be used for
controlling wireless transmission levels in the future.

Note that AFAIK the lap_mode reading is not a single sensor
reading, it is a value derived from a bunch of sensor readings,
the raw values of which may or may not be available

So looking at existing IIO userspace API docs, focussing on
proximity sensors I see:


Where the latter seems to not really be relevant.

 From the generic IO API doc, this bit is the most

What:           /sys/.../iio:deviceX/in_proximity_raw
What:           /sys/.../iio:deviceX/in_proximity_input
What:           /sys/.../iio:deviceX/in_proximityY_raw
KernelVersion:  3.4
                 Proximity measurement indicating that some
                 object is near the sensor, usually by observing
                 reflectivity of infrared or ultrasound emitted.
                 Often these sensors are unit less and as such conversion
                 to SI units is not possible. Higher proximity measurements
                 indicate closer objects, and vice versa. Units after
                 application of scale and offset are meters.

This seems to be a reasonable match for the Thinkpad sensors
we are discussing here, although those report a simple
0/1 value.

What is missing for the ThinkPad case is something like this:

What:		/sys/.../iio:deviceX/proximity_sensor_location
KernelVersion:  5.11
		Specifies the location of the proximity sensor /
		specifies proximity to what the sensor is measuring.
		Reading this file returns a string describing this, valid values
		for this string are: "screen", "lap", "palmrest"
		Note the list of valid values may be extended in the

So what do you (IIO devs) think about this?

Would adding a proximity_sensor_location attribute be a reasonable
thing to do for this; and do you think that this would be a good idea ?



             reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-03 14:02 Hans de Goede [this message]
2020-10-06  2:04 ` [External] " Mark Pearson
2020-10-07  8:36   ` Jonathan Cameron
2020-10-07  9:51     ` Hans de Goede
2020-10-07 11:35       ` Bastien Nocera
2020-10-07 13:08         ` Hans de Goede
2020-10-07 13:29           ` Bastien Nocera
2020-10-07 13:32             ` Hans de Goede
2020-10-08  0:14               ` Jeff LaBundy
2020-10-08  7:10                 ` Hans de Goede
2020-10-09  2:19                   ` Jeff LaBundy
2020-10-12 12:13                     ` Hans de Goede
2020-10-12 12:36                   ` Enrico Weigelt, metux IT consult
2020-10-13  1:12                     ` Mark Pearson
2020-10-13  8:38                     ` Hans de Goede
2020-11-12  6:23       ` Dmitry Torokhov
2020-11-12  9:50         ` Hans de Goede
2020-11-13  6:58           ` Dmitry Torokhov
2020-11-19 15:39             ` Hans de Goede
2020-11-19 16:11               ` Bastien Nocera
2020-11-20  9:59               ` Jonathan Cameron
2020-11-23 12:16                 ` Hans de Goede
2020-11-23 16:07                   ` Jonathan Cameron
2020-11-19 15:16         ` Bastien Nocera
2020-11-19 15:24           ` Hans de Goede
2020-11-19 15:58             ` Bastien Nocera

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