Re: [External] Using IIO to export laptop palm-sensor and lap-mode info to userspace?

[Mark Pearson <markpearson@lenovo.com>]

Adding Nitin, lead for this feature, to the thread

On 2020-10-03 10:02 a.m., Hans de Goede wrote:
> 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:
> https://patchwork.kernel.org/patch/11722127/
> 
> 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
> separately.
> 
> So looking at existing IIO userspace API docs, focussing on
> proximity sensors I see:
> 
> Documentation/ABI/testing/sysfs-bus-iio
> Documentation/ABI/testing/sysfs-bus-iio-proximity-as3935
> 
> Where the latter seems to not really be relevant.
> 
>  From the generic IO API doc, this bit is the most
> interesting:
> 
> What:           /sys/.../iio:deviceX/in_proximity_raw
> What:           /sys/.../iio:deviceX/in_proximity_input
> What:           /sys/.../iio:deviceX/in_proximityY_raw
> KernelVersion:  3.4
> Contact:        linux-iio@vger.kernel.org
> Description:
>                  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
> Contact:        linux-iio@vger.kernel.org
> Description:
>          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
>          future.
> 
> 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 ?
> 
> Regards,
> 
> Hans
>