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@xxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxx 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
