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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 11/20/20 10:59 AM, Jonathan Cameron wrote:
> On Thu, 19 Nov 2020 16:39:07 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:

>>>>>>>> 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.  

<snip>

>>> On newer ARM we use "label" attribute in DTS:
>>>
>>> arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
>>>
>>>         ap_sar_sensor: proximity@28 {
>>>                 compatible = "semtech,sx9310";
>>>                 reg = <0x28>;
>>>                 #io-channel-cells = <1>;
>>>                 pinctrl-names = "default";
>>>                 pinctrl-0 = <&p_sensor_int_l>;
>>>
>>>                 interrupt-parent = <&tlmm>;
>>>                 interrupts = <24 IRQ_TYPE_LEVEL_LOW>;
>>>
>>>                 vdd-supply = <&pp3300_a>;
>>>                 svdd-supply = <&pp1800_prox>;
>>>
>>>                 status = "disabled";
>>>                 label = "proximity-wifi";
>>>         };  
>>
>> Hmm, interesting. I did not know iio-devices could
>> have a label sysfs attribute (nor that that could be
>> set through device-tree). I was thinking about adding
>> an in_proximity_location sysfs attribute. But using
>> labels (and standardizing a set of label names) will
>> work nicely too.
> 
> It's fairly new.   Note we also have per channel labels
> though they are 'very new'.  Might be handy if the sensors
> appear as a single device despite being spread over the
> laptop.

Interesting, the thinkpad_acpi stuff currently has 2
proximity(ish) sensors:

1. Laptop is close to (on) someones lap
2. Someone's arms are resting on or close to the palmrest

Ideally we would indeed register 1 iio-dev with separate
channels for this, rather then having to register 2
(and the future maybe even more) iio-devs for this.

Can you give a pointer to docs / examples of using a
label per channel ?

>> Is there a know set of labels which ChromeOS is currently
>> using? If we are going to use labels for this it would
>> be good IMHO to define a set of standard labels for
>> this in say Documentation/ABI/testing/sysfs-bus-iio-labels.
> 
> If you do want to do this, please just put it under sysfs-bus-iio
> doc.  I want this to be in the top level doc.

Ok, ack.

Dmitry, can you perhaps dig up a full-list of labels
which ChromeOS is currently using to identify
proximity sensors for e.g. SAR related use?

Regards,

Hans