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

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

Hi,

On 10/8/20 2:14 AM, Jeff LaBundy wrote:
> Hi all,
> 
> On Wed, Oct 07, 2020 at 03:32:07PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 10/7/20 3:29 PM, Bastien Nocera wrote:
>>> On Wed, 2020-10-07 at 15:08 +0200, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 10/7/20 1:35 PM, Bastien Nocera wrote:
>>>>> On Wed, 2020-10-07 at 11:51 +0200, Hans de Goede wrote:
>>>>>> <snip>
>>>>>>> Dmitry, any existing stuff like this in input?
> 
> It seems we are talking about "specific absorption rate" (SAR) type
> devices that signal the WLAN controller to reduce transmitted power
> while a user is nearby.

Yes and no. At least the lap-mode detection (laptop on someones
lap rather then sitting on a table) is currently used by the
embedded-controller for thermal management decisions, basically
when on someones lap the configurable TPD of the CPU is set lower
to keep the laptop's bottom skin temperate < 45 degrees Celsius
(I think it is 45 but the exact number does not matter).

The lap-mode info is currently exported with a thinkpad_acpi specific
sysfs attribute with the idea that userspace could potentially use
this to indicate to the user that turbo clocks will be lower
because of this.

With upcoming WLAN cards with configurable transmit power,
this will also be used as what you call a SAR device.

AFAIK the palmrest case is mostly a SAR device.

Note I'm explaining the alternative lap-mode use-case to make
sure everyone is on the same page. I completely agree with the
gist of your email :)

> I just wanted to chime in and confirm that we do have at least one
> precedent for these being in input (keyboard/iqs62x-keys) and not
> iio so I agree with Jonathan here. My argument is that we want to
> signal binary events (user grabbed onto or let go of the handset)
> rather than deliver continuous data.

I was curious what keycode you are using for this, but I see
that the keycodes come from devicetree, so I guess I should
just ask: what keycode are you using for this ?

> The example I've shown reports events as keycodes since some of the
> events it can express represent momentary conditions. In hindsight,
> however, an argument can be made to express some of this information
> as a switch (user is or is not near the device) and the new event
> codes proposed here seem like a step in the right direction.

I'm glad that you like the new proposed switch event-codes.

Regards,

Hans