Re: [PATCH v2 3/5] iio: Add channel type for attention

[David Lechner <dlechner@baylibre.com>]

On 10/29/24 9:38 AM, Jonathan Cameron wrote:
> On Tue, 29 Oct 2024 13:20:06 +0100
> Ricardo Ribalda <ribalda@chromium.org> wrote:
> 
>> Hi Jonathan
>>
>> On Mon, 28 Oct 2024 at 21:34, Jonathan Cameron <jic23@kernel.org> wrote:
>>>
>>> On Mon, 28 Oct 2024 10:12:23 +0000
>>> Ricardo Ribalda <ribalda@chromium.org> wrote:
>>>  
>>>> Add a new channel type representing if the user's attention state to the
>>>> the system. This usually means if the user is looking at the screen or
>>>> not.
>>>>
>>>> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
>>>> ---
>>>>  Documentation/ABI/testing/sysfs-bus-iio | 7 +++++++
>>>>  drivers/iio/industrialio-core.c         | 1 +
>>>>  include/uapi/linux/iio/types.h          | 1 +
>>>>  tools/iio/iio_event_monitor.c           | 2 ++
>>>>  4 files changed, 11 insertions(+)
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>>>> index 89943c2d54e8..d5a2f93bd051 100644
>>>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>>>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>>>> @@ -2339,3 +2339,10 @@ KernelVersion: 6.10
>>>>  Contact:     linux-iio@vger.kernel.org
>>>>  Description:
>>>>               The value of current sense resistor in Ohms.
>>>> +
>>>> +What:                /sys/.../iio:deviceX/in_attention_raw
>>>> +KernelVersion:       6.13
>>>> +Contact:     linux-iio@vger.kernel.org
>>>> +Description:
>>>> +             Boolean value representing the user's attention to the system.
>>>> +             This usually means if the user is looking at the screen or not.  
>>>
>>> Hmm. I should have thought of this when I replied to suggest a new channel type.
>>> The question is 'units' for a decision.
>>>
>>> Last time we hit something like this where processing is used to make a decision
>>> we decided to at least allow for the concept of 'certainty'.
>>>
>>> The idea being that smarter sensors would tell us something about how sure they
>>> are that the attention is on the device.
>>> The analogy being with activity detection. See in_activity_walking_input
>>> in Documentation/ABI/testing/sysfs-bus-iio
>>>
>>> Do you think that would be appropriate here as well?  For this device
>>> it would take the values 0 and 100 rather than 0 and 1.  
>>
>> For the particular device that I want to support, they are giving me a
>> value of 1 and 0, and the example from usb.org seems to work the same
>> way (Logical Maximum of 1)
>> https://www.usb.org/sites/default/files/hutrr107-humanpresenceattention_1.pdf
>>
>> I have no problem multiplying my value by 100 if you think there will
>> be a use case for that. It will not have a major performance impact on
>> the driver.
> Same was true (0 or 1) for the activity classification but I'm not
> keen on certainty :)  So lets' copy that precedence and *100
> 
> 
And I assume we would want this to be in_attention_input (processed),
not in_attention_raw.