Re: [PATCH 1/2] iio: documentation: Document proximity sensor label use

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

Hi,

On 2/12/21 7:46 PM, Jonathan Cameron wrote:
> On Sun,  7 Feb 2021 13:37:19 +0100
> Hans de Goede <hdegoede@redhat.com> wrote:
> 
>> Add an entry to Documentation/ABI/testing/sysfs-bus-iio for
>> the new device and channel label sysfs-attribute support.
>>
>> And document the standardized labels which may be used with proximity
>> sensors to hint userspace about the intended use of the sensor.
>>
>> Using labels to differentiate between the multiple proximity sensors
>> which a modern laptop/tablet may have was discussed in this thread:
>> https://lore.kernel.org/linux-iio/9f9b0ff6-3bf1-63c4-eb36-901cecd7c4d9@redhat.com/
>>
>> As mentioned the "proximity-wifi*" labels are already being used in
>> this manner on some chromebooks, see e.g.:
>> arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
>> arch/arm64/boot/dts/qcom/sc7180-trogdor-lte-sku.dtsi
>>
>> And the "proximity-palmrest" and "proximity-lap" labels are intended
>> to be used with the lap and palmrest sensors found in recent Lenovo
>> ThinkPad models.
>>
>> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
>> Cc: Mark Pearson <mpearson@lenovo.com>
>> Cc: Bastien Nocera <hadess@hadess.net>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>  Documentation/ABI/testing/sysfs-bus-iio | 41 +++++++++++++++++++++++++
>>  1 file changed, 41 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
>> index 35289d47d6cb..f2f090f8bd2f 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>> @@ -33,6 +33,47 @@ Description:
>>  		Description of the physical chip / device for device X.
>>  		Typically a part number.
>>  
>> +What:		/sys/bus/iio/devices/iio:deviceX/label
>> +What:		/sys/bus/iio/devices/iio:deviceX/in_*_label
>> +What:		/sys/bus/iio/devices/iio:deviceX/out_*_label
> 
> I was a bit in two minds about this from an organizational point of view.
> 1) Whether to separate the general label where position tends to make sense
>    from the channel labels.  May be something we want to do in future but we can probably
>    let that go for now.
> 2) Whether to allow such broad wild cards for the channels.
>    Whilst in theory any channel can have a label we normally only document ABI
>    that actually exists (mostly to know what we might break if we change anything :)
>    Still I can't see any way we can change this without breakage so in this
>    one case let's let the broad wild card go in.
> 
> This comes unstuck on the fact it overlaps with existing more specific Docs.
> 
> So can you pull the channel part out of here for v2.
> /sys/bus/iio/devices/iio:deviceX/in_voltageY_label
> /sys/bus/iio/devices/iio:deviceX/in_anglY_label

The problem is that these labels may either be used on a whole device,
which is certainly the case with the accelerometers in patch 2/2 where
the x y and z channels obviously all are either "accel-base" or
"accel-display".

Where as for proximity sensors the labels could be either applied at the
device level, or at a channel level.

The existing chromebook proximity usage is applying a label for this
at the device level.

This does mean that atm all users of this are using device-level labels;
and maybe I'm reading too much in your request. I guess that for now
I can just drop these lines for v2 :

What:		/sys/bus/iio/devices/iio:deviceX/in_*_label
What:		/sys/bus/iio/devices/iio:deviceX/out_*_label

Is that what you have in mind ?

Or do you want me to split this up in a proximity sensor case and an
accel case, and group both cases together with other proximity / accel
sensor attributes ?

Regards,

Hans




> Jonathan
>> +KernelVersion:	5.8
>> +Contact:	linux-iio@vger.kernel.org
>> +Description:
>> +		Optional symbolic label for a device or a channel.
>> +		This is useful for userspace to be able to better identify an
>> +		individual device or channel.
>> +
>> +		The contents of the label are free-form, but there are some
>> +		standardized uses:
>> +
>> +		For proximity sensors which give the proximity (of a person) to
>> +		a certain wlan or wwan antenna the following standardized labels
>> +		are used:
>> +
>> +		* "proximity-wifi"
>> +		* "proximity-lte"
>> +		* "proximity-wifi-lte"
>> +		* "proximity-wifi-left"
>> +		* "proximity-wifi-right"
>> +
>> +		These are used to indicate to userspace that these proximity
>> +		sensors may be used to tune transmit power to ensure that
>> +		Specific Absorption Rate (SAR) limits are honored.
>> +		The "-left" and "-right" labels are for devices with multiple
>> +		antennas.
>> +
>> +		In some laptops/tablets the standardized proximity sensor labels
>> +		instead	indicate proximity to a specific part of the device:
>> +
>> +		* "proximity-palmrest" indicates proximity to the keyboard's palmrest
>> +		* "proximity-palmrest-left" indicates proximity to the left part of the palmrest
>> +		* "proximity-palmrest-right" indicates proximity to the right part of the palmrest
>> +		* "proximity-lap" indicates the device is being used on someone's lap
>> +
>> +		Note "proximity-lap" is special in that its value may be
>> +		calculated by firmware from other sensor readings, rather then
>> +		being a raw sensor reading.
>> +
>>  What:		/sys/bus/iio/devices/iio:deviceX/current_timestamp_clock
>>  KernelVersion:	4.5
>>  Contact:	linux-iio@vger.kernel.org
>