Re: [PATCH v5 04/13] Documentation: ABI: testing: add parent entry for iio channels

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 17 May 2026 19:37:48 +0100
Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:

> From: Rodrigo Alencar <rodrigo.alencar@analog.com>
> 
> Add documentation for a read-only sysfs attribute that allows to expose
> parent-child relationships between IIO channels.
> 
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-iio | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> index 925a33fd309a..399944974e34 100644
> --- a/Documentation/ABI/testing/sysfs-bus-iio
> +++ b/Documentation/ABI/testing/sysfs-bus-iio
> @@ -2118,6 +2118,19 @@ Description:
>  		specific attributes. This is useful for userspace to be able to
>  		better identify an individual channel.
>  
> +What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_parent
> +What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_parent
> +What:		/sys/bus/iio/devices/iio:deviceX/in_altvoltageY_parent
> +What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_parent
> +KernelVersion:	7.1
> +Contact:	linux-iio@vger.kernel.org
> +Description:
> +		Read-only attribute containing the label of the parent channel
> +		for hierarchical channel relationships. Only present on channels
> +		that have a parent channel with a valid label. This is useful for
> +		userspace to organize channels in tree-like structures that reflects
> +		the physical or logical relationships between them.

Perhaps an example would be useful?

Otherwise it seems reasonable.  One vague concern I have is maybe we end
up with a channel that actually has no other existence than as a parent.
Image two signals mixed into one.  If that mixed signal has nothing to control
it wouldn't normally show up in the ABI.

I guess we can give it a label though to ensure there is something there 
(even when not using labels for this!).

J

> +
>  What:		/sys/bus/iio/devices/iio:deviceX/in_phaseY_raw
>  KernelVersion:	4.18
>  Contact:	linux-iio@vger.kernel.org
>