[PATCH v7 03/17] iio: ABI: add parent entry for iio channels

[Rodrigo Alencar via B4 Relay]

From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-bus-iio | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index 3037b8b79fba..623167355d71 100644
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -2155,6 +2155,33 @@ 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
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_parent
+What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_parent
+What:		/sys/bus/iio/devices/iio:deviceX/in_altcurrentY_parent
+What:		/sys/bus/iio/devices/iio:deviceX/out_altcurrentY_parent
+KernelVersion:	7.2
+Contact:	linux-iio@xxxxxxxxxxxxxxx
+Description:
+		Read-only attribute containing the sysfs name prefix of the parent
+		channel for hierarchical channel relationships (e.g. "out_altvoltage0").
+		The prefix uniquely identifies the parent channel and can be used by
+		userspace to organize channels in tree-like structures that reflects
+		virtual or logical relationships between them.
+
+		For example, an IIO device may expose a primary output channel as
+		"out_voltage0" together with a set of profile-based or mode-based
+		subchannels used to configure or compose the output signal. These
+		subchannels may carry common attributes such as frequency, phase, etc.
+		They do not represent physical outputs, but rather logical/virtual
+		channels grouping configurations that affect the primary output.
+		Each subchannel exposes a *_parent attribute reading "out_voltage0",
+		allowing userspace to group controls under the output channel they
+		belong to rather than treating them as unrelated top-level channels.
+
 What:		/sys/bus/iio/devices/iio:deviceX/in_phaseY_raw
 KernelVersion:	4.18
 Contact:	linux-iio@xxxxxxxxxxxxxxx

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2.43.0