Re: [PATCH v5 03/13] iio: core: add hierarchical channel relationships

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Exposing the hierarchical relationship via channel labels creates an ambiguous UAPI for userspace.
--

commit 64c6f961f1d7645c58f732e4bd4c11200b999e93
Author: Rodrigo Alencar <rodrigo.alencar@analog.com>

iio: core: add hierarchical channel relationships

This commit introduces a parent-child relationship between IIO channels.
It adds a parent pointer to the iio_chan_spec struct and exposes this
relationship to userspace through a new "parent" sysfs attribute that
returns the parent channel's label.

> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 5c8404efd0a56..348ac7a597385 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c

[ ... ]

> @@ -1263,6 +1271,31 @@ static int iio_device_add_channel_label(struct iio_dev *indio_dev,
>  	return 1;
>  }
>  
> +static int iio_device_add_channel_parent(struct iio_dev *indio_dev,
> +					 struct iio_chan_spec const *chan)
> +{
> +	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> +	int ret;
> +
> +	if (!chan->parent || (!indio_dev->info->read_label &&
> +			      !chan->parent->extend_name))
> +		return 0;

Is relying on channel labels robust enough for programmatic parent resolution?

IIO channel labels are optional, human-readable descriptors and are not
guaranteed by the core to be unique. If multiple channels within a device
share the same label, how can userspace definitively resolve which specific
channel is the parent?

Also, if a driver establishes a hierarchy where chan->parent is set, but the
parent channel lacks a label, this attribute is silently omitted, hiding the
relationship entirely.

Would it be more reliable to expose a definitive, unique identifier (such as
the parent channel's sysfs prefix or index) rather than relying on an optional
descriptive string?

> +
> +	ret = __iio_add_chan_devattr("parent",
> +				     chan,
> +				     &iio_read_channel_parent,
> +				     NULL,
> +				     0,
> +				     IIO_SEPARATE,
> +				     &indio_dev->dev,
> +				     NULL,
> +				     &iio_dev_opaque->channel_attr_list);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 1;
> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260517-ad9910-iio-driver-v5-0-31599c88314a@analog.com?part=3