Re: [PATCH v9 08/17] iio: core: add hierarchical channel relationships

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 22 Jul 2026 16:50:17 +0100
Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@kernel.org> wrote:

> From: Rodrigo Alencar <rodrigo.alencar@analog.com>
> 
> Add parent-child relationship between iio channels by creating a parent
> pointer field in iio_chan_spec struct and exposing a sysfs attribute that
> returns the parent channel prefix.
> 
> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@analog.com>
Hi Rodrigo.

One small thing below

Jonathan

> ---
>  drivers/iio/industrialio-core.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  include/linux/iio/iio.h         |  5 +++++
>  2 files changed, 45 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index aa9d6474edd9..f7e3048354b9 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -856,6 +856,22 @@ static ssize_t iio_read_channel_label(struct device *dev,
>  					 to_iio_dev_attr(attr)->c, buf);
>  }
>  
> +static ssize_t iio_read_channel_parent(struct device *dev,
> +				       struct device_attribute *attr,
> +				       char *buf)
> +{
> +	const struct iio_chan_spec *chan = to_iio_dev_attr(attr)->c->parent;
> +	ssize_t len;
> +
> +	len = __iio_chan_prefix_emit(dev, chan, IIO_SEPARATE, buf, PAGE_SIZE);
> +	if (len < 0)
> +		return len;
> +
> +	buf[len++] = '\n';

Use sysfs_emit_at() for this rather than a direct write. I'd rather not have
to think about what happens if __iio_chan_prefix_emit() returns exactly
PAGE_SIZE().

> +
> +	return len;
> +}
> +