linux-kernel - Re: [RFC PATCH v1 7/9] iio: Expand IIO event interface for real-world unit handling

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Message-ID: <5835e21b-0b27-41f5-8c92-762cac327b40@baylibre.com>
Date: Sun, 18 Jan 2026 14:10:30 -0600
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt1@...il.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: jic23@...nel.org, Jonathan.Cameron@...wei.com, nuno.sa@...log.com,
 andy@...nel.org
Subject: Re: [RFC PATCH v1 7/9] iio: Expand IIO event interface for real-world
 unit handling

On 1/18/26 12:21 PM, Marcelo Schmitt wrote:
> The IIO event ABI documentation distinguishes between interfaces that
> handle values in device-specific units (_raw) and event interfaces that
> handle values in real-world units (e.g. meters, Joules, lux, etc).
> However, the IIO event code infrastructure had never really implemented the
> bits to distinguish between those two types of interfaces and had always
> presumed events to handle raw device values.
> 
> For most current use cases, assuming events to handle values in device raw
> units is reasonable because it often matches the type of the associated IIO
> channel. There are a few cases where drivers provide events along side
> channels with both _raw and _input interfaces, though. Also, when
> real-world values can be mapped back to device configurations, it enables
> drivers to provide event interfaces that are arguably easier to use.
> 
> Expand the IIO events support, enabling IIO drivers to provide event
> interfaces that handle values in real-world units.
> 

...

> @@ -399,15 +410,23 @@ static int iio_device_add_event(struct iio_dev *indio_dev,
>  	for_each_set_bit(i, mask, sizeof(*mask)*8) {
>  		if (i >= ARRAY_SIZE(iio_ev_info_text))
>  			return -EINVAL;
> -		if (dir != IIO_EV_DIR_NONE)
> -			postfix = kasprintf(GFP_KERNEL, "%s_%s_%s",
> -					iio_ev_type_text[type],
> -					iio_ev_dir_text[dir],
> -					iio_ev_info_text[i]);
> -		else
> +		if (dir != IIO_EV_DIR_NONE) {
> +			if (i == IIO_EV_INFO_ENABLE)
> +				postfix = kasprintf(GFP_KERNEL, "%s_%s_%s",
> +						iio_ev_type_text[type],
> +						iio_ev_dir_text[dir],
> +						iio_ev_info_text[i]);
> +			else
> +				postfix = kasprintf(GFP_KERNEL, "%s_%s_%s_%s",
> +						iio_ev_unit_text[unit],
> +						iio_ev_type_text[type],
> +						iio_ev_dir_text[dir],
> +						iio_ev_info_text[i]);
> +		} else {

I think that the units only make sense on IIO_EV_INFO_VALUE and
IIO_EV_INFO_HYSTERESIS. Everything else has it's own unit, not just
IIO_EV_INFO_ENABLE.

>  			postfix = kasprintf(GFP_KERNEL, "%s_%s",
>  					iio_ev_type_text[type],
>  					iio_ev_info_text[i]);
> +		}
>  		if (postfix == NULL)
>  			return -ENOMEM;
>