Re: [PATCH v4 03/10] iio: adc: add helpers for parsing ADC nodes

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 24 Feb 2025 20:33:16 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> There are ADC ICs which may have some of the AIN pins usable for other
> functions. These ICs may have some of the AIN pins wired so that they
> should not be used for ADC.
> 
> (Preferred?) way for marking pins which can be used as ADC inputs is to
> add corresponding channels@N nodes in the device tree as described in
> the ADC binding yaml.
> 
> Add couple of helper functions which can be used to retrieve the channel
> information from the device node.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
> 
> ---
> Revision history:
> v3 => v4:
>  - Drop diff-channel support
>  - Drop iio_adc_device_channels_by_property()
>  - Add IIO_DEVICE namespace
>  - Move industrialio-adc.o to top of the Makefile
>  - Some styling as suggested by Andy
>  - Re-consider included headers
> v2 => v3: Mostly based on review comments by Jonathan
>  - Support differential and single-ended channels
>  - Rename iio_adc_device_get_channels() as
>    iio_adc_device_channels_by_property()
>  - Improve spelling
>  - Drop support for cases where DT comes from parent device's node
>  - Decrease loop indent by reverting node name check conditions
>  - Don't set 'chan->indexed' by number of channels to keep the
>    interface consistent no matter how many channels are connected.
>  - Fix ID range check and related comment
> RFC v1 => v2:
>  - New patch
> 
> iio: adc: helper: drop headers
> ---
>  drivers/iio/adc/Kconfig            |  3 +
>  drivers/iio/adc/Makefile           |  2 +
>  drivers/iio/adc/industrialio-adc.c | 89 ++++++++++++++++++++++++++++++
>  include/linux/iio/adc-helpers.h    | 22 ++++++++
>  4 files changed, 116 insertions(+)
>  create mode 100644 drivers/iio/adc/industrialio-adc.c
>  create mode 100644 include/linux/iio/adc-helpers.h
> 
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 849c90203071..37b70a65da6f 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -6,6 +6,9 @@
>  
>  menu "Analog to digital converters"
>  
> +config IIO_ADC_HELPER
> +	tristate
> +
>  config AB8500_GPADC
>  	bool "ST-Ericsson AB8500 GPADC driver"
>  	depends on AB8500_CORE && REGULATOR_AB8500
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index ee19afba62b7..1c410f483029 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -3,6 +3,8 @@
>  # Makefile for IIO ADC drivers
>  #
>  
> +obj-$(CONFIG_IIO_ADC_HELPER) += industrialio-adc.o
> +
>  # When adding new entries keep the list in alphabetical order
>  obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o
>  obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
> diff --git a/drivers/iio/adc/industrialio-adc.c b/drivers/iio/adc/industrialio-adc.c
> new file mode 100644
> index 000000000000..d8e9e6825d2b
> --- /dev/null
> +++ b/drivers/iio/adc/industrialio-adc.c
> @@ -0,0 +1,89 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Helpers for parsing common ADC information from a firmware node.
> + *
> + * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com>
> + */
> +
> +#include <linux/device.h>
> +#include <linux/errno.h>
> +#include <linux/export.h>
> +#include <linux/module.h>
> +#include <linux/property.h>
> +#include <linux/types.h>
> +
> +#include <linux/iio/adc-helpers.h>
> +#include <linux/iio/iio.h>
> +
> +int iio_adc_device_num_channels(struct device *dev)
> +{
> +	return device_get_child_node_count_named(dev, "channel");
> +}
> +EXPORT_SYMBOL_GPL(iio_adc_device_num_channels);
Just noticed, this isn't namespaces which is a bit odd.  I'd drop
the export anyway in favour of static inline but if you don't match
the namespace of the next one.