[PATCH v6 03/10] iio: adc: add helpers for parsing ADC nodes

[PATCH v6 03/10] iio: adc: add helpers for parsing ADC nodes

[Matti Vaittinen]

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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:
v5 => v6:
 - Adapt to changed fwnode helper names
 - Fix spelling
v4 => v5:
 - Inline iio_adc_device_num_channels()
 - Fix Indenting function parameters
 - Combine the max channel ID checks.
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
---
 drivers/iio/adc/Kconfig            |  3 ++
 drivers/iio/adc/Makefile           |  2 +
 drivers/iio/adc/industrialio-adc.c | 79 ++++++++++++++++++++++++++++++
 include/linux/iio/adc-helpers.h    | 27 ++++++++++
 4 files changed, 111 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..6cfb001c74b9
--- /dev/null
+++ b/drivers/iio/adc/industrialio-adc.c
@@ -0,0 +1,79 @@
+// 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>
+
+/**
+ * devm_iio_adc_device_alloc_chaninfo_se - allocate and fill iio_chan_spec for ADC
+ *
+ * Scan the device node for single-ended ADC channel information. Channel ID is
+ * expected to be found from the "reg" property. Allocate and populate the
+ * iio_chan_spec structure corresponding to channels that are found. The memory
+ * for iio_chan_spec structure will be freed upon device detach.
+ *
+ * @dev:		Pointer to the ADC device.
+ * @template:		Template iio_chan_spec from which the fields of all
+ *			found and allocated channels are initialized.
+ * @max_chan_id:	Maximum value of a channel ID. Use -1 if no checking
+ *			is required.
+ * @cs:			Location where pointer to allocated iio_chan_spec
+ *			should be stored.
+ *
+ * Return:	Number of found channels on success. Negative value to indicate
+ *		failure.
+ */
+int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev,
+					  const struct iio_chan_spec *template,
+					  int max_chan_id,
+					  struct iio_chan_spec **cs)
+{
+	struct iio_chan_spec *chan_array, *chan;
+	int num_chan = 0, ret;
+
+	num_chan = iio_adc_device_num_channels(dev);
+	if (num_chan < 1)
+		return num_chan;
+
+	chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array),
+				  GFP_KERNEL);
+	if (!chan_array)
+		return -ENOMEM;
+
+	chan = &chan_array[0];
+
+	device_for_each_named_child_node_scoped(dev, child, "channel") {
+		u32 ch;
+
+		ret = fwnode_property_read_u32(child, "reg", &ch);
+		if (ret)
+			return ret;
+
+		if (max_chan_id != -1 && ch > max_chan_id)
+			return -ERANGE;
+
+		*chan = *template;
+		chan->channel = ch;
+		chan++;
+	}
+
+	*cs = chan_array;
+
+	return num_chan;
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER");
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>");
+MODULE_DESCRIPTION("IIO ADC fwnode parsing helpers");
diff --git a/include/linux/iio/adc-helpers.h b/include/linux/iio/adc-helpers.h
new file mode 100644
index 000000000000..56b092a2a4c4
--- /dev/null
+++ b/include/linux/iio/adc-helpers.h
@@ -0,0 +1,27 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+/*
+ * The industrial I/O ADC firmware property parsing helpers
+ *
+ * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com>
+ */
+
+#ifndef _INDUSTRIAL_IO_ADC_HELPERS_H_
+#define _INDUSTRIAL_IO_ADC_HELPERS_H_
+
+#include <linux/property.h>
+
+struct device;
+struct iio_chan_spec;
+
+static inline int iio_adc_device_num_channels(struct device *dev)
+{
+	return device_get_named_child_node_count(dev, "channel");
+}
+
+int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev,
+					  const struct iio_chan_spec *template,
+					  int max_chan_id,
+					  struct iio_chan_spec **cs);
+
+#endif /* _INDUSTRIAL_IO_ADC_HELPERS_H_ */
-- 
2.48.1


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[PATCH v6 05/10] iio: adc: sun20i-gpadc: Use adc-helpers

[Matti Vaittinen]

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The new devm_iio_adc_device_alloc_chaninfo() -helper is intended to help
drivers avoid open-coding the for_each_node -loop for getting the
channel IDs. The helper provides standard way to detect the ADC channel
nodes (by the node name), and a standard way to convert the "reg"
-properties to channel identification numbers, used in the struct
iio_chan_spec. Furthermore, the helper can optionally check the found
channel IDs are smaller than given maximum. This is useful for callers
which later use the IDs for example for indexing a channel data array.

The original driver treated all found child nodes as channel nodes. The
new helper requires channel nodes to be named channel[@N]. This should
help avoid problems with devices which may contain also other but ADC
child nodes. Quick grep from arch/* with the sun20i-gpadc's compatible
string didn't reveal any in-tree .dts with channel nodes named
otherwise. Also, same grep shows all the in-tree .dts seem to have
channel IDs between 0..num of channels.

Use the new helper.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---
Revision history:
v5 => v6:
 - Commit message typofix
v4 => v5:
 - Drop the diff-channel stuff from the commit message
v3 => v4:
 - Adapt to 'drop diff-channel support' changes to ADC-helpers
 - select ADC helpers in the Kconfig
v2 => v3:
 - New patch

I picked the sun20i-gpadc in this series because it has a straightforward
approach for populating the struct iio_chan_spec. Everything else except
the .channel can use 'template'-data.

This makes the sun20i-gpadc well suited to be an example user of this new
helper. I hope this patch helps to evaluate whether these helpers are worth
the hassle.

The change is compile tested only!! Testing before applying is highly
appreciated (as always!). Also, even though I tried to audit the dts
files for the reg-properties in the channel nodes, use of references
didn't make it easy. I can't guarantee I didn't miss anything.
---
 drivers/iio/adc/Kconfig            |  1 +
 drivers/iio/adc/sun20i-gpadc-iio.c | 38 ++++++++++++------------------
 2 files changed, 16 insertions(+), 23 deletions(-)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index e4933de0c366..0993008a1586 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -1357,6 +1357,7 @@ config SUN4I_GPADC
 config SUN20I_GPADC
 	tristate "Allwinner D1/T113s/T507/R329 and similar GPADCs driver"
 	depends on ARCH_SUNXI || COMPILE_TEST
+	select IIO_ADC_HELPER
 	help
 	  Say yes here to build support for Allwinner (D1, T113, T507 and R329)
 	  SoCs GPADC. This ADC provides up to 16 channels.
diff --git a/drivers/iio/adc/sun20i-gpadc-iio.c b/drivers/iio/adc/sun20i-gpadc-iio.c
index 136b8d9c294f..bf1db2a3de9b 100644
--- a/drivers/iio/adc/sun20i-gpadc-iio.c
+++ b/drivers/iio/adc/sun20i-gpadc-iio.c
@@ -15,6 +15,7 @@
 #include <linux/property.h>
 #include <linux/reset.h>
 
+#include <linux/iio/adc-helpers.h>
 #include <linux/iio/iio.h>
 
 #define SUN20I_GPADC_DRIVER_NAME	"sun20i-gpadc"
@@ -149,37 +150,27 @@ static void sun20i_gpadc_reset_assert(void *data)
 	reset_control_assert(rst);
 }
 
+static const struct iio_chan_spec sun20i_gpadc_chan_template = {
+	.type = IIO_VOLTAGE,
+	.indexed = 1,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),
+};
+
 static int sun20i_gpadc_alloc_channels(struct iio_dev *indio_dev,
 				       struct device *dev)
 {
-	unsigned int channel;
-	int num_channels, i, ret;
+	int num_channels;
 	struct iio_chan_spec *channels;
 
-	num_channels = device_get_child_node_count(dev);
+	num_channels = devm_iio_adc_device_alloc_chaninfo_se(dev,
+				&sun20i_gpadc_chan_template, -1, &channels);
+	if (num_channels < 0)
+		return num_channels;
+
 	if (num_channels == 0)
 		return dev_err_probe(dev, -ENODEV, "no channel children\n");
 
-	channels = devm_kcalloc(dev, num_channels, sizeof(*channels),
-				GFP_KERNEL);
-	if (!channels)
-		return -ENOMEM;
-
-	i = 0;
-	device_for_each_child_node_scoped(dev, node) {
-		ret = fwnode_property_read_u32(node, "reg", &channel);
-		if (ret)
-			return dev_err_probe(dev, ret, "invalid channel number\n");
-
-		channels[i].type = IIO_VOLTAGE;
-		channels[i].indexed = 1;
-		channels[i].channel = channel;
-		channels[i].info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
-		channels[i].info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
-
-		i++;
-	}
-
 	indio_dev->channels = channels;
 	indio_dev->num_channels = num_channels;
 
@@ -271,3 +262,4 @@ module_platform_driver(sun20i_gpadc_driver);
 MODULE_DESCRIPTION("ADC driver for sunxi platforms");
 MODULE_AUTHOR("Maksim Kiselev <bigunclemax@gmail.com>");
 MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("IIO_DRIVER");
-- 
2.48.1


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[PATCH v6 07/10] MAINTAINERS: Add IIO ADC helpers

[Matti Vaittinen]

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Add undersigned as a maintainer for the IIO ADC helpers.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
---
Revision history:
v2 =>
 - No changes
RFC v1 => v2:
 - New patch
---
 MAINTAINERS | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 8e0736dc2ee0..5b96fb864227 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11208,6 +11208,13 @@ L:	linux-media@vger.kernel.org
 S:	Maintained
 F:	drivers/media/rc/iguanair.c
 
+IIO ADC HELPERS
+M:	Matti Vaittinen <mazziesaccount@gmail.com>
+L:	linux-iio@vger.kernel.org
+S:	Maintained
+F:	drivers/iio/adc/industrialio-adc.c
+F:	include/linux/iio/adc-helpers.h
+
 IIO BACKEND FRAMEWORK
 M:	Nuno Sa <nuno.sa@analog.com>
 R:	Olivier Moysan <olivier.moysan@foss.st.com>
-- 
2.48.1


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Re: [PATCH v6 05/10] iio: adc: sun20i-gpadc: Use adc-helpers

[Jonathan Cameron]

On Mon, 10 Mar 2025 14:56:35 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> The new devm_iio_adc_device_alloc_chaninfo() -helper is intended to help
here as well.  I'd have just fixed these up if applying but seeing as
you seem to be heading for a v7, good to tidy these up in that!

Re: [PATCH v6 00/10] Support ROHM BD79124 ADC

[Jonathan Cameron]

On Mon, 10 Mar 2025 14:53:50 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> Support ROHM BD79124 ADC.
> 
> This series adds also couple of IIO ADC helper functions for parsing the
> channel information from the device tree. There are also new helpers
> included for iterating and counting firmware child nodes with a specific
> name.
> 
> Series does also convert couple of drivers to use these helpers. The
> rzg2l_adc and the sun20i-gpadc are converted to use the new ADC helper.
> 
> The gianfar driver under net and the thp7312 under media/i2c are added as
> first users of the newly added "named child node" -helpers.
> 
> There has been some discussion about how useful these ADC helpers are,
> and whether they should support also differential and single ended channel
> configurations. This version does not include support for those - with the
> benefit of reduced complexity and easier to use API.
> 
> NOTE: Patches 4,5,9 and 10 are untested as I lack of relevant HW.
> They have been compile tested only.
This probably wants an update.  Also, 00/10? There are only 8 that I can see.

Jonathan

Re: [PATCH v6 00/10] Support ROHM BD79124 ADC

[Matti Vaittinen]

On 10/03/2025 22:27, Jonathan Cameron wrote:
> On Mon, 10 Mar 2025 14:53:50 +0200
> Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> 
>> Support ROHM BD79124 ADC.
>>
>> This series adds also couple of IIO ADC helper functions for parsing the
>> channel information from the device tree. There are also new helpers
>> included for iterating and counting firmware child nodes with a specific
>> name.
>>
>> Series does also convert couple of drivers to use these helpers. The
>> rzg2l_adc and the sun20i-gpadc are converted to use the new ADC helper.
>>
>> The gianfar driver under net and the thp7312 under media/i2c are added as
>> first users of the newly added "named child node" -helpers.
>>
>> There has been some discussion about how useful these ADC helpers are,
>> and whether they should support also differential and single ended channel
>> configurations. This version does not include support for those - with the
>> benefit of reduced complexity and easier to use API.
>>
>> NOTE: Patches 4,5,9 and 10 are untested as I lack of relevant HW.
>> They have been compile tested only.
> This probably wants an update.  Also, 00/10? There are only 8 that I can see.

That's odd.
There should be 10 in total. And the 4, 5, 9 and 10 was updated.

9/10:
https://lore.kernel.org/all/1c4b9b4ceb1995bce76a0ddef0e04ad0d1d81190.1741610847.git.mazziesaccount@gmail.com/

10/10:
https://lore.kernel.org/all/ab79cf4415d21ff2854fee4f4189fac555c30b7a.1741610847.git.mazziesaccount@gmail.com/

Perhaps it's because of the "net-next" in subject?

Yours,
	-- Matti

Re: [PATCH v6 00/10] Support ROHM BD79124 ADC

[Jonathan Cameron]

On Tue, 11 Mar 2025 07:49:35 +0200
Matti Vaittinen <mazziesaccount@gmail.com> wrote:

> On 10/03/2025 22:27, Jonathan Cameron wrote:
> > On Mon, 10 Mar 2025 14:53:50 +0200
> > Matti Vaittinen <mazziesaccount@gmail.com> wrote:
> >   
> >> Support ROHM BD79124 ADC.
> >>
> >> This series adds also couple of IIO ADC helper functions for parsing the
> >> channel information from the device tree. There are also new helpers
> >> included for iterating and counting firmware child nodes with a specific
> >> name.
> >>
> >> Series does also convert couple of drivers to use these helpers. The
> >> rzg2l_adc and the sun20i-gpadc are converted to use the new ADC helper.
> >>
> >> The gianfar driver under net and the thp7312 under media/i2c are added as
> >> first users of the newly added "named child node" -helpers.
> >>
> >> There has been some discussion about how useful these ADC helpers are,
> >> and whether they should support also differential and single ended channel
> >> configurations. This version does not include support for those - with the
> >> benefit of reduced complexity and easier to use API.
> >>
> >> NOTE: Patches 4,5,9 and 10 are untested as I lack of relevant HW.
> >> They have been compile tested only.  
> > This probably wants an update.  Also, 00/10? There are only 8 that I can see.  
> 
> That's odd.
> There should be 10 in total. And the 4, 5, 9 and 10 was updated.
> 
> 9/10:
> https://lore.kernel.org/all/1c4b9b4ceb1995bce76a0ddef0e04ad0d1d81190.1741610847.git.mazziesaccount@gmail.com/
> 
> 10/10:
> https://lore.kernel.org/all/ab79cf4415d21ff2854fee4f4189fac555c30b7a.1741610847.git.mazziesaccount@gmail.com/
> 
> Perhaps it's because of the "net-next" in subject?
> 
Nope. My filters broke the series up into different directories.

Thanks,

Jonathan

> Yours,
> 	-- Matti