linux-kernel - [PATCH v3 7/9] iio: adc: sun20i-gpadc: Use adc-helpers

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Message-ID: <21b9af362b64a1d9c2a13cc46242dd6955996c46.1739967040.git.mazziesaccount@gmail.com>
Date: Wed, 19 Feb 2025 14:31:51 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Chen-Yu Tsai <wens@...e.org>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Samuel Holland <samuel@...lland.org>,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	Nuno Sa <nuno.sa@...log.com>, David Lechner <dlechner@...libre.com>,
	Javier Carrasco <javier.carrasco.cruz@...il.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: [PATCH v3 7/9] iio: adc: sun20i-gpadc: Use adc-helpers

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",
"diff-channels", "single-channel" and the "common-mode-channel" to
channel identification numbers used in the struct iio_chan_spec.
Furthermore, the helper checks the ID is in range of 0 ... num-channels.

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
othervice. 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@...il.com>

---
Revision history:
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/sun20i-gpadc-iio.c | 42 ++++++++++++++----------------
 1 file changed, 19 insertions(+), 23 deletions(-)

diff --git a/drivers/iio/adc/sun20i-gpadc-iio.c b/drivers/iio/adc/sun20i-gpadc-iio.c
index 136b8d9c294f..36d48d95f029 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 +150,32 @@ 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 const struct iio_adc_props sun20i_gpadc_chan_props = {
+	.required = IIO_ADC_CHAN_PROP_TYPE_REG,
+};
+
 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(dev,
+					&sun20i_gpadc_chan_template, &channels,
+					&sun20i_gpadc_chan_props);
+	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;
 
-- 
2.48.1


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