linux-kernel - [PATCH v2 2/4] iio: backend: add devm_iio_backend_get_by

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Message-ID: <550323d752213f177b7673bdd42e667f1d2228cb.1770393792.git.antoniu.miclaus@analog.com>
Date: Fri, 6 Feb 2026 18:07:14 +0200
From: Antoniu Miclaus <antoniu.miclaus@...log.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>,
        Lars-Peter Clausen
	<lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        "Jonathan Cameron" <jic23@...nel.org>,
        David Lechner <dlechner@...libre.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Andy Shevchenko
	<andy@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Olivier Moysan
	<olivier.moysan@...s.st.com>,
        Mark Brown <broonie@...nel.org>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>
Subject: [PATCH v2 2/4] iio: backend: add devm_iio_backend_get_by_index()

Add a new function to get an IIO backend by its index in the
io-backends device tree property. This is useful for multi-channel
devices that have multiple backends, where looking up by index is
more straightforward than using named backends.

The new function directly uses the index to find the backend reference
in the io-backends property, avoiding the need for io-backend-names.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
---
 drivers/iio/industrialio-backend.c | 51 ++++++++++++++++++++++++++++++
 include/linux/iio/backend.h        |  2 ++
 2 files changed, 53 insertions(+)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 447b694d6d5f..3b692d48481e 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -1008,6 +1008,57 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
 }
 EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get, "IIO_BACKEND");
 
+static struct iio_backend *
+__devm_iio_backend_fwnode_get_by_index(struct device *dev,
+				       struct fwnode_handle *fwnode,
+				       unsigned int index)
+{
+	struct fwnode_handle *fwnode_back;
+	struct iio_backend *back;
+	int ret;
+
+	fwnode_back = fwnode_find_reference(fwnode, "io-backends", index);
+	if (IS_ERR(fwnode_back))
+		return dev_err_cast_probe(dev, fwnode_back,
+					  "Cannot get Firmware reference\n");
+
+	guard(mutex)(&iio_back_lock);
+	list_for_each_entry(back, &iio_back_list, entry) {
+		if (!device_match_fwnode(back->dev, fwnode_back))
+			continue;
+
+		fwnode_handle_put(fwnode_back);
+		ret = __devm_iio_backend_get(dev, back);
+		if (ret)
+			return ERR_PTR(ret);
+
+		back->idx = index;
+
+		return back;
+	}
+
+	fwnode_handle_put(fwnode_back);
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+/**
+ * devm_iio_backend_get_by_index - Device managed backend device get by index
+ * @dev: Consumer device for the backend
+ * @index: Index of the backend in the io-backends property
+ *
+ * Get's the backend at @index associated with @dev.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
+						  unsigned int index)
+{
+	return __devm_iio_backend_fwnode_get_by_index(dev, dev_fwnode(dev),
+						      index);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get_by_index, "IIO_BACKEND");
+
 /**
  * devm_iio_backend_fwnode_get - Device managed backend firmware node get
  * @dev: Consumer device for the backend
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 7f815f3fed6a..8f18df0ca896 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -237,6 +237,8 @@ int iio_backend_extend_chan_spec(struct iio_backend *back,
 				 struct iio_chan_spec *chan);
 void *iio_backend_get_priv(const struct iio_backend *conv);
 struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name);
+struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
+						  unsigned int index);
 struct iio_backend *devm_iio_backend_fwnode_get(struct device *dev,
 						const char *name,
 						struct fwnode_handle *fwnode);
-- 
2.43.0