linux-kernel - [PATCH v2 2/3] iio: industrialio-backend: support backend capabilities

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Message-Id: <20260113-b4-ad9467-optional-backend-v2-2-0a27e7e72f41@vaisala.com>
Date: Tue, 13 Jan 2026 12:12:48 +0000
From: Tomas Melin <tomas.melin@...sala.com>
To: Michael Hennerich <Michael.Hennerich@...log.com>, 
 Nuno Sa <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, 
 Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
 Andy Shevchenko <andy@...nel.org>, 
 Olivier Moysan <olivier.moysan@...s.st.com>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Tomas Melin <tomas.melin@...sala.com>
Subject: [PATCH v2 2/3] iio: industrialio-backend: support backend
 capabilities

Not all backends support the full set of capabilities provided by the
industrialio-backend framework. Capability bits can be used in frontends
and backends for checking for a certain feature set, or if using
related functions can be expected to fail.

Capability bits should be set by a compatible backend and provided when
registering the backend.

Signed-off-by: Tomas Melin <tomas.melin@...sala.com>
---
 drivers/iio/industrialio-backend.c | 10 ++++++++++
 include/linux/iio/backend.h        |  9 +++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 447b694d6d5f72dc6f018b1697fdb88e555bd61e..997ec743dc67e7cf420ff667af33b4f6a71a5377 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -62,6 +62,7 @@ struct iio_backend {
 	 * backend. Used for the debugfs directory name.
 	 */
 	u8 idx;
+	u32 caps;
 };
 
 /*
@@ -542,6 +543,9 @@ int devm_iio_backend_request_buffer(struct device *dev,
 	struct iio_backend_buffer_pair *pair;
 	struct iio_buffer *buffer;
 
+	if (!iio_backend_caps(back, IIO_BACKEND_CAP_BUFFERING))
+		return 0;
+
 	pair = devm_kzalloc(dev, sizeof(*pair), GFP_KERNEL);
 	if (!pair)
 		return -ENOMEM;
@@ -774,6 +778,12 @@ int iio_backend_extend_chan_spec(struct iio_backend *back,
 }
 EXPORT_SYMBOL_NS_GPL(iio_backend_extend_chan_spec, "IIO_BACKEND");
 
+int iio_backend_caps(struct iio_backend *back, u32 cap)
+{
+	return back->caps & cap;
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_caps, "IIO_BACKEND");
+
 static void iio_backend_release(void *arg)
 {
 	struct iio_backend *back = arg;
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 7f815f3fed6ae34c65ffc579d5101020fc9bd336..c020bc48cc05d6fcea00d23e471b12a29b5c0551 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -84,6 +84,12 @@ enum iio_backend_filter_type {
 	IIO_BACKEND_FILTER_TYPE_MAX
 };
 
+enum iio_backend_capabilities {
+	IIO_BACKEND_CAP_TEST_PATTERNS = BIT(0),
+	IIO_BACKEND_CAP_BUFFERING = BIT(1),
+	IIO_BACKEND_CAP_CALIBRATION = BIT(2)
+};
+
 /**
  * struct iio_backend_ops - operations structure for an iio_backend
  * @enable: Enable backend.
@@ -179,10 +185,12 @@ struct iio_backend_ops {
  * struct iio_backend_info - info structure for an iio_backend
  * @name: Backend name.
  * @ops: Backend operations.
+ * @caps: Backend capabilities.
  */
 struct iio_backend_info {
 	const char *name;
 	const struct iio_backend_ops *ops;
+	u32 caps;
 };
 
 int iio_backend_chan_enable(struct iio_backend *back, unsigned int chan);
@@ -235,6 +243,7 @@ int iio_backend_read_raw(struct iio_backend *back,
 			 long mask);
 int iio_backend_extend_chan_spec(struct iio_backend *back,
 				 struct iio_chan_spec *chan);
+int iio_backend_caps(struct iio_backend *back, u32 cap);
 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_fwnode_get(struct device *dev,

-- 
2.47.3