[PATCH v3 2/4] iio: industrialio-backend: support backend capabilities

Tomas Melin
2026-01-14T10:46:40Z

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@vaisala.com>
---
drivers/iio/industrialio-backend.c | 17 +++++++++++++++++
include/linux/iio/backend.h | 17 +++++++++++++++++
2 files changed, 34 insertions(+)

diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 447b694d6d5f72dc6f018b1697fdb88e555bd61e..0a98fdd5df9db6cc233af819ac5243ba8cd5266f 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -56,6 +56,7 @@ struct iio_backend {
void *priv;
const char *name;
unsigned int cached_reg_addr;
+ u32 caps;
/*
* This index is relative to the frontend. Meaning that for
* frontends with multiple backends, this will be the index of this
@@ -774,6 +775,21 @@ int iio_backend_extend_chan_spec(struct iio_backend *back,
}
EXPORT_SYMBOL_NS_GPL(iio_backend_extend_chan_spec, "IIO_BACKEND");

+/**
+ * iio_backend_has_caps - Check if backend has specific capabilities
+ * @back: Backend device
+ * @caps: Capabilities to check
+ *
+ * RETURNS:
+ * Non-zero value if backend has all the requested capabilities,
+ * 0 otherwise.
+ */
+int iio_backend_has_caps(struct iio_backend *back, u32 caps)
+{
+ return back->caps & caps;
+}
+EXPORT_SYMBOL_NS_GPL(iio_backend_has_caps, "IIO_BACKEND");
+
static void iio_backend_release(void *arg)
{
struct iio_backend *back = arg;
@@ -1114,6 +1130,7 @@ int devm_iio_backend_register(struct device *dev,

back->ops = info->ops;
back->name = info->name;
+ back->caps = info->caps;
back->owner = dev->driver->owner;
back->dev = dev;
back->priv = priv;
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 7f815f3fed6ae34c65ffc579d5101020fc9bd336..8a0df8e980e910ac2d5398275963dc5adf077c8a 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -84,6 +84,20 @@ enum iio_backend_filter_type {
IIO_BACKEND_FILTER_TYPE_MAX
};

+/**
+ * enum iio_backend_capabilities - Backend capabilities
+ * Backend capabilities can be used by frontends to check if a given
+ * functionality is supported by the backend. Capabilities are loosely
+ * coupled with operations, meaning that a capability requires certain
+ * operations to be implemented by the backend.
+ * @IIO_BACKEND_CAP_CALIBRATION: Backend supports calibration. Needs at least
+ * iodelay_set(), test_pattern_set() data_sample_trigger(), chan_status()
+ * and data_format_set() operations implemented.
+ */
+enum iio_backend_capabilities {
+ IIO_BACKEND_CAP_CALIBRATION = BIT(0),
+};
+
/**
* struct iio_backend_ops - operations structure for an iio_backend
* @enable: Enable backend.
@@ -179,10 +193,12 @@ struct iio_backend_ops {
* struct iio_backend_info - info structure for an iio_backend
* @name: Backend name.
* @ops: Backend operations.
+ * @caps: Backend capabilities. @see iio_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 +251,7 @@ 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_has_caps(struct iio_backend *back, u32 caps);
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