[PATCH v3 3/7] iio: core: Match iio_device_claim_*() semantics and implementation

Kurt Borja
2026-01-06T08:07:17Z

Implement iio_device_claim_buffer_mode() fully inline with the use of
__iio_dev_mode_lock(), which takes care of sparse annotations.

To completely match iio_device_claim_direct() semantics, we need to
also change iio_device_claim_buffer_mode() return semantics to usual
true/false conditional lock semantics.

Additionally, to avoid silently breaking out-of-tree drivers, rename
iio_device_claim_buffer_mode() to iio_device_claim_try_buffer_mode().

Signed-off-by: Kurt Borja <kuurtb@gmail.com>
---
drivers/iio/adc/ade9000.c | 2 +-
.../common/cros_ec_sensors/cros_ec_sensors_core.c | 5 +--
drivers/iio/health/max30100.c | 8 +----
drivers/iio/health/max30102.c | 2 +-
drivers/iio/industrialio-core.c | 42 +---------------------
drivers/iio/light/opt4060.c | 2 +-
include/linux/iio/iio.h | 35 ++++++++++++++++--
7 files changed, 39 insertions(+), 57 deletions(-)

diff --git a/drivers/iio/adc/ade9000.c b/drivers/iio/adc/ade9000.c
index 2de8a718d62a..db085dc5e526 100644
--- a/drivers/iio/adc/ade9000.c
+++ b/drivers/iio/adc/ade9000.c
@@ -964,7 +964,7 @@ static irqreturn_t ade9000_dready_thread(int irq, void *data)
struct iio_dev *indio_dev = data;

/* Handle data ready interrupt from C4/EVENT/DREADY pin */
- if (!iio_device_claim_buffer_mode(indio_dev)) {
+ if (iio_device_try_claim_buffer_mode(indio_dev)) {
ade9000_iio_push_buffer(indio_dev);
iio_device_release_buffer_mode(indio_dev);
}
diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
index 9ac80e4b7d75..ef53066b1735 100644
--- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
+++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c
@@ -188,11 +188,8 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev,
/*
* Ignore samples if the buffer is not set: it is needed if the ODR is
* set but the buffer is not enabled yet.
- *
- * Note: iio_device_claim_buffer_mode() returns -EBUSY if the buffer
- * is not enabled.
*/
- if (iio_device_claim_buffer_mode(indio_dev) < 0)
+ if (!iio_device_try_claim_buffer_mode(indio_dev))
return 0;

out = (s16 *)st->samples;
diff --git a/drivers/iio/health/max30100.c b/drivers/iio/health/max30100.c
index 3d441013893c..7dfdb5eb305e 100644
--- a/drivers/iio/health/max30100.c
+++ b/drivers/iio/health/max30100.c
@@ -417,13 +417,7 @@ static int max30100_read_raw(struct iio_dev *indio_dev,
* Temperature reading can only be acquired while engine
* is running
*/
- if (iio_device_claim_buffer_mode(indio_dev)) {
- /*
- * Replacing -EBUSY or other error code
- * returned by iio_device_claim_buffer_mode()
- * because user space may rely on the current
- * one.
- */
+ if (!iio_device_try_claim_buffer_mode(indio_dev)) {
ret = -EAGAIN;
} else {
ret = max30100_get_temp(data, val);
diff --git a/drivers/iio/health/max30102.c b/drivers/iio/health/max30102.c
index a48c0881a4c7..6918fcb5de2b 100644
--- a/drivers/iio/health/max30102.c
+++ b/drivers/iio/health/max30102.c
@@ -476,7 +476,7 @@ static int max30102_read_raw(struct iio_dev *indio_dev,
* shutdown; leave shutdown briefly when buffer not running
*/
any_mode_retry:
- if (iio_device_claim_buffer_mode(indio_dev)) {
+ if (!iio_device_try_claim_buffer_mode(indio_dev)) {
/*
* This one is a *bit* hacky. If we cannot claim buffer
* mode, then try direct mode so that we make sure
diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 550d100d9cfa..52a16ce87e02 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -2183,7 +2183,7 @@ EXPORT_SYMBOL_GPL(__devm_iio_device_register);
*
* There are very few cases where a driver actually needs to lock the current
* mode unconditionally. It's recommended to use iio_device_claim_direct() or
- * iio_device_claim_buffer_mode() pairs or related helpers instead.
+ * iio_device_try_claim_buffer_mode() pairs or related helpers instead.
*/
void __iio_dev_mode_lock(struct iio_dev *indio_dev)
{
@@ -2201,46 +2201,6 @@ void __iio_dev_mode_unlock(struct iio_dev *indio_dev)
}
EXPORT_SYMBOL_GPL(__iio_dev_mode_unlock);

-/**
- * iio_device_claim_buffer_mode - Keep device in buffer mode
- * @indio_dev: the iio_dev associated with the device
- *
- * If the device is in buffer mode it is guaranteed to stay
- * that way until iio_device_release_buffer_mode() is called.
- *
- * Use with iio_device_release_buffer_mode().
- *
- * Returns: 0 on success, -EBUSY on failure.
- */
-int iio_device_claim_buffer_mode(struct iio_dev *indio_dev)
-{
- struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
-
- mutex_lock(&iio_dev_opaque->mlock);
-
- if (iio_buffer_enabled(indio_dev))
- return 0;
-
- mutex_unlock(&iio_dev_opaque->mlock);
- return -EBUSY;
-}
-EXPORT_SYMBOL_GPL(iio_device_claim_buffer_mode);
-
-/**
- * iio_device_release_buffer_mode - releases claim on buffer mode
- * @indio_dev: the iio_dev associated with the device
- *
- * Release the claim. Device is no longer guaranteed to stay
- * in buffer mode.
- *
- * Use with iio_device_claim_buffer_mode().
- */
-void iio_device_release_buffer_mode(struct iio_dev *indio_dev)
-{
- mutex_unlock(&to_iio_dev_opaque(indio_dev)->mlock);
-}
-EXPORT_SYMBOL_GPL(iio_device_release_buffer_mode);
-
/**
* iio_device_get_current_mode() - helper function providing read-only access to
* the opaque @currentmode variable
diff --git a/drivers/iio/light/opt4060.c b/drivers/iio/light/opt4060.c
index 981c704e7df5..8c4a1f562a83 100644
--- a/drivers/iio/light/opt4060.c
+++ b/drivers/iio/light/opt4060.c
@@ -304,7 +304,7 @@ static int opt4060_set_driver_state(struct iio_dev *indio_dev,
struct opt4060_chip *chip = iio_priv(indio_dev);
int ret = 0;
any_mode_retry:
- if (iio_device_claim_buffer_mode(indio_dev)) {
+ if (!iio_device_try_claim_buffer_mode(indio_dev)) {
/*
* This one is a *bit* hacky. If we cannot claim buffer mode,
* then try direct mode so that we make sure things cannot
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 3cf340208694..d8af0456f966 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -706,8 +706,39 @@ static inline bool iio_device_claim_direct(struct iio_dev *indio_dev)
*/
#define iio_device_release_direct(indio_dev) __iio_dev_mode_unlock(indio_dev)

-int iio_device_claim_buffer_mode(struct iio_dev *indio_dev);
-void iio_device_release_buffer_mode(struct iio_dev *indio_dev);
+/**
+ * iio_device_try_claim_buffer_mode - Keep device in buffer mode
+ * @indio_dev: the iio_dev associated with the device
+ *
+ * If the device is in buffer mode it is guaranteed to stay
+ * that way until iio_device_release_buffer_mode() is called.
+ *
+ * Use with iio_device_release_buffer_mode().
+ *
+ * Returns: true on success, false on failure.
+ */
+static inline bool iio_device_try_claim_buffer_mode(struct iio_dev *indio_dev)
+{
+ __iio_dev_mode_lock(indio_dev);
+
+ if (!iio_buffer_enabled(indio_dev)) {
+ __iio_dev_mode_unlock(indio_dev);
+ return false;
+ }
+
+ return true;
+}
+
+/**
+ * iio_device_release_buffer_mode - releases claim on buffer mode
+ * @indio_dev: the iio_dev associated with the device
+ *
+ * Release the claim. Device is no longer guaranteed to stay
+ * in buffer mode.
+ *
+ * Use with iio_device_try_claim_buffer_mode().
+ */
+#define iio_device_release_buffer_mode(indio_dev) __iio_dev_mode_unlock(indio_dev)

extern const struct bus_type iio_bus_type;

--
2.52.0