iio: core: Match iio_device_claim_*() semantics and implementation

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().

Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Kurt Borja <kuurtb@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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);
 	}

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;

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);

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

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

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

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;