[PATCH v4 1/7] iio: core: Add and export __iio_dev_mode_lock()

[Kurt Borja <kuurtb@gmail.com>]

Add unconditional wrappers around the internal IIO mode lock.

As mentioned in the documentation, this is not meant to be used by
drivers, instead this will aid in the eventual addition of cleanup
classes around conditional locks.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Kurt Borja <kuurtb@gmail.com>
---
 drivers/iio/industrialio-core.c | 30 ++++++++++++++++++++++++++++++
 include/linux/iio/iio.h         |  3 +++
 2 files changed, 33 insertions(+)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index f69deefcfb6f..9693a6bb3917 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -2171,6 +2171,36 @@ int __devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev,
 }
 EXPORT_SYMBOL_GPL(__devm_iio_device_register);
 
+/**
+ * __iio_dev_mode_lock - Locks the current IIO device mode
+ * @indio_dev: the iio_dev associated with the device
+ *
+ * If the device is either in direct or buffer mode, it's guaranteed to stay
+ * that way until __iio_dev_mode_unlock() is called.
+ *
+ * This function is not meant to be used directly by drivers to protect internal
+ * state; a driver should have it's own mechanisms for that matter.
+ *
+ * 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.
+ */
+void __iio_dev_mode_lock(struct iio_dev *indio_dev)
+{
+	mutex_lock(&to_iio_dev_opaque(indio_dev)->mlock);
+}
+EXPORT_SYMBOL_GPL(__iio_dev_mode_lock);
+
+/**
+ * __iio_dev_mode_unlock - Unlocks the current IIO device mode
+ * @indio_dev: the iio_dev associated with the device
+ */
+void __iio_dev_mode_unlock(struct iio_dev *indio_dev)
+{
+	mutex_unlock(&to_iio_dev_opaque(indio_dev)->mlock);
+}
+EXPORT_SYMBOL_GPL(__iio_dev_mode_unlock);
+
 /**
  * __iio_device_claim_direct - Keep device in direct mode
  * @indio_dev:	the iio_dev associated with the device
diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
index 872ebdf0dd77..aecda887d833 100644
--- a/include/linux/iio/iio.h
+++ b/include/linux/iio/iio.h
@@ -661,6 +661,9 @@ void iio_device_unregister(struct iio_dev *indio_dev);
 int __devm_iio_device_register(struct device *dev, struct iio_dev *indio_dev,
 			       struct module *this_mod);
 int iio_push_event(struct iio_dev *indio_dev, u64 ev_code, s64 timestamp);
+
+void __iio_dev_mode_lock(struct iio_dev *indio_dev) __acquires(indio_dev);
+void __iio_dev_mode_unlock(struct iio_dev *indio_dev) __releases(indio_dev);
 bool __iio_device_claim_direct(struct iio_dev *indio_dev);
 void __iio_device_release_direct(struct iio_dev *indio_dev);
 

-- 
2.52.0