iio: expose iio_device_set_clock

Some IIO devices may want to override the default (realtime) to another
clock source by default.

It can beneficial when timestamps coming from the hardware or underlying
drivers are already in that format.

It can always be overridden by attribute current_timestamp_clock.
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

drivers/iio/industrialio-core.c

@@ -189,7 +189,12 @@ ssize_t iio_read_const_attr(struct device *dev,
 }
 EXPORT_SYMBOL(iio_read_const_attr);
 
-static int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
+/**
+ * iio_device_set_clock() - Set current timestamping clock for the device
+ * @indio_dev: IIO device structure containing the device
+ * @clock_id: timestamping clock posix identifier to set.
+ */
+int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
 {
 	int ret;
 	const struct iio_event_interface *ev_int = indio_dev->event_interface;
@@ -207,6 +212,7 @@ static int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id)
 
 	return 0;
 }
+EXPORT_SYMBOL(iio_device_set_clock);
 
 /**
  * iio_get_time_ns() - utility function to get a time stamp for events etc

include/linux/iio/iio.h

@@ -627,6 +627,8 @@ static inline clockid_t iio_device_get_clock(const struct iio_dev *indio_dev)
 	return indio_dev->clock_id;
 }
 
+int iio_device_set_clock(struct iio_dev *indio_dev, clockid_t clock_id);
+
 /**
  * dev_to_iio_dev() - Get IIO device struct from a device struct
  * @dev: 		The device embedded in the IIO device