This new API is used in `iio_poll_func_register()` to handle the case
where the trigger writes a timestamp directly into the consumer (i.e. early_timestamp == true).

Signed-off-by: Gyeyoung Baek <gye976@gmail.com>
---
 drivers/iio/industrialio-trigger.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/iio/industrialio-trigger.c b/drivers/iio/industrialio-trigger.c
index d6b0e1ec4153..f394933b9d0a 100644
--- a/drivers/iio/industrialio-trigger.c
+++ b/drivers/iio/industrialio-trigger.c
@@ -288,6 +288,15 @@ static void iio_trigger_put_irq(struct iio_trigger *trig, int irq)
 	clear_bit(irq - trig->subirq_base, trig->pool);
 }
 
+static int iio_trigger_attach_timestamp(struct iio_trigger *trig,
+					  struct iio_poll_func *pf)
+{
+	/* RFC */
+	trig->consumer_pf[pf->irq - trig->subirq_base] = pf;
+
+	return 0;
+}
+
 static int iio_poll_func_register(struct iio_poll_func *pf,
 				  struct iio_trigger *trig)
 {
@@ -302,6 +311,16 @@ static int iio_poll_func_register(struct iio_poll_func *pf,
 	if (!pf->timestamp_enabled)
 		goto out_request_irq;
 
+	/*
+	 * The trigger supports grabbing timestamp.
+	 * Just request raw irq handler.
+	 */
+	if (trig->early_timestamp) {
+		ret = iio_trigger_attach_timestamp(trig, pf);
+		pf->timestamp_type = IIO_TIMESTAMP_TYPE_TRIGGER;
+		goto out_request_irq;
+	}
+
 	if (trig->trig_type & IIO_TRIG_TYPE_POLL_NESTED) {
 		bottomhalf = iio_pollfunc_bottom_half_wrapper;
 		pf->timestamp_type = IIO_TIMESTAMP_TYPE_CONSUMER_BOTTOM_HALF;
@@ -395,6 +414,9 @@ int iio_trigger_detach_poll_func(struct iio_trigger *trig,
 	module_put(iio_dev_opaque->driver_module);
 	pf->irq = 0;
 
+	/* RFC */
+	trig->consumer_pf[pf->irq - trig->subirq_base] = NULL;
+
 	return ret;
 }
 

-- 
2.43.0