iio: Wakeup poll and blocking reads when the device is unregistered

Once the device has been unregistered there won't be any new data no matter how
long a userspace application waits, so we might as well wake them up and let
them know.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 6c7a9c509399..5a46c57a038b 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -20,6 +20,7 @@
 #include <linux/cdev.h>
 #include <linux/slab.h>
 #include <linux/poll.h>
+#include <linux/sched.h>
 
 #include <linux/iio/iio.h>
 #include "iio_core.h"
@@ -75,6 +76,21 @@ unsigned int iio_buffer_poll(struct file *filp,
 	return 0;
 }
 
+/**
+ * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
+ * @indio_dev: The IIO device
+ *
+ * Wakes up the event waitqueue used for poll(). Should usually
+ * be called when the device is unregistered.
+ */
+void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
+{
+	if (!indio_dev->buffer)
+		return;
+
+	wake_up(&indio_dev->buffer->pollq);
+}
+
 void iio_buffer_init(struct iio_buffer *buffer)
 {
 	INIT_LIST_HEAD(&buffer->demux_list);