iio: Add data_available callback for buffers

This patch adds a new data_available() callback to the iio_buffer_access_funcs
struct. The callback is used to indicate whether data is available in the buffer
for reading. It is meant to replace the stufftoread flag from the iio_buffer
struct. The reasoning for this is that the buffer implementation usually can
determine whether data is available rather easily based on its state, on the
other hand it can be rather tricky to update the stufftoread flag in a race free
way.

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

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 7f9152c3c4d..4dcc3a0f993 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -37,6 +37,14 @@ static bool iio_buffer_is_active(struct iio_buffer *buf)
 	return !list_empty(&buf->buffer_list);
 }
 
+static bool iio_buffer_data_available(struct iio_buffer *buf)
+{
+	if (buf->access->data_available)
+		return buf->access->data_available(buf);
+
+	return buf->stufftoread;
+}
+
 /**
  * iio_buffer_read_first_n_outer() - chrdev read for buffer access
  *
@@ -70,7 +78,7 @@ unsigned int iio_buffer_poll(struct file *filp,
 		return -ENODEV;
 
 	poll_wait(filp, &rb->pollq, wait);
-	if (rb->stufftoread)
+	if (iio_buffer_data_available(rb))
 		return POLLIN | POLLRDNORM;
 	/* need a way of knowing if there may be enough data... */
 	return 0;