[PATCH 13/15] iio: core: Add support for cyclic buffers

[Paul Cercueil <paul@crapouillou.net>]

Introduce a new flag IIO_BUFFER_DMABUF_CYCLIC in the "flags" field of
the iio_dmabuf uapi structure.

When set, the DMABUF enqueued with the enqueue ioctl will be endlessly
repeated on the TX output, until the buffer is disabled.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 drivers/iio/industrialio-buffer.c | 5 +++++
 include/uapi/linux/iio/buffer.h   | 3 ++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index 30910e6c2346..41bc51c88002 100644
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -1600,6 +1600,11 @@ static int iio_buffer_enqueue_dmabuf(struct iio_buffer *buffer,
 	if (dmabuf.flags & ~IIO_BUFFER_DMABUF_SUPPORTED_FLAGS)
 		return -EINVAL;
 
+	/* Cyclic flag is only supported on output buffers */
+	if ((dmabuf.flags & IIO_BUFFER_DMABUF_CYCLIC) &&
+	    buffer->direction != IIO_BUFFER_DIRECTION_OUT)
+		return -EINVAL;
+
 	return buffer->access->enqueue_dmabuf(buffer, &dmabuf);
 }
 
diff --git a/include/uapi/linux/iio/buffer.h b/include/uapi/linux/iio/buffer.h
index e4621b926262..2d541d038c02 100644
--- a/include/uapi/linux/iio/buffer.h
+++ b/include/uapi/linux/iio/buffer.h
@@ -7,7 +7,8 @@
 
 #include <linux/types.h>
 
-#define IIO_BUFFER_DMABUF_SUPPORTED_FLAGS	0x00000000
+#define IIO_BUFFER_DMABUF_CYCLIC		(1 << 0)
+#define IIO_BUFFER_DMABUF_SUPPORTED_FLAGS	0x00000001
 
 /**
  * struct iio_dmabuf_alloc_req - Descriptor for allocating IIO DMABUFs
-- 
2.33.0