iio: Add support for indicating fixed watermarks

For buffers which have a fixed wake-up watermark the watermark attribute
should be read-only. Add a new FIXED_WATERMARK flag to the
struct iio_buffer_access_funcs, which can be set by a buffer
implementation.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
index 1600c55828e0..4d99a53d1fe7 100644
--- a/include/linux/iio/buffer.h
+++ b/include/linux/iio/buffer.h
@@ -18,6 +18,12 @@
 struct iio_buffer;
 
 /**
+ * INDIO_BUFFER_FLAG_FIXED_WATERMARK - Watermark level of the buffer can not be
+ *   configured. It has a fixed value which will be buffer specific.
+ */
+#define INDIO_BUFFER_FLAG_FIXED_WATERMARK BIT(0)
+
+/**
  * struct iio_buffer_access_funcs - access functions for buffers.
  * @store_to:           actually store stuff to the buffer
  * @read_first_n:       try to get a specified number of bytes (must exist)
@@ -30,6 +36,7 @@ struct iio_buffer;
  * @release:            called when the last reference to the buffer is dropped,
  *                      should free all resources allocated by the buffer.
  * @modes:              Supported operating modes by this buffer type
+ * @flags:              A bitmask combination of INDIO_BUFFER_FLAG_*
  *
  * The purpose of this structure is to make the buffer element
  * modular as event for a given driver, different usecases may require
@@ -54,6 +61,7 @@ struct iio_buffer_access_funcs {
         void (*release)(struct iio_buffer *buffer);
 
         unsigned int modes;
+        unsigned int flags;
 };
 
 /**