v4.19.13 snapshot.
diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
new file mode 100644
index 0000000..d1171db
--- /dev/null
+++ b/include/linux/iio/buffer_impl.h
@@ -0,0 +1,163 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _IIO_BUFFER_GENERIC_IMPL_H_
+#define _IIO_BUFFER_GENERIC_IMPL_H_
+#include <linux/sysfs.h>
+#include <linux/kref.h>
+
+#ifdef CONFIG_IIO_BUFFER
+
+struct iio_dev;
+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)
+ * @data_available: indicates how much data is available for reading from
+ * the buffer.
+ * @request_update: if a parameter change has been marked, update underlying
+ * storage.
+ * @set_bytes_per_datum:set number of bytes per datum
+ * @set_length: set number of datums in buffer
+ * @enable: called if the buffer is attached to a device and the
+ * device starts sampling. Calls are balanced with
+ * @disable.
+ * @disable: called if the buffer is attached to a device and the
+ * device stops sampling. Calles are balanced with @enable.
+ * @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
+ * different buffer designs (space efficiency vs speed for example).
+ *
+ * It is worth noting that a given buffer implementation may only support a
+ * small proportion of these functions. The core code 'should' cope fine with
+ * any of them not existing.
+ **/
+struct iio_buffer_access_funcs {
+ int (*store_to)(struct iio_buffer *buffer, const void *data);
+ int (*read_first_n)(struct iio_buffer *buffer,
+ size_t n,
+ char __user *buf);
+ size_t (*data_available)(struct iio_buffer *buffer);
+
+ int (*request_update)(struct iio_buffer *buffer);
+
+ int (*set_bytes_per_datum)(struct iio_buffer *buffer, size_t bpd);
+ int (*set_length)(struct iio_buffer *buffer, unsigned int length);
+
+ int (*enable)(struct iio_buffer *buffer, struct iio_dev *indio_dev);
+ int (*disable)(struct iio_buffer *buffer, struct iio_dev *indio_dev);
+
+ void (*release)(struct iio_buffer *buffer);
+
+ unsigned int modes;
+ unsigned int flags;
+};
+
+/**
+ * struct iio_buffer - general buffer structure
+ *
+ * Note that the internals of this structure should only be of interest to
+ * those writing new buffer implementations.
+ */
+struct iio_buffer {
+ /** @length: Number of datums in buffer. */
+ unsigned int length;
+
+ /** @bytes_per_datum: Size of individual datum including timestamp. */
+ size_t bytes_per_datum;
+
+ /**
+ * @access: Buffer access functions associated with the
+ * implementation.
+ */
+ const struct iio_buffer_access_funcs *access;
+
+ /** @scan_mask: Bitmask used in masking scan mode elements. */
+ long *scan_mask;
+
+ /** @demux_list: List of operations required to demux the scan. */
+ struct list_head demux_list;
+
+ /** @pollq: Wait queue to allow for polling on the buffer. */
+ wait_queue_head_t pollq;
+
+ /** @watermark: Number of datums to wait for poll/read. */
+ unsigned int watermark;
+
+ /* private: */
+ /*
+ * @scan_el_attrs: Control of scan elements if that scan mode
+ * control method is used.
+ */
+ struct attribute_group *scan_el_attrs;
+
+ /* @scan_timestamp: Does the scan mode include a timestamp. */
+ bool scan_timestamp;
+
+ /* @scan_el_dev_attr_list: List of scan element related attributes. */
+ struct list_head scan_el_dev_attr_list;
+
+ /* @buffer_group: Attributes of the buffer group. */
+ struct attribute_group buffer_group;
+
+ /*
+ * @scan_el_group: Attribute group for those attributes not
+ * created from the iio_chan_info array.
+ */
+ struct attribute_group scan_el_group;
+
+ /* @stufftoread: Flag to indicate new data. */
+ bool stufftoread;
+
+ /* @attrs: Standard attributes of the buffer. */
+ const struct attribute **attrs;
+
+ /* @demux_bounce: Buffer for doing gather from incoming scan. */
+ void *demux_bounce;
+
+ /* @buffer_list: Entry in the devices list of current buffers. */
+ struct list_head buffer_list;
+
+ /* @ref: Reference count of the buffer. */
+ struct kref ref;
+};
+
+/**
+ * iio_update_buffers() - add or remove buffer from active list
+ * @indio_dev: device to add buffer to
+ * @insert_buffer: buffer to insert
+ * @remove_buffer: buffer_to_remove
+ *
+ * Note this will tear down the all buffering and build it up again
+ */
+int iio_update_buffers(struct iio_dev *indio_dev,
+ struct iio_buffer *insert_buffer,
+ struct iio_buffer *remove_buffer);
+
+/**
+ * iio_buffer_init() - Initialize the buffer structure
+ * @buffer: buffer to be initialized
+ **/
+void iio_buffer_init(struct iio_buffer *buffer);
+
+struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer);
+void iio_buffer_put(struct iio_buffer *buffer);
+
+#else /* CONFIG_IIO_BUFFER */
+
+static inline void iio_buffer_get(struct iio_buffer *buffer) {}
+static inline void iio_buffer_put(struct iio_buffer *buffer) {}
+
+#endif /* CONFIG_IIO_BUFFER */
+#endif /* _IIO_BUFFER_GENERIC_IMPL_H_ */