remarkable-linux/include/linux/iio/buffer.h

/* The industrial I/O core - generic buffer interfaces.
 *
 * Copyright (c) 2008 Jonathan Cameron
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#ifndef _IIO_BUFFER_GENERIC_H_
#define _IIO_BUFFER_GENERIC_H_
#include <linux/sysfs.h>
#include <linux/iio/iio.h>
#include <linux/kref.h>

#ifdef CONFIG_IIO_BUFFER

struct iio_buffer;

/**
 * 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 whether data for reading from the buffer is
 *			available.
 * @request_update:	if a parameter change has been marked, update underlying
 *			storage.
 * @get_bytes_per_datum:get current bytes per datum
 * @set_bytes_per_datum:set number of bytes per datum
 * @get_length:		get number of datums in buffer
 * @set_length:		set number of datums in buffer
 * @release:		called when the last reference to the buffer is dropped,
 *			should free all resources allocated by the buffer.
 *
 * 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);
	bool (*data_available)(struct iio_buffer *buffer);

	int (*request_update)(struct iio_buffer *buffer);

	int (*get_bytes_per_datum)(struct iio_buffer *buffer);
	int (*set_bytes_per_datum)(struct iio_buffer *buffer, size_t bpd);
	int (*get_length)(struct iio_buffer *buffer);
	int (*set_length)(struct iio_buffer *buffer, int length);

	void (*release)(struct iio_buffer *buffer);
};

/**
 * struct iio_buffer - general buffer structure
 * @length:		[DEVICE] number of datums in buffer
 * @bytes_per_datum:	[DEVICE] size of individual datum including timestamp
 * @scan_el_attrs:	[DRIVER] control of scan elements if that scan mode
 *			control method is used
 * @scan_mask:		[INTERN] bitmask used in masking scan mode elements
 * @scan_timestamp:	[INTERN] does the scan mode include a timestamp
 * @access:		[DRIVER] buffer access functions associated with the
 *			implementation.
 * @scan_el_dev_attr_list:[INTERN] list of scan element related attributes.
 * @scan_el_group:	[DRIVER] attribute group for those attributes not
 *			created from the iio_chan_info array.
 * @pollq:		[INTERN] wait queue to allow for polling on the buffer.
 * @stufftoread:	[INTERN] flag to indicate new data.
 * @demux_list:		[INTERN] list of operations required to demux the scan.
 * @demux_bounce:	[INTERN] buffer for doing gather from incoming scan.
 * @buffer_list:	[INTERN] entry in the devices list of current buffers.
 * @ref:		[INTERN] reference count of the buffer.
 */
struct iio_buffer {
	int					length;
	int					bytes_per_datum;
	struct attribute_group			*scan_el_attrs;
	long					*scan_mask;
	bool					scan_timestamp;
	const struct iio_buffer_access_funcs	*access;
	struct list_head			scan_el_dev_attr_list;
	struct attribute_group			scan_el_group;
	wait_queue_head_t			pollq;
	bool					stufftoread;
	const struct attribute_group *attrs;
	struct list_head			demux_list;
	void					*demux_bounce;
	struct list_head			buffer_list;
	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);

int iio_scan_mask_query(struct iio_dev *indio_dev,
			struct iio_buffer *buffer, int bit);

/**
 * iio_scan_mask_set() - set particular bit in the scan mask
 * @indio_dev		IIO device structure
 * @buffer:		the buffer whose scan mask we are interested in
 * @bit:		the bit to be set.
 **/
int iio_scan_mask_set(struct iio_dev *indio_dev,
		      struct iio_buffer *buffer, int bit);

/**
 * iio_push_to_buffers() - push to a registered buffer.
 * @indio_dev:		iio_dev structure for device.
 * @data:		Full scan.
 */
int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data);

/*
 * iio_push_to_buffers_with_timestamp() - push data and timestamp to buffers
 * @indio_dev:		iio_dev structure for device.
 * @data:		sample data
 * @timestamp:		timestamp for the sample data
 *
 * Pushes data to the IIO device's buffers. If timestamps are enabled for the
 * device the function will store the supplied timestamp as the last element in
 * the sample data buffer before pushing it to the device buffers. The sample
 * data buffer needs to be large enough to hold the additional timestamp
 * (usually the buffer should be indio->scan_bytes bytes large).
 *
 * Returns 0 on success, a negative error code otherwise.
 */
static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev,
	void *data, int64_t timestamp)
{
	if (indio_dev->scan_timestamp) {
		size_t ts_offset = indio_dev->scan_bytes / sizeof(int64_t) - 1;
		((int64_t *)data)[ts_offset] = timestamp;
	}

	return iio_push_to_buffers(indio_dev, data);
}

int iio_update_demux(struct iio_dev *indio_dev);

/**
 * iio_buffer_register() - register the buffer with IIO core
 * @indio_dev:		device with the buffer to be registered
 * @channels:		the channel descriptions used to construct buffer
 * @num_channels:	the number of channels
 **/
int iio_buffer_register(struct iio_dev *indio_dev,
			const struct iio_chan_spec *channels,
			int num_channels);

/**
 * iio_buffer_unregister() - unregister the buffer from IIO core
 * @indio_dev:		the device with the buffer to be unregistered
 **/
void iio_buffer_unregister(struct iio_dev *indio_dev);

/**
 * iio_buffer_read_length() - attr func to get number of datums in the buffer
 **/
ssize_t iio_buffer_read_length(struct device *dev,
			       struct device_attribute *attr,
			       char *buf);
/**
 * iio_buffer_write_length() - attr func to set number of datums in the buffer
 **/
ssize_t iio_buffer_write_length(struct device *dev,
			      struct device_attribute *attr,
			      const char *buf,
			      size_t len);
/**
 * iio_buffer_store_enable() - attr to turn the buffer on
 **/
ssize_t iio_buffer_store_enable(struct device *dev,
				struct device_attribute *attr,
				const char *buf,
				size_t len);
/**
 * iio_buffer_show_enable() - attr to see if the buffer is on
 **/
ssize_t iio_buffer_show_enable(struct device *dev,
			       struct device_attribute *attr,
			       char *buf);
#define IIO_BUFFER_LENGTH_ATTR DEVICE_ATTR(length, S_IRUGO | S_IWUSR,	\
					   iio_buffer_read_length,	\
					   iio_buffer_write_length)

#define IIO_BUFFER_ENABLE_ATTR DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,	\
					   iio_buffer_show_enable,	\
					   iio_buffer_store_enable)

bool iio_validate_scan_mask_onehot(struct iio_dev *indio_dev,
	const unsigned long *mask);

struct iio_buffer *iio_buffer_get(struct iio_buffer *buffer);
void iio_buffer_put(struct iio_buffer *buffer);

/**
 * iio_device_attach_buffer - Attach a buffer to a IIO device
 * @indio_dev: The device the buffer should be attached to
 * @buffer: The buffer to attach to the device
 *
 * This function attaches a buffer to a IIO device. The buffer stays attached to
 * the device until the device is freed. The function should only be called at
 * most once per device.
 */
static inline void iio_device_attach_buffer(struct iio_dev *indio_dev,
	struct iio_buffer *buffer)
{
	indio_dev->buffer = iio_buffer_get(buffer);
}

#else /* CONFIG_IIO_BUFFER */

static inline int iio_buffer_register(struct iio_dev *indio_dev,
					   const struct iio_chan_spec *channels,
					   int num_channels)
{
	return 0;
}

static inline void iio_buffer_unregister(struct iio_dev *indio_dev)
{}

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_H_ */