/* 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_ */