/*
   * Generic bounce buffer implementation
   *
   * Copyright (C) 2012 Marek Vasut <marex@denx.de>
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #ifndef __INCLUDE_BOUNCEBUF_H__
  #define __INCLUDE_BOUNCEBUF_H__
  
  #include <linux/types.h>
  
  /*
   * GEN_BB_READ -- Data are read from the buffer eg. by DMA hardware.
   * The source buffer is copied into the bounce buffer (if unaligned, otherwise
   * the source buffer is used directly) upon start() call, then the operation
   * requiring the aligned transfer happens, then the bounce buffer is lost upon
   * stop() call.
   */
  #define GEN_BB_READ	(1 << 0)
  /*
   * GEN_BB_WRITE -- Data are written into the buffer eg. by DMA hardware.
   * The source buffer starts in an undefined state upon start() call, then the
   * operation requiring the aligned transfer happens, then the bounce buffer is
   * copied into the destination buffer (if unaligned, otherwise destination
   * buffer is used directly) upon stop() call.
   */
  #define GEN_BB_WRITE	(1 << 1)
  /*
   * GEN_BB_RW -- Data are read and written into the buffer eg. by DMA hardware.
   * The source buffer is copied into the bounce buffer (if unaligned, otherwise
   * the source buffer is used directly) upon start() call, then the  operation
   * requiring the aligned transfer happens, then the bounce buffer is  copied
   * into the destination buffer (if unaligned, otherwise destination buffer is
   * used directly) upon stop() call.
   */
  #define GEN_BB_RW	(GEN_BB_READ | GEN_BB_WRITE)
  
  struct bounce_buffer {
  	/* Copy of data parameter passed to start() */
  	void *user_buffer;
  	/*
  	 * DMA-aligned buffer. This field is always set to the value that
  	 * should be used for DMA; either equal to .user_buffer, or to a
  	 * freshly allocated aligned buffer.
  	 */
  	void *bounce_buffer;
  	/* Copy of len parameter passed to start() */
  	size_t len;
  	/* DMA-aligned buffer length */
  	size_t len_aligned;
  	/* Copy of flags parameter passed to start() */
  	unsigned int flags;
  };
  
  /**
   * bounce_buffer_start() -- Start the bounce buffer session
   * state:	stores state passed between bounce_buffer_{start,stop}
   * data:	pointer to buffer to be aligned
   * len:		length of the buffer
   * flags:	flags describing the transaction, see above.
   */
  int bounce_buffer_start(struct bounce_buffer *state, void *data,
  			size_t len, unsigned int flags);
  /**
   * bounce_buffer_stop() -- Finish the bounce buffer session
   * state:	stores state passed between bounce_buffer_{start,stop}
   */
  int bounce_buffer_stop(struct bounce_buffer *state);
  
  #endif