/*

   * A generic kernel FIFO implementation

   *

   * Copyright (C) 2013 Stefani Seibold <stefani@seibold.net>

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
   *
   */

  #ifndef _LINUX_KFIFO_H
  #define _LINUX_KFIFO_H

  /*

   * How to porting drivers to the new generic FIFO API:

   *
   * - Modify the declaration of the "struct kfifo *" object into a
   *   in-place "struct kfifo" object
   * - Init the in-place object with kfifo_alloc() or kfifo_init()
   *   Note: The address of the in-place "struct kfifo" object must be
   *   passed as the first argument to this functions
   * - Replace the use of __kfifo_put into kfifo_in and __kfifo_get
   *   into kfifo_out

   * - Replace the use of kfifo_put into kfifo_in_spinlocked and kfifo_get
   *   into kfifo_out_spinlocked

   *   Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc

   *   must be passed now to the kfifo_in_spinlocked and kfifo_out_spinlocked
   *   as the last parameter
   * - The formerly __kfifo_* functions are renamed into kfifo_*

   */

  /*
   * Note about locking : There is no locking required until only * one reader
   * and one writer is using the fifo and no kfifo_reset() will be * called
   *  kfifo_reset_out() can be safely used, until it will be only called
   * in the reader thread.
   *  For multiple writer and one reader there is only a need to lock the writer.
   * And vice versa for only one writer and multiple reader there is only a need
   * to lock the reader.
   */

  #include <linux/kernel.h>
  #include <linux/spinlock.h>

  #include <linux/stddef.h>
  #include <linux/scatterlist.h>
  
  struct __kfifo {
  	unsigned int	in;
  	unsigned int	out;
  	unsigned int	mask;
  	unsigned int	esize;
  	void		*data;

  };

  #define __STRUCT_KFIFO_COMMON(datatype, recsize, ptrtype) \
  	union { \
  		struct __kfifo	kfifo; \
  		datatype	*type; \

  		const datatype	*const_type; \

  		char		(*rectype)[recsize]; \
  		ptrtype		*ptr; \

  		ptrtype const	*ptr_const; \

  	}

  #define __STRUCT_KFIFO(type, size, recsize, ptrtype) \
  { \
  	__STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
  	type		buf[((size < 2) || (size & (size - 1))) ? -1 : size]; \

  }

  #define STRUCT_KFIFO(type, size) \
  	struct __STRUCT_KFIFO(type, size, 0, type)
  
  #define __STRUCT_KFIFO_PTR(type, recsize, ptrtype) \
  { \
  	__STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
  	type		buf[0]; \
  }
  
  #define STRUCT_KFIFO_PTR(type) \
  	struct __STRUCT_KFIFO_PTR(type, 0, type)
  
  /*
   * define compatibility "struct kfifo" for dynamic allocated fifos

   */

  struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0, void);

  #define STRUCT_KFIFO_REC_1(size) \
  	struct __STRUCT_KFIFO(unsigned char, size, 1, void)
  
  #define STRUCT_KFIFO_REC_2(size) \
  	struct __STRUCT_KFIFO(unsigned char, size, 2, void)
  
  /*
   * define kfifo_rec types

   */

  struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, 1, void);
  struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void);

  /*
   * helper macro to distinguish between real in place fifo where the fifo
   * array is a part of the structure and the fifo type where the array is
   * outside of the fifo structure.
   */
  #define	__is_kfifo_ptr(fifo)	(sizeof(*fifo) == sizeof(struct __kfifo))

  /**

   * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object
   * @fifo: name of the declared fifo
   * @type: type of the fifo elements

   */

  #define DECLARE_KFIFO_PTR(fifo, type)	STRUCT_KFIFO_PTR(type) fifo

  
  /**

   * DECLARE_KFIFO - macro to declare a fifo object
   * @fifo: name of the declared fifo
   * @type: type of the fifo elements
   * @size: the number of elements in the fifo, this must be a power of 2

   */

  #define DECLARE_KFIFO(fifo, type, size)	STRUCT_KFIFO(type, size) fifo

  
  /**

   * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO
   * @fifo: name of the declared fifo datatype
   */
  #define INIT_KFIFO(fifo) \
  (void)({ \
  	typeof(&(fifo)) __tmp = &(fifo); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	__kfifo->in = 0; \
  	__kfifo->out = 0; \
  	__kfifo->mask = __is_kfifo_ptr(__tmp) ? 0 : ARRAY_SIZE(__tmp->buf) - 1;\
  	__kfifo->esize = sizeof(*__tmp->buf); \
  	__kfifo->data = __is_kfifo_ptr(__tmp) ?  NULL : __tmp->buf; \
  })

  
  /**

   * DEFINE_KFIFO - macro to define and initialize a fifo
   * @fifo: name of the declared fifo datatype
   * @type: type of the fifo elements
   * @size: the number of elements in the fifo, this must be a power of 2
   *
   * Note: the macro can be used for global and local fifo data type variables.
   */
  #define DEFINE_KFIFO(fifo, type, size) \
  	DECLARE_KFIFO(fifo, type, size) = \
  	(typeof(fifo)) { \
  		{ \
  			{ \
  			.in	= 0, \
  			.out	= 0, \
  			.mask	= __is_kfifo_ptr(&(fifo)) ? \
  				  0 : \
  				  ARRAY_SIZE((fifo).buf) - 1, \
  			.esize	= sizeof(*(fifo).buf), \
  			.data	= __is_kfifo_ptr(&(fifo)) ? \
  				NULL : \
  				(fifo).buf, \
  			} \
  		} \
  	}

  static inline unsigned int __must_check
  __kfifo_uint_must_check_helper(unsigned int val)
  {
  	return val;
  }
  
  static inline int __must_check
  __kfifo_int_must_check_helper(int val)
  {
  	return val;
  }

  
  /**

   * kfifo_initialized - Check if the fifo is initialized
   * @fifo: address of the fifo to check
   *
   * Return %true if fifo is initialized, otherwise %false.
   * Assumes the fifo was 0 before.

   */

  #define kfifo_initialized(fifo) ((fifo)->kfifo.mask)

  
  /**

   * kfifo_esize - returns the size of the element managed by the fifo
   * @fifo: address of the fifo to be used

   */

  #define kfifo_esize(fifo)	((fifo)->kfifo.esize)

  
  /**

   * kfifo_recsize - returns the size of the record length field
   * @fifo: address of the fifo to be used

   */

  #define kfifo_recsize(fifo)	(sizeof(*(fifo)->rectype))

  
  /**

   * kfifo_size - returns the size of the fifo in elements
   * @fifo: address of the fifo to be used

   */

  #define kfifo_size(fifo)	((fifo)->kfifo.mask + 1)

  
  /**

   * kfifo_reset - removes the entire fifo content
   * @fifo: address of the fifo to be used

   *

   * Note: usage of kfifo_reset() is dangerous. It should be only called when the
   * fifo is exclusived locked or when it is secured that no other thread is
   * accessing the fifo.

   */

  #define kfifo_reset(fifo) \
  (void)({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	__tmp->kfifo.in = __tmp->kfifo.out = 0; \
  })

  
  /**

   * kfifo_reset_out - skip fifo content
   * @fifo: address of the fifo to be used

   *

   * Note: The usage of kfifo_reset_out() is safe until it will be only called
   * from the reader thread and there is only one concurrent reader. Otherwise
   * it is dangerous and must be handled in the same way as kfifo_reset().

   */

  #define kfifo_reset_out(fifo)	\
  (void)({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	__tmp->kfifo.out = __tmp->kfifo.in; \
  })

  /**
   * kfifo_len - returns the number of used elements in the fifo
   * @fifo: address of the fifo to be used

   */

  #define kfifo_len(fifo) \
  ({ \

  	typeof((fifo) + 1) __tmpl = (fifo); \

  	__tmpl->kfifo.in - __tmpl->kfifo.out; \
  })

  /**
   * kfifo_is_empty - returns true if the fifo is empty
   * @fifo: address of the fifo to be used

   */

  #define	kfifo_is_empty(fifo) \
  ({ \

  	typeof((fifo) + 1) __tmpq = (fifo); \

  	__tmpq->kfifo.in == __tmpq->kfifo.out; \
  })

  /**
   * kfifo_is_full - returns true if the fifo is full
   * @fifo: address of the fifo to be used

   */

  #define	kfifo_is_full(fifo) \
  ({ \

  	typeof((fifo) + 1) __tmpq = (fifo); \

  	kfifo_len(__tmpq) > __tmpq->kfifo.mask; \
  })

  /**
   * kfifo_avail - returns the number of unused elements in the fifo
   * @fifo: address of the fifo to be used
   */
  #define	kfifo_avail(fifo) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmpq = (fifo); \

  	const size_t __recsize = sizeof(*__tmpq->rectype); \
  	unsigned int __avail = kfifo_size(__tmpq) - kfifo_len(__tmpq); \
  	(__recsize) ? ((__avail <= __recsize) ? 0 : \
  	__kfifo_max_r(__avail - __recsize, __recsize)) : \
  	__avail; \
  }) \
  )

  /**
   * kfifo_skip - skip output data
   * @fifo: address of the fifo to be used
   */
  #define	kfifo_skip(fifo) \
  (void)({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	if (__recsize) \
  		__kfifo_skip_r(__kfifo, __recsize); \
  	else \
  		__kfifo->out++; \
  })

  /**
   * kfifo_peek_len - gets the size of the next fifo record
   * @fifo: address of the fifo to be used
   *
   * This function returns the size of the next fifo record in number of bytes.
   */
  #define kfifo_peek_len(fifo) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	(!__recsize) ? kfifo_len(__tmp) * sizeof(*__tmp->type) : \
  	__kfifo_len_r(__kfifo, __recsize); \
  }) \
  )

  /**
   * kfifo_alloc - dynamically allocates a new fifo buffer
   * @fifo: pointer to the fifo
   * @size: the number of elements in the fifo, this must be a power of 2
   * @gfp_mask: get_free_pages mask, passed to kmalloc()
   *
   * This macro dynamically allocates a new fifo buffer.
   *
   * The numer of elements will be rounded-up to a power of 2.
   * The fifo will be release with kfifo_free().
   * Return 0 if no error, otherwise an error code.
   */
  #define kfifo_alloc(fifo, size, gfp_mask) \

  __kfifo_int_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	__is_kfifo_ptr(__tmp) ? \
  	__kfifo_alloc(__kfifo, size, sizeof(*__tmp->type), gfp_mask) : \
  	-EINVAL; \
  }) \
  )

  /**
   * kfifo_free - frees the fifo
   * @fifo: the fifo to be freed

   */

  #define kfifo_free(fifo) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	if (__is_kfifo_ptr(__tmp)) \
  		__kfifo_free(__kfifo); \
  })

  /**
   * kfifo_init - initialize a fifo using a preallocated buffer
   * @fifo: the fifo to assign the buffer
   * @buffer: the preallocated buffer to be used
   * @size: the size of the internal buffer, this have to be a power of 2
   *
   * This macro initialize a fifo using a preallocated buffer.
   *
   * The numer of elements will be rounded-up to a power of 2.
   * Return 0 if no error, otherwise an error code.
   */
  #define kfifo_init(fifo, buffer, size) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	__is_kfifo_ptr(__tmp) ? \
  	__kfifo_init(__kfifo, buffer, size, sizeof(*__tmp->type)) : \
  	-EINVAL; \
  })

  /**
   * kfifo_put - put data into the fifo
   * @fifo: address of the fifo to be used
   * @val: the data to be added
   *
   * This macro copies the given value into the fifo.
   * It returns 0 if the fifo was full. Otherwise it returns the number
   * processed elements.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_put(fifo, val) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(*__tmp->const_type) __val = (val); \

  	unsigned int __ret; \

  	size_t __recsize = sizeof(*__tmp->rectype); \

  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	if (__recsize) \

  		__ret = __kfifo_in_r(__kfifo, &__val, sizeof(__val), \

  			__recsize); \
  	else { \
  		__ret = !kfifo_is_full(__tmp); \
  		if (__ret) { \
  			(__is_kfifo_ptr(__tmp) ? \
  			((typeof(__tmp->type))__kfifo->data) : \
  			(__tmp->buf) \
  			)[__kfifo->in & __tmp->kfifo.mask] = \

  				*(typeof(__tmp->type))&__val; \

  			smp_wmb(); \
  			__kfifo->in++; \
  		} \
  	} \
  	__ret; \
  })

  /**
   * kfifo_get - get data from the fifo
   * @fifo: address of the fifo to be used

   * @val: address where to store the data

   *
   * This macro reads the data from the fifo.
   * It returns 0 if the fifo was empty. Otherwise it returns the number
   * processed elements.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_get(fifo, val) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(__tmp->ptr) __val = (val); \

  	unsigned int __ret; \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	if (__recsize) \
  		__ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), \
  			__recsize); \
  	else { \
  		__ret = !kfifo_is_empty(__tmp); \
  		if (__ret) { \
  			*(typeof(__tmp->type))__val = \
  				(__is_kfifo_ptr(__tmp) ? \
  				((typeof(__tmp->type))__kfifo->data) : \
  				(__tmp->buf) \
  				)[__kfifo->out & __tmp->kfifo.mask]; \
  			smp_wmb(); \
  			__kfifo->out++; \
  		} \
  	} \
  	__ret; \
  }) \
  )

  /**
   * kfifo_peek - get data from the fifo without removing
   * @fifo: address of the fifo to be used

   * @val: address where to store the data

   *
   * This reads the data from the fifo without removing it from the fifo.
   * It returns 0 if the fifo was empty. Otherwise it returns the number
   * processed elements.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_peek(fifo, val) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(__tmp->ptr) __val = (val); \

  	unsigned int __ret; \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	if (__recsize) \
  		__ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), \
  			__recsize); \
  	else { \
  		__ret = !kfifo_is_empty(__tmp); \
  		if (__ret) { \
  			*(typeof(__tmp->type))__val = \
  				(__is_kfifo_ptr(__tmp) ? \
  				((typeof(__tmp->type))__kfifo->data) : \
  				(__tmp->buf) \
  				)[__kfifo->out & __tmp->kfifo.mask]; \
  			smp_wmb(); \
  		} \
  	} \
  	__ret; \
  }) \
  )

  /**
   * kfifo_in - put data into the fifo
   * @fifo: address of the fifo to be used
   * @buf: the data to be added
   * @n: number of elements to be added
   *
   * This macro copies the given buffer into the fifo and returns the
   * number of copied elements.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_in(fifo, buf, n) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(__tmp->ptr_const) __buf = (buf); \

  	unsigned long __n = (n); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	(__recsize) ?\
  	__kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
  	__kfifo_in(__kfifo, __buf, __n); \
  })

  /**
   * kfifo_in_spinlocked - put data into the fifo using a spinlock for locking
   * @fifo: address of the fifo to be used
   * @buf: the data to be added
   * @n: number of elements to be added
   * @lock: pointer to the spinlock to use for locking
   *
   * This macro copies the given values buffer into the fifo and returns the
   * number of copied elements.
   */
  #define	kfifo_in_spinlocked(fifo, buf, n, lock) \
  ({ \
  	unsigned long __flags; \
  	unsigned int __ret; \
  	spin_lock_irqsave(lock, __flags); \
  	__ret = kfifo_in(fifo, buf, n); \
  	spin_unlock_irqrestore(lock, __flags); \
  	__ret; \
  })
  
  /* alias for kfifo_in_spinlocked, will be removed in a future release */
  #define kfifo_in_locked(fifo, buf, n, lock) \
  		kfifo_in_spinlocked(fifo, buf, n, lock)

  /**
   * kfifo_out - get data from the fifo
   * @fifo: address of the fifo to be used
   * @buf: pointer to the storage buffer
   * @n: max. number of elements to get
   *
   * This macro get some data from the fifo and return the numbers of elements
   * copied.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_out(fifo, buf, n) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(__tmp->ptr) __buf = (buf); \

  	unsigned long __n = (n); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	(__recsize) ?\
  	__kfifo_out_r(__kfifo, __buf, __n, __recsize) : \
  	__kfifo_out(__kfifo, __buf, __n); \
  }) \
  )
  
  /**
   * kfifo_out_spinlocked - get data from the fifo using a spinlock for locking
   * @fifo: address of the fifo to be used
   * @buf: pointer to the storage buffer
   * @n: max. number of elements to get
   * @lock: pointer to the spinlock to use for locking
   *
   * This macro get the data from the fifo and return the numbers of elements
   * copied.
   */
  #define	kfifo_out_spinlocked(fifo, buf, n, lock) \

  __kfifo_uint_must_check_helper( \

  ({ \
  	unsigned long __flags; \
  	unsigned int __ret; \
  	spin_lock_irqsave(lock, __flags); \
  	__ret = kfifo_out(fifo, buf, n); \
  	spin_unlock_irqrestore(lock, __flags); \
  	__ret; \
  }) \
  )
  
  /* alias for kfifo_out_spinlocked, will be removed in a future release */
  #define kfifo_out_locked(fifo, buf, n, lock) \
  		kfifo_out_spinlocked(fifo, buf, n, lock)

  
  /**

   * kfifo_from_user - puts some data from user space into the fifo
   * @fifo: address of the fifo to be used
   * @from: pointer to the data to be added
   * @len: the length of the data to be added
   * @copied: pointer to output variable to store the number of copied bytes

   *

   * This macro copies at most @len bytes from the @from into the
   * fifo, depending of the available space and returns -EFAULT/0.

   *
   * Note that with only one concurrent reader and one concurrent

   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_from_user(fifo, from, len, copied) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	const void __user *__from = (from); \
  	unsigned int __len = (len); \
  	unsigned int *__copied = (copied); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	(__recsize) ? \
  	__kfifo_from_user_r(__kfifo, __from, __len,  __copied, __recsize) : \
  	__kfifo_from_user(__kfifo, __from, __len, __copied); \
  }) \
  )

  /**
   * kfifo_to_user - copies data from the fifo into user space
   * @fifo: address of the fifo to be used
   * @to: where the data must be copied
   * @len: the size of the destination buffer
   * @copied: pointer to output variable to store the number of copied bytes
   *
   * This macro copies at most @len bytes from the fifo into the
   * @to buffer and returns -EFAULT/0.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macro.
   */
  #define	kfifo_to_user(fifo, to, len, copied) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	void __user *__to = (to); \
  	unsigned int __len = (len); \
  	unsigned int *__copied = (copied); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	(__recsize) ? \
  	__kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : \
  	__kfifo_to_user(__kfifo, __to, __len, __copied); \
  }) \
  )
  
  /**
   * kfifo_dma_in_prepare - setup a scatterlist for DMA input
   * @fifo: address of the fifo to be used
   * @sgl: pointer to the scatterlist array
   * @nents: number of entries in the scatterlist array
   * @len: number of elements to transfer
   *
   * This macro fills a scatterlist for DMA input.
   * It returns the number entries in the scatterlist array.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macros.
   */
  #define	kfifo_dma_in_prepare(fifo, sgl, nents, len) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	struct scatterlist *__sgl = (sgl); \
  	int __nents = (nents); \
  	unsigned int __len = (len); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	(__recsize) ? \
  	__kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
  	__kfifo_dma_in_prepare(__kfifo, __sgl, __nents, __len); \
  })

  /**
   * kfifo_dma_in_finish - finish a DMA IN operation
   * @fifo: address of the fifo to be used
   * @len: number of bytes to received
   *
   * This macro finish a DMA IN operation. The in counter will be updated by
   * the len parameter. No error checking will be done.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macros.
   */
  #define kfifo_dma_in_finish(fifo, len) \
  (void)({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	unsigned int __len = (len); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	if (__recsize) \
  		__kfifo_dma_in_finish_r(__kfifo, __len, __recsize); \
  	else \
  		__kfifo->in += __len / sizeof(*__tmp->type); \
  })

  /**
   * kfifo_dma_out_prepare - setup a scatterlist for DMA output
   * @fifo: address of the fifo to be used
   * @sgl: pointer to the scatterlist array
   * @nents: number of entries in the scatterlist array
   * @len: number of elements to transfer
   *
   * This macro fills a scatterlist for DMA output which at most @len bytes
   * to transfer.
   * It returns the number entries in the scatterlist array.
   * A zero means there is no space available and the scatterlist is not filled.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macros.
   */
  #define	kfifo_dma_out_prepare(fifo, sgl, nents, len) \
  ({ \

  	typeof((fifo) + 1) __tmp = (fifo);  \

  	struct scatterlist *__sgl = (sgl); \
  	int __nents = (nents); \
  	unsigned int __len = (len); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	(__recsize) ? \
  	__kfifo_dma_out_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : \
  	__kfifo_dma_out_prepare(__kfifo, __sgl, __nents, __len); \
  })

  /**
   * kfifo_dma_out_finish - finish a DMA OUT operation
   * @fifo: address of the fifo to be used

   * @len: number of bytes transferred

   *
   * This macro finish a DMA OUT operation. The out counter will be updated by
   * the len parameter. No error checking will be done.
   *
   * Note that with only one concurrent reader and one concurrent
   * writer, you don't need extra locking to use these macros.
   */
  #define kfifo_dma_out_finish(fifo, len) \
  (void)({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	unsigned int __len = (len); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \
  	if (__recsize) \
  		__kfifo_dma_out_finish_r(__kfifo, __recsize); \
  	else \
  		__kfifo->out += __len / sizeof(*__tmp->type); \
  })

  
  /**

   * kfifo_out_peek - gets some data from the fifo
   * @fifo: address of the fifo to be used
   * @buf: pointer to the storage buffer
   * @n: max. number of elements to get

   *

   * This macro get the data from the fifo and return the numbers of elements
   * copied. The data is not removed from the fifo.

   *
   * Note that with only one concurrent reader and one concurrent

   * writer, you don't need extra locking to use these macro.

   */

  #define	kfifo_out_peek(fifo, buf, n) \

  __kfifo_uint_must_check_helper( \

  ({ \

  	typeof((fifo) + 1) __tmp = (fifo); \

  	typeof(__tmp->ptr) __buf = (buf); \

  	unsigned long __n = (n); \
  	const size_t __recsize = sizeof(*__tmp->rectype); \
  	struct __kfifo *__kfifo = &__tmp->kfifo; \

  	(__recsize) ? \
  	__kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : \
  	__kfifo_out_peek(__kfifo, __buf, __n); \
  }) \
  )

  extern int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,
  	size_t esize, gfp_t gfp_mask);

  extern void __kfifo_free(struct __kfifo *fifo);

  extern int __kfifo_init(struct __kfifo *fifo, void *buffer,
  	unsigned int size, size_t esize);

  extern unsigned int __kfifo_in(struct __kfifo *fifo,
  	const void *buf, unsigned int len);

  extern unsigned int __kfifo_out(struct __kfifo *fifo,
  	void *buf, unsigned int len);

  extern int __kfifo_from_user(struct __kfifo *fifo,
  	const void __user *from, unsigned long len, unsigned int *copied);

  extern int __kfifo_to_user(struct __kfifo *fifo,
  	void __user *to, unsigned long len, unsigned int *copied);

  extern unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,
  	struct scatterlist *sgl, int nents, unsigned int len);

  extern unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,
  	struct scatterlist *sgl, int nents, unsigned int len);

  extern unsigned int __kfifo_out_peek(struct __kfifo *fifo,
  	void *buf, unsigned int len);

  extern unsigned int __kfifo_in_r(struct __kfifo *fifo,
  	const void *buf, unsigned int len, size_t recsize);

  extern unsigned int __kfifo_out_r(struct __kfifo *fifo,
  	void *buf, unsigned int len, size_t recsize);

  extern int __kfifo_from_user_r(struct __kfifo *fifo,
  	const void __user *from, unsigned long len, unsigned int *copied,
  	size_t recsize);

  extern int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,
  	unsigned long len, unsigned int *copied, size_t recsize);

  extern unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,
  	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize);

  extern void __kfifo_dma_in_finish_r(struct __kfifo *fifo,
  	unsigned int len, size_t recsize);

  extern unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,
  	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize);

  extern void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize);

  extern unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize);

  extern void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize);

  extern unsigned int __kfifo_out_peek_r(struct __kfifo *fifo,
  	void *buf, unsigned int len, size_t recsize);

  extern unsigned int __kfifo_max_r(unsigned int len, size_t recsize);

  #endif