include/linux/kfifo.h - kernel/skids - Git at Google

 /*
  * A generic kernel FIFO implementation.
  *
  * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
  * Copyright (C) 2004 Stelian Pop <stelian@popies.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.
  *
  */

 /*
  * Howto 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_locked and kfifo_get
  *   into kfifo_out_locked
  *   Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc
  *   must be passed now to the kfifo_in_locked and kfifo_out_locked
  *   as the last parameter.
  * - All formerly name __kfifo_* functions has been renamed into kfifo_*
  */

 #ifndef _LINUX_KFIFO_H
 #define _LINUX_KFIFO_H

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

 struct kfifo {
 	unsigned char *buffer;	/* the buffer holding the data */
 	unsigned int size;	/* the size of the allocated buffer */
 	unsigned int in;	/* data is added at offset (in % size) */
 	unsigned int out;	/* data is extracted from off. (out % size) */
 };

 /*
  * Macros for declaration and initialization of the kfifo datatype
  */

 /* helper macro */
 #define __kfifo_initializer(s, b) \
 	(struct kfifo) { \
 		.size	= s, \
 		.in	= 0, \
 		.out	= 0, \
 		.buffer = b \
 	}

 /**
  * DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
  * @name: name of the declared kfifo datatype
  * @size: size of the fifo buffer. Must be a power of two.
  *
  * Note1: the macro can be used inside struct or union declaration
  * Note2: the macro creates two objects:
  *  A kfifo object with the given name and a buffer for the kfifo
  *  object named name##kfifo_buffer
  */
 #define DECLARE_KFIFO(name, size) \
 union { \
 	struct kfifo name; \
 	unsigned char name##kfifo_buffer[size + sizeof(struct kfifo)]; \
 }

 /**
  * INIT_KFIFO - Initialize a kfifo declared by DECLARE_KFIFO
  * @name: name of the declared kfifo datatype
  */
 #define INIT_KFIFO(name) \
 	name = __kfifo_initializer(sizeof(name##kfifo_buffer) - \
 				sizeof(struct kfifo), \
 				name##kfifo_buffer + sizeof(struct kfifo))

 /**
  * DEFINE_KFIFO - macro to define and initialize a kfifo
  * @name: name of the declared kfifo datatype
  * @size: size of the fifo buffer. Must be a power of two.
  *
  * Note1: the macro can be used for global and local kfifo data type variables
  * Note2: the macro creates two objects:
  *  A kfifo object with the given name and a buffer for the kfifo
  *  object named name##kfifo_buffer
  */
 #define DEFINE_KFIFO(name, size) \
 	unsigned char name##kfifo_buffer[size]; \
 	struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)

 extern void kfifo_init(struct kfifo *fifo, void *buffer,
 			unsigned int size);
 extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
 			gfp_t gfp_mask);
 extern void kfifo_free(struct kfifo *fifo);
 extern unsigned int kfifo_in(struct kfifo *fifo,
 				const void *from, unsigned int len);
 extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
 				void *to, unsigned int len);
 extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
 				void *to, unsigned int len, unsigned offset);

 /**
  * kfifo_initialized - Check if kfifo is initialized.
  * @fifo: fifo to check
  * Return %true if FIFO is initialized, otherwise %false.
  * Assumes the fifo was 0 before.
  */
 static inline bool kfifo_initialized(struct kfifo *fifo)
 {
 	return fifo->buffer != NULL;
 }

 /**
  * kfifo_reset - removes the entire FIFO contents
  * @fifo: the fifo to be emptied.
  */
 static inline void kfifo_reset(struct kfifo *fifo)
 {
 	fifo->in = fifo->out = 0;
 }

 /**
  * kfifo_reset_out - skip FIFO contents
  * @fifo: the fifo to be emptied.
  */
 static inline void kfifo_reset_out(struct kfifo *fifo)
 {
 	smp_mb();
 	fifo->out = fifo->in;
 }

 /**
  * kfifo_size - returns the size of the fifo in bytes
  * @fifo: the fifo to be used.
  */
 static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
 {
 	return fifo->size;
 }

 /**
  * kfifo_len - returns the number of used bytes in the FIFO
  * @fifo: the fifo to be used.
  */
 static inline unsigned int kfifo_len(struct kfifo *fifo)
 {
 	register unsigned int	out;

 	out = fifo->out;
 	smp_rmb();
 	return fifo->in - out;
 }

 /**
  * kfifo_is_empty - returns true if the fifo is empty
  * @fifo: the fifo to be used.
  */
 static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
 {
 	return fifo->in == fifo->out;
 }

 /**
  * kfifo_is_full - returns true if the fifo is full
  * @fifo: the fifo to be used.
  */
 static inline __must_check int kfifo_is_full(struct kfifo *fifo)
 {
 	return kfifo_len(fifo) == kfifo_size(fifo);
 }

 /**
  * kfifo_avail - returns the number of bytes available in the FIFO
  * @fifo: the fifo to be used.
  */
 static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
 {
 	return kfifo_size(fifo) - kfifo_len(fifo);
 }

 /**
  * kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
  * @fifo: the fifo to be used.
  * @from: the data to be added.
  * @n: the length of the data to be added.
  * @lock: pointer to the spinlock to use for locking.
  *
  * This function copies at most @n bytes from the @from buffer into
  * the FIFO depending on the free space, and returns the number of
  * bytes copied.
  */
 static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
 		const void *from, unsigned int n, spinlock_t *lock)
 {
 	unsigned long flags;
 	unsigned int ret;

 	spin_lock_irqsave(lock, flags);

 	ret = kfifo_in(fifo, from, n);

 	spin_unlock_irqrestore(lock, flags);

 	return ret;
 }

 /**
  * kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @n: the size of the destination buffer.
  * @lock: pointer to the spinlock to use for locking.
  *
  * This function copies at most @n bytes from the FIFO into the
  * @to buffer and returns the number of copied bytes.
  */
 static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
 	void *to, unsigned int n, spinlock_t *lock)
 {
 	unsigned long flags;
 	unsigned int ret;

 	spin_lock_irqsave(lock, flags);

 	ret = kfifo_out(fifo, to, n);

 	spin_unlock_irqrestore(lock, flags);

 	return ret;
 }

 extern void kfifo_skip(struct kfifo *fifo, unsigned int len);

 extern __must_check int kfifo_from_user(struct kfifo *fifo,
 	const void __user *from, unsigned int n, unsigned *lenout);

 extern __must_check int kfifo_to_user(struct kfifo *fifo,
 	void __user *to, unsigned int n, unsigned *lenout);

 /*
  * __kfifo_add_out internal helper function for updating the out offset
  */
 static inline void __kfifo_add_out(struct kfifo *fifo,
 				unsigned int off)
 {
 	smp_mb();
 	fifo->out += off;
 }

 /*
  * __kfifo_add_in internal helper function for updating the in offset
  */
 static inline void __kfifo_add_in(struct kfifo *fifo,
 				unsigned int off)
 {
 	smp_wmb();
 	fifo->in += off;
 }

 /*
  * __kfifo_off internal helper function for calculating the index of a
  * given offeset
  */
 static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
 {
 	return off & (fifo->size - 1);
 }

 /*
  * __kfifo_peek_n internal helper function for determinate the length of
  * the next record in the fifo
  */
 static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
 				unsigned int recsize)
 {
 #define __KFIFO_GET(fifo, off, shift) \
 	((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))

 	unsigned int l;

 	l = __KFIFO_GET(fifo, 0, 0);

 	if (--recsize)
 		l |= __KFIFO_GET(fifo, 1, 8);

 	return l;
 #undef	__KFIFO_GET
 }

 /*
  * __kfifo_poke_n internal helper function for storing the length of
  * the next record into the fifo
  */
 static inline void __kfifo_poke_n(struct kfifo *fifo,
 			unsigned int recsize, unsigned int n)
 {
 #define __KFIFO_PUT(fifo, off, val, shift) \
 		( \
 		(fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
 		(unsigned char)((val) >> (shift)) \
 		)

 	__KFIFO_PUT(fifo, 0, n, 0);

 	if (--recsize)
 		__KFIFO_PUT(fifo, 1, n, 8);
 #undef	__KFIFO_PUT
 }

 /*
  * __kfifo_in_... internal functions for put date into the fifo
  * do not call it directly, use kfifo_in_rec() instead
  */
 extern unsigned int __kfifo_in_n(struct kfifo *fifo,
 	const void *from, unsigned int n, unsigned int recsize);

 extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
 	const void *from, unsigned int n, unsigned int recsize);

 static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
 	const void *from, unsigned int n, unsigned int recsize)
 {
 	unsigned int ret;

 	ret = __kfifo_in_n(fifo, from, n, recsize);

 	if (likely(ret == 0)) {
 		if (recsize)
 			__kfifo_poke_n(fifo, recsize, n);
 		__kfifo_add_in(fifo, n + recsize);
 	}
 	return ret;
 }

 /**
  * kfifo_in_rec - puts some record data into the FIFO
  * @fifo: the fifo to be used.
  * @from: the data to be added.
  * @n: the length of the data to be added.
  * @recsize: size of record field
  *
  * This function copies @n bytes from the @from into the FIFO and returns
  * the number of bytes which cannot be copied.
  * A returned value greater than the @n value means that the record doesn't
  * fit into the buffer.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
 	void *from, unsigned int n, unsigned int recsize)
 {
 	if (!__builtin_constant_p(recsize))
 		return __kfifo_in_generic(fifo, from, n, recsize);
 	return __kfifo_in_rec(fifo, from, n, recsize);
 }

 /*
  * __kfifo_out_... internal functions for get date from the fifo
  * do not call it directly, use kfifo_out_rec() instead
  */
 extern unsigned int __kfifo_out_n(struct kfifo *fifo,
 	void *to, unsigned int reclen, unsigned int recsize);

 extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
 	void *to, unsigned int n,
 	unsigned int recsize, unsigned int *total);

 static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
 	void *to, unsigned int n, unsigned int recsize,
 	unsigned int *total)
 {
 	unsigned int l;

 	if (!recsize) {
 		l = n;
 		if (total)
 			*total = l;
 	} else {
 		l = __kfifo_peek_n(fifo, recsize);
 		if (total)
 			*total = l;
 		if (n < l)
 			return l;
 	}

 	return __kfifo_out_n(fifo, to, l, recsize);
 }

 /**
  * kfifo_out_rec - gets some record data from the FIFO
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @n: the size of the destination buffer.
  * @recsize: size of record field
  * @total: pointer where the total number of to copied bytes should stored
  *
  * This function copies at most @n bytes from the FIFO to @to and returns the
  * number of bytes which cannot be copied.
  * A returned value greater than the @n value means that the record doesn't
  * fit into the @to buffer.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
 	void *to, unsigned int n, unsigned int recsize,
 	unsigned int *total)

 {
 	if (!__builtin_constant_p(recsize))
 		return __kfifo_out_generic(fifo, to, n, recsize, total);
 	return __kfifo_out_rec(fifo, to, n, recsize, total);
 }

 /*
  * __kfifo_from_user_... internal functions for transfer from user space into
  * the fifo. do not call it directly, use kfifo_from_user_rec() instead
  */
 extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
 	const void __user *from, unsigned int n, unsigned int recsize);

 extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
 	const void __user *from, unsigned int n, unsigned int recsize);

 static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
 	const void __user *from, unsigned int n, unsigned int recsize)
 {
 	unsigned int ret;

 	ret = __kfifo_from_user_n(fifo, from, n, recsize);

 	if (likely(ret == 0)) {
 		if (recsize)
 			__kfifo_poke_n(fifo, recsize, n);
 		__kfifo_add_in(fifo, n + recsize);
 	}
 	return ret;
 }

 /**
  * kfifo_from_user_rec - puts some data from user space into the FIFO
  * @fifo: the fifo to be used.
  * @from: pointer to the data to be added.
  * @n: the length of the data to be added.
  * @recsize: size of record field
  *
  * This function copies @n bytes from the @from into the
  * FIFO and returns the number of bytes which cannot be copied.
  *
  * If the returned value is equal or less the @n value, the copy_from_user()
  * functions has failed. Otherwise the record doesn't fit into the buffer.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
 	const void __user *from, unsigned int n, unsigned int recsize)
 {
 	if (!__builtin_constant_p(recsize))
 		return __kfifo_from_user_generic(fifo, from, n, recsize);
 	return __kfifo_from_user_rec(fifo, from, n, recsize);
 }

 /*
  * __kfifo_to_user_... internal functions for transfer fifo data into user space
  * do not call it directly, use kfifo_to_user_rec() instead
  */
 extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
 	void __user *to, unsigned int n, unsigned int reclen,
 	unsigned int recsize);

 extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
 	void __user *to, unsigned int n, unsigned int recsize,
 	unsigned int *total);

 static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
 	void __user *to, unsigned int n,
 	unsigned int recsize, unsigned int *total)
 {
 	unsigned int l;

 	if (!recsize) {
 		l = n;
 		if (total)
 			*total = l;
 	} else {
 		l = __kfifo_peek_n(fifo, recsize);
 		if (total)
 			*total = l;
 		if (n < l)
 			return l;
 	}

 	return __kfifo_to_user_n(fifo, to, n, l, recsize);
 }

 /**
  * kfifo_to_user_rec - gets data from the FIFO and write it to user space
  * @fifo: the fifo to be used.
  * @to: where the data must be copied.
  * @n: the size of the destination buffer.
  * @recsize: size of record field
  * @total: pointer where the total number of to copied bytes should stored
  *
  * This function copies at most @n bytes from the FIFO to the @to.
  * In case of an error, the function returns the number of bytes which cannot
  * be copied.
  * If the returned value is equal or less the @n value, the copy_to_user()
  * functions has failed. Otherwise the record doesn't fit into the @to buffer.
  *
  * Note that with only one concurrent reader and one concurrent
  * writer, you don't need extra locking to use these functions.
  */
 static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
 		void __user *to, unsigned int n, unsigned int recsize,
 		unsigned int *total)
 {
 	if (!__builtin_constant_p(recsize))
 		return __kfifo_to_user_generic(fifo, to, n, recsize, total);
 	return __kfifo_to_user_rec(fifo, to, n, recsize, total);
 }

 /*
  * __kfifo_peek_... internal functions for peek into the next fifo record
  * do not call it directly, use kfifo_peek_rec() instead
  */
 extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
 				unsigned int recsize);

 /**
  * kfifo_peek_rec - gets the size of the next FIFO record data
  * @fifo: the fifo to be used.
  * @recsize: size of record field
  *
  * This function returns the size of the next FIFO record in number of bytes
  */
 static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
 	unsigned int recsize)
 {
 	if (!__builtin_constant_p(recsize))
 		return __kfifo_peek_generic(fifo, recsize);
 	if (!recsize)
 		return kfifo_len(fifo);
 	return __kfifo_peek_n(fifo, recsize);
 }

 /*
  * __kfifo_skip_... internal functions for skip the next fifo record
  * do not call it directly, use kfifo_skip_rec() instead
  */
 extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);

 static inline void __kfifo_skip_rec(struct kfifo *fifo,
 	unsigned int recsize)
 {
 	unsigned int l;

 	if (recsize) {
 		l = __kfifo_peek_n(fifo, recsize);

 		if (l + recsize <= kfifo_len(fifo)) {
 			__kfifo_add_out(fifo, l + recsize);
 			return;
 		}
 	}
 	kfifo_reset_out(fifo);
 }

 /**
  * kfifo_skip_rec - skip the next fifo out record
  * @fifo: the fifo to be used.
  * @recsize: size of record field
  *
  * This function skips the next FIFO record
  */
 static inline void kfifo_skip_rec(struct kfifo *fifo,
 	unsigned int recsize)
 {
 	if (!__builtin_constant_p(recsize))
 		__kfifo_skip_generic(fifo, recsize);
 	else
 		__kfifo_skip_rec(fifo, recsize);
 }

 /**
  * kfifo_avail_rec - returns the number of bytes available in a record FIFO
  * @fifo: the fifo to be used.
  * @recsize: size of record field
  */
 static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
 	unsigned int recsize)
 {
 	unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);

 	return (l > recsize) ? l - recsize : 0;
 }

 #endif
	/*
	* A generic kernel FIFO implementation.
	*
	* Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
	* Copyright (C) 2004 Stelian Pop <stelian@popies.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.
	*
	*/

	/*
	* Howto 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_locked and kfifo_get
	* into kfifo_out_locked
	* Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc
	* must be passed now to the kfifo_in_locked and kfifo_out_locked
	* as the last parameter.
	* - All formerly name __kfifo_* functions has been renamed into kfifo_*
	*/

	#ifndef _LINUX_KFIFO_H
	#define _LINUX_KFIFO_H

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

	struct kfifo {
	unsigned char buffer; / the buffer holding the data */
	unsigned int size; /* the size of the allocated buffer */
	unsigned int in; /* data is added at offset (in % size) */
	unsigned int out; /* data is extracted from off. (out % size) */
	};

	/*
	* Macros for declaration and initialization of the kfifo datatype
	*/

	/* helper macro */
	#define __kfifo_initializer(s, b) \
	(struct kfifo) { \
	.size = s, \
	.in = 0, \
	.out = 0, \
	.buffer = b \
	}

	/**
	* DECLARE_KFIFO - macro to declare a kfifo and the associated buffer
	* @name: name of the declared kfifo datatype
	* @size: size of the fifo buffer. Must be a power of two.
	*
	* Note1: the macro can be used inside struct or union declaration
	* Note2: the macro creates two objects:
	* A kfifo object with the given name and a buffer for the kfifo
	* object named name##kfifo_buffer
	*/
	#define DECLARE_KFIFO(name, size) \
	union { \
	struct kfifo name; \
	unsigned char name##kfifo_buffer[size + sizeof(struct kfifo)]; \
	}

	/**
	* INIT_KFIFO - Initialize a kfifo declared by DECLARE_KFIFO
	* @name: name of the declared kfifo datatype
	*/
	#define INIT_KFIFO(name) \
	name = __kfifo_initializer(sizeof(name##kfifo_buffer) - \
	sizeof(struct kfifo), \
	name##kfifo_buffer + sizeof(struct kfifo))

	/**
	* DEFINE_KFIFO - macro to define and initialize a kfifo
	* @name: name of the declared kfifo datatype
	* @size: size of the fifo buffer. Must be a power of two.
	*
	* Note1: the macro can be used for global and local kfifo data type variables
	* Note2: the macro creates two objects:
	* A kfifo object with the given name and a buffer for the kfifo
	* object named name##kfifo_buffer
	*/
	#define DEFINE_KFIFO(name, size) \
	unsigned char name##kfifo_buffer[size]; \
	struct kfifo name = __kfifo_initializer(size, name##kfifo_buffer)

	extern void kfifo_init(struct kfifo fifo, void buffer,
	unsigned int size);
	extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
	gfp_t gfp_mask);
	extern void kfifo_free(struct kfifo *fifo);
	extern unsigned int kfifo_in(struct kfifo *fifo,
	const void *from, unsigned int len);
	extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
	void *to, unsigned int len);
	extern __must_check unsigned int kfifo_out_peek(struct kfifo *fifo,
	void *to, unsigned int len, unsigned offset);

	/**
	* kfifo_initialized - Check if kfifo is initialized.
	* @fifo: fifo to check
	* Return %true if FIFO is initialized, otherwise %false.
	* Assumes the fifo was 0 before.
	*/
	static inline bool kfifo_initialized(struct kfifo *fifo)
	{
	return fifo->buffer != NULL;
	}

	/**
	* kfifo_reset - removes the entire FIFO contents
	* @fifo: the fifo to be emptied.
	*/
	static inline void kfifo_reset(struct kfifo *fifo)
	{
	fifo->in = fifo->out = 0;
	}

	/**
	* kfifo_reset_out - skip FIFO contents
	* @fifo: the fifo to be emptied.
	*/
	static inline void kfifo_reset_out(struct kfifo *fifo)
	{
	smp_mb();
	fifo->out = fifo->in;
	}

	/**
	* kfifo_size - returns the size of the fifo in bytes
	* @fifo: the fifo to be used.
	*/
	static inline __must_check unsigned int kfifo_size(struct kfifo *fifo)
	{
	return fifo->size;
	}

	/**
	* kfifo_len - returns the number of used bytes in the FIFO
	* @fifo: the fifo to be used.
	*/
	static inline unsigned int kfifo_len(struct kfifo *fifo)
	{
	register unsigned int out;

	out = fifo->out;
	smp_rmb();
	return fifo->in - out;
	}

	/**
	* kfifo_is_empty - returns true if the fifo is empty
	* @fifo: the fifo to be used.
	*/
	static inline __must_check int kfifo_is_empty(struct kfifo *fifo)
	{
	return fifo->in == fifo->out;
	}

	/**
	* kfifo_is_full - returns true if the fifo is full
	* @fifo: the fifo to be used.
	*/
	static inline __must_check int kfifo_is_full(struct kfifo *fifo)
	{
	return kfifo_len(fifo) == kfifo_size(fifo);
	}

	/**
	* kfifo_avail - returns the number of bytes available in the FIFO
	* @fifo: the fifo to be used.
	*/
	static inline __must_check unsigned int kfifo_avail(struct kfifo *fifo)
	{
	return kfifo_size(fifo) - kfifo_len(fifo);
	}

	/**
	* kfifo_in_locked - puts some data into the FIFO using a spinlock for locking
	* @fifo: the fifo to be used.
	* @from: the data to be added.
	* @n: the length of the data to be added.
	* @lock: pointer to the spinlock to use for locking.
	*
	* This function copies at most @n bytes from the @from buffer into
	* the FIFO depending on the free space, and returns the number of
	* bytes copied.
	*/
	static inline unsigned int kfifo_in_locked(struct kfifo *fifo,
	const void from, unsigned int n, spinlock_t lock)
	{
	unsigned long flags;
	unsigned int ret;

	spin_lock_irqsave(lock, flags);

	ret = kfifo_in(fifo, from, n);

	spin_unlock_irqrestore(lock, flags);

	return ret;
	}

	/**
	* kfifo_out_locked - gets some data from the FIFO using a spinlock for locking
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @n: the size of the destination buffer.
	* @lock: pointer to the spinlock to use for locking.
	*
	* This function copies at most @n bytes from the FIFO into the
	* @to buffer and returns the number of copied bytes.
	*/
	static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
	void to, unsigned int n, spinlock_t lock)
	{
	unsigned long flags;
	unsigned int ret;

	spin_lock_irqsave(lock, flags);

	ret = kfifo_out(fifo, to, n);

	spin_unlock_irqrestore(lock, flags);

	return ret;
	}

	extern void kfifo_skip(struct kfifo *fifo, unsigned int len);

	extern __must_check int kfifo_from_user(struct kfifo *fifo,
	const void __user from, unsigned int n, unsigned lenout);

	extern __must_check int kfifo_to_user(struct kfifo *fifo,
	void __user to, unsigned int n, unsigned lenout);

	/*
	* __kfifo_add_out internal helper function for updating the out offset
	*/
	static inline void __kfifo_add_out(struct kfifo *fifo,
	unsigned int off)
	{
	smp_mb();
	fifo->out += off;
	}

	/*
	* __kfifo_add_in internal helper function for updating the in offset
	*/
	static inline void __kfifo_add_in(struct kfifo *fifo,
	unsigned int off)
	{
	smp_wmb();
	fifo->in += off;
	}

	/*
	* __kfifo_off internal helper function for calculating the index of a
	* given offeset
	*/
	static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
	{
	return off & (fifo->size - 1);
	}

	/*
	* __kfifo_peek_n internal helper function for determinate the length of
	* the next record in the fifo
	*/
	static inline unsigned int __kfifo_peek_n(struct kfifo *fifo,
	unsigned int recsize)
	{
	#define __KFIFO_GET(fifo, off, shift) \
	((fifo)->buffer[__kfifo_off((fifo), (fifo)->out+(off))] << (shift))

	unsigned int l;

	l = __KFIFO_GET(fifo, 0, 0);

	if (--recsize)
	l \|= __KFIFO_GET(fifo, 1, 8);

	return l;
	#undef __KFIFO_GET
	}

	/*
	* __kfifo_poke_n internal helper function for storing the length of
	* the next record into the fifo
	*/
	static inline void __kfifo_poke_n(struct kfifo *fifo,
	unsigned int recsize, unsigned int n)
	{
	#define __KFIFO_PUT(fifo, off, val, shift) \
	( \
	(fifo)->buffer[__kfifo_off((fifo), (fifo)->in+(off))] = \
	(unsigned char)((val) >> (shift)) \
	)

	__KFIFO_PUT(fifo, 0, n, 0);

	if (--recsize)
	__KFIFO_PUT(fifo, 1, n, 8);
	#undef __KFIFO_PUT
	}

	/*
	* __kfifo_in_... internal functions for put date into the fifo
	* do not call it directly, use kfifo_in_rec() instead
	*/
	extern unsigned int __kfifo_in_n(struct kfifo *fifo,
	const void *from, unsigned int n, unsigned int recsize);

	extern unsigned int __kfifo_in_generic(struct kfifo *fifo,
	const void *from, unsigned int n, unsigned int recsize);

	static inline unsigned int __kfifo_in_rec(struct kfifo *fifo,
	const void *from, unsigned int n, unsigned int recsize)
	{
	unsigned int ret;

	ret = __kfifo_in_n(fifo, from, n, recsize);

	if (likely(ret == 0)) {
	if (recsize)
	__kfifo_poke_n(fifo, recsize, n);
	__kfifo_add_in(fifo, n + recsize);
	}
	return ret;
	}

	/**
	* kfifo_in_rec - puts some record data into the FIFO
	* @fifo: the fifo to be used.
	* @from: the data to be added.
	* @n: the length of the data to be added.
	* @recsize: size of record field
	*
	* This function copies @n bytes from the @from into the FIFO and returns
	* the number of bytes which cannot be copied.
	* A returned value greater than the @n value means that the record doesn't
	* fit into the buffer.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	static inline __must_check unsigned int kfifo_in_rec(struct kfifo *fifo,
	void *from, unsigned int n, unsigned int recsize)
	{
	if (!__builtin_constant_p(recsize))
	return __kfifo_in_generic(fifo, from, n, recsize);
	return __kfifo_in_rec(fifo, from, n, recsize);
	}

	/*
	* __kfifo_out_... internal functions for get date from the fifo
	* do not call it directly, use kfifo_out_rec() instead
	*/
	extern unsigned int __kfifo_out_n(struct kfifo *fifo,
	void *to, unsigned int reclen, unsigned int recsize);

	extern unsigned int __kfifo_out_generic(struct kfifo *fifo,
	void *to, unsigned int n,
	unsigned int recsize, unsigned int *total);

	static inline unsigned int __kfifo_out_rec(struct kfifo *fifo,
	void *to, unsigned int n, unsigned int recsize,
	unsigned int *total)
	{
	unsigned int l;

	if (!recsize) {
	l = n;
	if (total)
	*total = l;
	} else {
	l = __kfifo_peek_n(fifo, recsize);
	if (total)
	*total = l;
	if (n < l)
	return l;
	}

	return __kfifo_out_n(fifo, to, l, recsize);
	}

	/**
	* kfifo_out_rec - gets some record data from the FIFO
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @n: the size of the destination buffer.
	* @recsize: size of record field
	* @total: pointer where the total number of to copied bytes should stored
	*
	* This function copies at most @n bytes from the FIFO to @to and returns the
	* number of bytes which cannot be copied.
	* A returned value greater than the @n value means that the record doesn't
	* fit into the @to buffer.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	static inline __must_check unsigned int kfifo_out_rec(struct kfifo *fifo,
	void *to, unsigned int n, unsigned int recsize,
	unsigned int *total)

	{
	if (!__builtin_constant_p(recsize))
	return __kfifo_out_generic(fifo, to, n, recsize, total);
	return __kfifo_out_rec(fifo, to, n, recsize, total);
	}

	/*
	* __kfifo_from_user_... internal functions for transfer from user space into
	* the fifo. do not call it directly, use kfifo_from_user_rec() instead
	*/
	extern unsigned int __kfifo_from_user_n(struct kfifo *fifo,
	const void __user *from, unsigned int n, unsigned int recsize);

	extern unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
	const void __user *from, unsigned int n, unsigned int recsize);

	static inline unsigned int __kfifo_from_user_rec(struct kfifo *fifo,
	const void __user *from, unsigned int n, unsigned int recsize)
	{
	unsigned int ret;

	ret = __kfifo_from_user_n(fifo, from, n, recsize);

	if (likely(ret == 0)) {
	if (recsize)
	__kfifo_poke_n(fifo, recsize, n);
	__kfifo_add_in(fifo, n + recsize);
	}
	return ret;
	}

	/**
	* kfifo_from_user_rec - puts some data from user space into the FIFO
	* @fifo: the fifo to be used.
	* @from: pointer to the data to be added.
	* @n: the length of the data to be added.
	* @recsize: size of record field
	*
	* This function copies @n bytes from the @from into the
	* FIFO and returns the number of bytes which cannot be copied.
	*
	* If the returned value is equal or less the @n value, the copy_from_user()
	* functions has failed. Otherwise the record doesn't fit into the buffer.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	static inline __must_check unsigned int kfifo_from_user_rec(struct kfifo *fifo,
	const void __user *from, unsigned int n, unsigned int recsize)
	{
	if (!__builtin_constant_p(recsize))
	return __kfifo_from_user_generic(fifo, from, n, recsize);
	return __kfifo_from_user_rec(fifo, from, n, recsize);
	}

	/*
	* __kfifo_to_user_... internal functions for transfer fifo data into user space
	* do not call it directly, use kfifo_to_user_rec() instead
	*/
	extern unsigned int __kfifo_to_user_n(struct kfifo *fifo,
	void __user *to, unsigned int n, unsigned int reclen,
	unsigned int recsize);

	extern unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
	void __user *to, unsigned int n, unsigned int recsize,
	unsigned int *total);

	static inline unsigned int __kfifo_to_user_rec(struct kfifo *fifo,
	void __user *to, unsigned int n,
	unsigned int recsize, unsigned int *total)
	{
	unsigned int l;

	if (!recsize) {
	l = n;
	if (total)
	*total = l;
	} else {
	l = __kfifo_peek_n(fifo, recsize);
	if (total)
	*total = l;
	if (n < l)
	return l;
	}

	return __kfifo_to_user_n(fifo, to, n, l, recsize);
	}

	/**
	* kfifo_to_user_rec - gets data from the FIFO and write it to user space
	* @fifo: the fifo to be used.
	* @to: where the data must be copied.
	* @n: the size of the destination buffer.
	* @recsize: size of record field
	* @total: pointer where the total number of to copied bytes should stored
	*
	* This function copies at most @n bytes from the FIFO to the @to.
	* In case of an error, the function returns the number of bytes which cannot
	* be copied.
	* If the returned value is equal or less the @n value, the copy_to_user()
	* functions has failed. Otherwise the record doesn't fit into the @to buffer.
	*
	* Note that with only one concurrent reader and one concurrent
	* writer, you don't need extra locking to use these functions.
	*/
	static inline __must_check unsigned int kfifo_to_user_rec(struct kfifo *fifo,
	void __user *to, unsigned int n, unsigned int recsize,
	unsigned int *total)
	{
	if (!__builtin_constant_p(recsize))
	return __kfifo_to_user_generic(fifo, to, n, recsize, total);
	return __kfifo_to_user_rec(fifo, to, n, recsize, total);
	}

	/*
	* __kfifo_peek_... internal functions for peek into the next fifo record
	* do not call it directly, use kfifo_peek_rec() instead
	*/
	extern unsigned int __kfifo_peek_generic(struct kfifo *fifo,
	unsigned int recsize);

	/**
	* kfifo_peek_rec - gets the size of the next FIFO record data
	* @fifo: the fifo to be used.
	* @recsize: size of record field
	*
	* This function returns the size of the next FIFO record in number of bytes
	*/
	static inline __must_check unsigned int kfifo_peek_rec(struct kfifo *fifo,
	unsigned int recsize)
	{
	if (!__builtin_constant_p(recsize))
	return __kfifo_peek_generic(fifo, recsize);
	if (!recsize)
	return kfifo_len(fifo);
	return __kfifo_peek_n(fifo, recsize);
	}

	/*
	* __kfifo_skip_... internal functions for skip the next fifo record
	* do not call it directly, use kfifo_skip_rec() instead
	*/
	extern void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize);

	static inline void __kfifo_skip_rec(struct kfifo *fifo,
	unsigned int recsize)
	{
	unsigned int l;

	if (recsize) {
	l = __kfifo_peek_n(fifo, recsize);

	if (l + recsize <= kfifo_len(fifo)) {
	__kfifo_add_out(fifo, l + recsize);
	return;
	}
	}
	kfifo_reset_out(fifo);
	}

	/**
	* kfifo_skip_rec - skip the next fifo out record
	* @fifo: the fifo to be used.
	* @recsize: size of record field
	*
	* This function skips the next FIFO record
	*/
	static inline void kfifo_skip_rec(struct kfifo *fifo,
	unsigned int recsize)
	{
	if (!__builtin_constant_p(recsize))
	__kfifo_skip_generic(fifo, recsize);
	else
	__kfifo_skip_rec(fifo, recsize);
	}

	/**
	* kfifo_avail_rec - returns the number of bytes available in a record FIFO
	* @fifo: the fifo to be used.
	* @recsize: size of record field
	*/
	static inline __must_check unsigned int kfifo_avail_rec(struct kfifo *fifo,
	unsigned int recsize)
	{
	unsigned int l = kfifo_size(fifo) - kfifo_len(fifo);

	return (l > recsize) ? l - recsize : 0;
	}

	#endif