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/*
* 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) */
};
extern void kfifo_init(struct kfifo *fifo, unsigned char *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 unsigned char *from, unsigned int len);
extern __must_check unsigned int kfifo_out(struct kfifo *fifo,
unsigned char *to, unsigned int len);
/**
* 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_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_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 @len 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 unsigned char *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 @len 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,
unsigned char *to, unsigned int n, spinlock_t *lock)
{
unsigned long flags;
unsigned int ret;
spin_lock_irqsave(lock, flags);
ret = kfifo_out(fifo, to, n);
/*
* optimization: if the FIFO is empty, set the indices to 0
* so we don't wrap the next time
*/
if (fifo->in == fifo->out)
fifo->in = fifo->out = 0;
spin_unlock_irqrestore(lock, flags);
return ret;
}
#endif
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