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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.
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/kfifo.h>
#include <linux/log2.h>
static void _kfifo_init(struct kfifo *fifo, unsigned char *buffer,
unsigned int size)
{
fifo->buffer = buffer;
fifo->size = size;
kfifo_reset(fifo);
}
/**
* 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.
*
*/
void kfifo_init(struct kfifo *fifo, unsigned char *buffer, unsigned int size)
{
/* size must be a power of 2 */
BUG_ON(!is_power_of_2(size));
_kfifo_init(fifo, buffer, size);
}
EXPORT_SYMBOL(kfifo_init);
/**
* kfifo_alloc - allocates a new FIFO internal buffer
* @fifo: the fifo to assign then new buffer
* @size: the size of the buffer to be allocated, this have to be a power of 2.
* @gfp_mask: get_free_pages mask, passed to kmalloc()
*
* This function dynamically allocates a new fifo internal buffer
*
* The size will be rounded-up to a power of 2.
* The buffer will be release with kfifo_free().
* Return 0 if no error, otherwise the an error code
*/
int kfifo_alloc(struct kfifo *fifo, unsigned int size, gfp_t gfp_mask)
{
unsigned char *buffer;
/*
* round up to the next power of 2, since our 'let the indices
* wrap' technique works only in this case.
*/
if (!is_power_of_2(size)) {
BUG_ON(size > 0x80000000);
size = roundup_pow_of_two(size);
}
buffer = kmalloc(size, gfp_mask);
if (!buffer) {
_kfifo_init(fifo, 0, 0);
return -ENOMEM;
}
_kfifo_init(fifo, buffer, size);
return 0;
}
EXPORT_SYMBOL(kfifo_alloc);
/**
* kfifo_free - frees the FIFO internal buffer
* @fifo: the fifo to be freed.
*/
void kfifo_free(struct kfifo *fifo)
{
kfree(fifo->buffer);
}
EXPORT_SYMBOL(kfifo_free);
/**
* kfifo_in - puts some data into the FIFO
* @fifo: the fifo to be used.
* @from: the data to be added.
* @len: the length of the data to be added.
*
* 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.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int kfifo_in(struct kfifo *fifo,
const unsigned char *from, unsigned int len)
{
unsigned int l;
len = min(len, fifo->size - fifo->in + fifo->out);
/*
* Ensure that we sample the fifo->out index -before- we
* start putting bytes into the kfifo.
*/
smp_mb();
/* first put the data starting from fifo->in to buffer end */
l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), from, l);
/* then put the rest (if any) at the beginning of the buffer */
memcpy(fifo->buffer, from + l, len - l);
/*
* Ensure that we add the bytes to the kfifo -before-
* we update the fifo->in index.
*/
smp_wmb();
fifo->in += len;
return len;
}
EXPORT_SYMBOL(kfifo_in);
/**
* kfifo_out - gets some data from the FIFO
* @fifo: the fifo to be used.
* @to: where the data must be copied.
* @len: the size of the destination buffer.
*
* This function copies at most @len bytes from the FIFO into the
* @to buffer and returns the number of copied bytes.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int kfifo_out(struct kfifo *fifo,
unsigned char *to, unsigned int len)
{
unsigned int l;
len = min(len, fifo->in - fifo->out);
/*
* Ensure that we sample the fifo->in index -before- we
* start removing bytes from the kfifo.
*/
smp_rmb();
/* first get the data from fifo->out until the end of the buffer */
l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
memcpy(to, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
/* then get the rest (if any) from the beginning of the buffer */
memcpy(to + l, fifo->buffer, len - l);
/*
* Ensure that we remove the bytes from the kfifo -before-
* we update the fifo->out index.
*/
smp_mb();
fifo->out += len;
return len;
}
EXPORT_SYMBOL(kfifo_out);
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