kfifo: replace the old non generic API

     <title>FIFO Buffer</title>

     <sect1><title>kfifo interface</title>

!Iinclude/linux/kfifo.h

!Ekernel/kfifo.c

     </sect1>

  </chapter>

/*

 * A generic kernel FIFO implementation

 *

 * Copyright (C) 2009/2010 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.

 *

 */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/slab.h>

#include <linux/err.h>

#include <linux/log2.h>

#include <linux/uaccess.h>

#include <linux/kfifo.h>

/*

 * internal helper to calculate the unused elements in a fifo

 */

static inline unsigned int kfifo_unused(struct __kfifo *fifo)

{

	return (fifo->mask + 1) - (fifo->in - fifo->out);

}

int __kfifo_alloc(struct __kfifo *fifo, unsigned int size,

		size_t esize, gfp_t gfp_mask)

{

	/*

	 * round down to the next power of 2, since our 'let the indices

	 * wrap' technique works only in this case.

	 */

	if (!is_power_of_2(size))

		size = rounddown_pow_of_two(size);

	fifo->in = 0;

	fifo->out = 0;

	fifo->esize = esize;

	if (size < 2) {

		fifo->data = NULL;

		fifo->mask = 0;

		return -EINVAL;

	}

	fifo->data = kmalloc(size * esize, gfp_mask);

	if (!fifo->data) {

		fifo->mask = 0;

		return -ENOMEM;

	}

	fifo->mask = size - 1;

	return 0;

}

EXPORT_SYMBOL(__kfifo_alloc);

void __kfifo_free(struct __kfifo *fifo)

{

	kfree(fifo->data);

	fifo->in = 0;

	fifo->out = 0;

	fifo->esize = 0;

	fifo->data = NULL;

	fifo->mask = 0;

}

EXPORT_SYMBOL(__kfifo_free);

int __kfifo_init(struct __kfifo *fifo, void *buffer,

		unsigned int size, size_t esize)

{

	size /= esize;

	if (!is_power_of_2(size))

		size = rounddown_pow_of_two(size);

	fifo->in = 0;

	fifo->out = 0;

	fifo->esize = esize;

	fifo->data = buffer;

	if (size < 2) {

		fifo->mask = 0;

		return -EINVAL;

	}

	fifo->mask = size - 1;

	return 0;

}

EXPORT_SYMBOL(__kfifo_init);

static void kfifo_copy_in(struct __kfifo *fifo, const void *src,

		unsigned int len, unsigned int off)

{

	unsigned int size = fifo->mask + 1;

	unsigned int esize = fifo->esize;

	unsigned int l;

	off &= fifo->mask;

	if (esize != 1) {

		off *= esize;

		size *= esize;

		len *= esize;

	}

	l = min(len, size - off);

	memcpy(fifo->data + off, src, l);

	memcpy(fifo->data, src + l, len - l);

	/*

	 * make sure that the data in the fifo is up to date before

	 * incrementing the fifo->in index counter

	 */

	smp_wmb();

}

unsigned int __kfifo_in(struct __kfifo *fifo,

		const void *buf, unsigned int len)

{

	unsigned int l;

	l = kfifo_unused(fifo);

	if (len > l)

		len = l;

	kfifo_copy_in(fifo, buf, len, fifo->in);

	fifo->in += len;

	return len;

}

EXPORT_SYMBOL(__kfifo_in);

static void kfifo_copy_out(struct __kfifo *fifo, void *dst,

		unsigned int len, unsigned int off)

{

	unsigned int size = fifo->mask + 1;

	unsigned int esize = fifo->esize;

	unsigned int l;

	off &= fifo->mask;

	if (esize != 1) {

		off *= esize;

		size *= esize;

		len *= esize;

	}

	l = min(len, size - off);

	memcpy(dst, fifo->data + off, l);

	memcpy(dst + l, fifo->data, len - l);

	/*

	 * make sure that the data is copied before

	 * incrementing the fifo->out index counter

	 */

	smp_wmb();

}

unsigned int __kfifo_out_peek(struct __kfifo *fifo,

		void *buf, unsigned int len)

{

	unsigned int l;

	l = fifo->in - fifo->out;

	if (len > l)

		len = l;

	kfifo_copy_out(fifo, buf, len, fifo->out);

	return len;

}

EXPORT_SYMBOL(__kfifo_out_peek);

unsigned int __kfifo_out(struct __kfifo *fifo,

		void *buf, unsigned int len)

{

	len = __kfifo_out_peek(fifo, buf, len);

	fifo->out += len;

	return len;

}

EXPORT_SYMBOL(__kfifo_out);

static unsigned long kfifo_copy_from_user(struct __kfifo *fifo,

	const void __user *from, unsigned int len, unsigned int off,

	unsigned int *copied)

{

	unsigned int size = fifo->mask + 1;

	unsigned int esize = fifo->esize;

	unsigned int l;

	unsigned long ret;

	off &= fifo->mask;

	if (esize != 1) {

		off *= esize;

		size *= esize;

		len *= esize;

	}

	l = min(len, size - off);

	ret = copy_from_user(fifo->data + off, from, l);

	if (unlikely(ret))

		ret = DIV_ROUND_UP(ret + len - l, esize);

	else {

		ret = copy_from_user(fifo->data, from + l, len - l);

		if (unlikely(ret))

			ret = DIV_ROUND_UP(ret, esize);

	}

	/*

	 * make sure that the data in the fifo is up to date before

	 * incrementing the fifo->in index counter

	 */

	smp_wmb();

	*copied = len - ret;

	/* return the number of elements which are not copied */

	return ret;

}

int __kfifo_from_user(struct __kfifo *fifo, const void __user *from,

		unsigned long len, unsigned int *copied)

{

	unsigned int l;

	unsigned long ret;

	unsigned int esize = fifo->esize;

	int err;

	if (esize != 1)

		len /= esize;

	l = kfifo_unused(fifo);

	if (len > l)

		len = l;

	ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied);

	if (unlikely(ret)) {

		len -= ret;

		err = -EFAULT;

	} else

		err = 0;

	fifo->in += len;

	return err;

}

EXPORT_SYMBOL(__kfifo_from_user);

static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void __user *to,

		unsigned int len, unsigned int off, unsigned int *copied)

{

	unsigned int l;

	unsigned long ret;

	unsigned int size = fifo->mask + 1;

	unsigned int esize = fifo->esize;

	off &= fifo->mask;

	if (esize != 1) {

		off *= esize;

		size *= esize;

		len *= esize;

	}

	l = min(len, size - off);

	ret = copy_to_user(to, fifo->data + off, l);

	if (unlikely(ret))

		ret = DIV_ROUND_UP(ret + len - l, esize);

	else {

		ret = copy_to_user(to + l, fifo->data, len - l);

		if (unlikely(ret))

			ret = DIV_ROUND_UP(ret, esize);

	}

	/*

	 * make sure that the data is copied before

	 * incrementing the fifo->out index counter

	 */

	smp_wmb();

	*copied = len - ret;

	/* return the number of elements which are not copied */

	return ret;

}

int __kfifo_to_user(struct __kfifo *fifo, void __user *to,

		unsigned long len, unsigned int *copied)

{

	unsigned int l;

	unsigned long ret;

	unsigned int esize = fifo->esize;

	int err;

	if (esize != 1)

		len /= esize;

	l = fifo->in - fifo->out;

	if (len > l)

		len = l;

	ret = kfifo_copy_to_user(fifo, to, len, fifo->out, copied);

	if (unlikely(ret)) {

		len -= ret;

		err = -EFAULT;

	} else

		err = 0;

	fifo->out += len;

	return err;

}

EXPORT_SYMBOL(__kfifo_to_user);

static int setup_sgl_buf(struct scatterlist *sgl, void *buf,

		int nents, unsigned int len)

{

	int n;

	unsigned int l;

	unsigned int off;

	struct page *page;

	if (!nents)

		return 0;

	if (!len)

		return 0;

	n = 0;

	page = virt_to_page(buf);

	off = offset_in_page(buf);

	l = 0;

	while (len >= l + PAGE_SIZE - off) {

		struct page *npage;

		l += PAGE_SIZE;

		buf += PAGE_SIZE;

		npage = virt_to_page(buf);

		if (page_to_phys(page) != page_to_phys(npage) - l) {

			sgl->page_link = 0;

			sg_set_page(sgl++, page, l - off, off);

			if (++n == nents)

				return n;

			page = npage;

			len -= l - off;

			l = off = 0;

		}

	}

	sgl->page_link = 0;

	sg_set_page(sgl++, page, len, off);

	return n + 1;

}

static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,

		int nents, unsigned int len, unsigned int off)

{

	unsigned int size = fifo->mask + 1;

	unsigned int esize = fifo->esize;

	unsigned int l;

	unsigned int n;

	off &= fifo->mask;

	if (esize != 1) {

		off *= esize;

		size *= esize;

		len *= esize;

	}

	l = min(len, size - off);

	n  = setup_sgl_buf(sgl, fifo->data + off, nents, l);

	n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l);

	if (n)

		sg_mark_end(sgl + n - 1);

	return n;

}

unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo,

		struct scatterlist *sgl, int nents, unsigned int len)

{

	unsigned int l;

	l = kfifo_unused(fifo);

	if (len > l)

		len = l;

	return setup_sgl(fifo, sgl, nents, len, fifo->in);

}

EXPORT_SYMBOL(__kfifo_dma_in_prepare);

unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo,

		struct scatterlist *sgl, int nents, unsigned int len)

{

	unsigned int l;

	l = fifo->in - fifo->out;

	if (len > l)

		len = l;

	return setup_sgl(fifo, sgl, nents, len, fifo->out);

}

EXPORT_SYMBOL(__kfifo_dma_out_prepare);

unsigned int __kfifo_max_r(unsigned int len, size_t recsize)

{

	unsigned int max = (1 << (recsize << 3)) - 1;

	if (len > max)

		return max;

	return len;

}

#define	__KFIFO_PEEK(data, out, mask) \

	((data)[(out) & (mask)])

/*

 * __kfifo_peek_n internal helper function for determinate the length of

 * the next record in the fifo

 */

static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize)

{

	unsigned int l;

	unsigned int mask = fifo->mask;

	unsigned char *data = fifo->data;

	l = __KFIFO_PEEK(data, fifo->out, mask);

	if (--recsize)

		l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8;

	return l;

}

#define	__KFIFO_POKE(data, in, mask, val) \

	( \

	(data)[(in) & (mask)] = (unsigned char)(val) \

	)

/*

 * __kfifo_poke_n internal helper function for storeing the length of

 * the record into the fifo

 */

static void __kfifo_poke_n(struct __kfifo *fifo, unsigned int n, size_t recsize)

{

	unsigned int mask = fifo->mask;

	unsigned char *data = fifo->data;

	__KFIFO_POKE(data, fifo->in, mask, n);

	if (recsize > 1)

		__KFIFO_POKE(data, fifo->in + 1, mask, n >> 8);

}

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

{

	return __kfifo_peek_n(fifo, recsize);

}

EXPORT_SYMBOL(__kfifo_len_r);

unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf,

		unsigned int len, size_t recsize)

{

	if (len + recsize > kfifo_unused(fifo))

		return 0;

	__kfifo_poke_n(fifo, len, recsize);

	kfifo_copy_in(fifo, buf, len, fifo->in + recsize);

	fifo->in += len + recsize;

	return len;

}

EXPORT_SYMBOL(__kfifo_in_r);

static unsigned int kfifo_out_copy_r(struct __kfifo *fifo,

	void *buf, unsigned int len, size_t recsize, unsigned int *n)

{

	*n = __kfifo_peek_n(fifo, recsize);

	if (len > *n)

		len = *n;

	kfifo_copy_out(fifo, buf, len, fifo->out + recsize);

	return len;

}

unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf,

		unsigned int len, size_t recsize)

{

	unsigned int n;

	if (fifo->in == fifo->out)

		return 0;

	return kfifo_out_copy_r(fifo, buf, len, recsize, &n);

}

EXPORT_SYMBOL(__kfifo_out_peek_r);

unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf,

		unsigned int len, size_t recsize)

{

	unsigned int n;

	if (fifo->in == fifo->out)

		return 0;

	len = kfifo_out_copy_r(fifo, buf, len, recsize, &n);

	fifo->out += n + recsize;

	return len;

}

EXPORT_SYMBOL(__kfifo_out_r);

int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from,

	unsigned long len, unsigned int *copied, size_t recsize)

{

	unsigned long ret;

	len = __kfifo_max_r(len, recsize);

	if (len + recsize > kfifo_unused(fifo)) {

		*copied = 0;

		return 0;

	}

	__kfifo_poke_n(fifo, len, recsize);

	ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied);

	if (unlikely(ret)) {

		*copied = 0;

		return -EFAULT;

	}

	fifo->in += len + recsize;

	return 0;

}

EXPORT_SYMBOL(__kfifo_from_user_r);

int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to,

	unsigned long len, unsigned int *copied, size_t recsize)

{

	unsigned long ret;

	unsigned int n;

	if (fifo->in == fifo->out) {

		*copied = 0;

		return 0;

	}

	n = __kfifo_peek_n(fifo, recsize);

	if (len > n)

		len = n;

	ret = kfifo_copy_to_user(fifo, to, len, fifo->out + recsize, copied);

	if (unlikely(ret)) {

		*copied = 0;

		return -EFAULT;

	}

	fifo->out += n + recsize;

	return 0;

}

EXPORT_SYMBOL(__kfifo_to_user_r);

unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo,

	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)

{

	if (!nents)

		BUG();

	len = __kfifo_max_r(len, recsize);

	if (len + recsize > kfifo_unused(fifo))

		return 0;

	return setup_sgl(fifo, sgl, nents, len, fifo->in + recsize);

}

EXPORT_SYMBOL(__kfifo_dma_in_prepare_r);

void __kfifo_dma_in_finish_r(struct __kfifo *fifo,

	unsigned int len, size_t recsize)

{

	len = __kfifo_max_r(len, recsize);

	__kfifo_poke_n(fifo, len, recsize);

	fifo->in += len + recsize;

}

EXPORT_SYMBOL(__kfifo_dma_in_finish_r);

unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo,

	struct scatterlist *sgl, int nents, unsigned int len, size_t recsize)

{

	if (!nents)

		BUG();

	len = __kfifo_max_r(len, recsize);

	if (len + recsize > fifo->in - fifo->out)

		return 0;

	return setup_sgl(fifo, sgl, nents, len, fifo->out + recsize);

}

EXPORT_SYMBOL(__kfifo_dma_out_prepare_r);

void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize)

{

	unsigned int len;

	len = __kfifo_peek_n(fifo, recsize);

	fifo->out += len + recsize;

}

EXPORT_SYMBOL(__kfifo_dma_out_finish_r);