/*

   * 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/export.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) {

  			sg_set_page(sgl, page, l - off, off);
  			sgl = sg_next(sgl);
  			if (++n == nents || sgl == NULL)

  				return n;
  			page = npage;
  			len -= l - off;
  			l = off = 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);

  	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);

  void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize)
  {
  	unsigned int n;
  
  	n = __kfifo_peek_n(fifo, recsize);
  	fifo->out += n + recsize;
  }
  EXPORT_SYMBOL(__kfifo_skip_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);