/*
 * 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>
#include <linux/uaccess.h>

static void _kfifo_init(struct kfifo *fifo, void *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 has to be a power of 2.
 *
 */
void kfifo_init(struct kfifo *fifo, void *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, NULL, 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);
        _kfifo_init(fifo, NULL, 0);
}
EXPORT_SYMBOL(kfifo_free);

/**
 * kfifo_skip - skip output data
 * @fifo: the fifo to be used.
 * @len: number of bytes to skip
 */
void kfifo_skip(struct kfifo *fifo, unsigned int len)
{
        if (len < kfifo_len(fifo)) {
                __kfifo_add_out(fifo, len);
                return;
        }
        kfifo_reset_out(fifo);
}
EXPORT_SYMBOL(kfifo_skip);

static inline void __kfifo_in_data(struct kfifo *fifo,
                const void *from, unsigned int len, unsigned int off)
{
        unsigned int l;

        /*
         * Ensure that we sample the fifo->out index -before- we
         * start putting bytes into the kfifo.
         */

        smp_mb();

        off = __kfifo_off(fifo, fifo->in + off);

        /* first put the data starting from fifo->in to buffer end */
        l = min(len, fifo->size - off);
        memcpy(fifo->buffer + off, from, l);

        /* then put the rest (if any) at the beginning of the buffer */
        memcpy(fifo->buffer, from + l, len - l);
}

static inline void __kfifo_out_data(struct kfifo *fifo,
                void *to, unsigned int len, unsigned int off)
{
        unsigned int l;

        /*
         * Ensure that we sample the fifo->in index -before- we
         * start removing bytes from the kfifo.
         */

        smp_rmb();

        off = __kfifo_off(fifo, fifo->out + off);

        /* first get the data from fifo->out until the end of the buffer */
        l = min(len, fifo->size - off);
        memcpy(to, fifo->buffer + off, l);

        /* then get the rest (if any) from the beginning of the buffer */
        memcpy(to + l, fifo->buffer, len - l);
}

static inline int __kfifo_from_user_data(struct kfifo *fifo,
         const void __user *from, unsigned int len, unsigned int off,
         unsigned *lenout)
{
        unsigned int l;
        int ret;

        /*
         * Ensure that we sample the fifo->out index -before- we
         * start putting bytes into the kfifo.
         */

        smp_mb();

        off = __kfifo_off(fifo, fifo->in + off);

        /* first put the data starting from fifo->in to buffer end */
        l = min(len, fifo->size - off);
        ret = copy_from_user(fifo->buffer + off, from, l);
        if (unlikely(ret)) {
                *lenout = ret;
                return -EFAULT;
        }
        *lenout = l;

        /* then put the rest (if any) at the beginning of the buffer */
        ret = copy_from_user(fifo->buffer, from + l, len - l);
        *lenout += ret ? ret : len - l;
        return ret ? -EFAULT : 0;
}

static inline int __kfifo_to_user_data(struct kfifo *fifo,
                void __user *to, unsigned int len, unsigned int off, unsigned *lenout)
{
        unsigned int l;
        int ret;

        /*
         * Ensure that we sample the fifo->in index -before- we
         * start removing bytes from the kfifo.
         */

        smp_rmb();

        off = __kfifo_off(fifo, fifo->out + off);

        /* first get the data from fifo->out until the end of the buffer */
        l = min(len, fifo->size - off);
        ret = copy_to_user(to, fifo->buffer + off, l);
        *lenout = l;
        if (unlikely(ret)) {
                *lenout -= ret;
                return -EFAULT;
        }

        /* then get the rest (if any) from the beginning of the buffer */
        len -= l;
        ret = copy_to_user(to + l, fifo->buffer, len);
        if (unlikely(ret)) {
                *lenout += len - ret;
                return -EFAULT;
        }
        *lenout += len;
        return 0;
}

unsigned int __kfifo_in_n(struct kfifo *fifo,
        const void *from, unsigned int len, unsigned int recsize)
{
        if (kfifo_avail(fifo) < len + recsize)
                return len + 1;

        __kfifo_in_data(fifo, from, len, recsize);
        return 0;
}
EXPORT_SYMBOL(__kfifo_in_n);

/**
 * 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 void *from,
                                unsigned int len)
{
        len = min(kfifo_avail(fifo), len);

        __kfifo_in_data(fifo, from, len, 0);
        __kfifo_add_in(fifo, len);
        return len;
}
EXPORT_SYMBOL(kfifo_in);

unsigned int __kfifo_in_generic(struct kfifo *fifo,
        const void *from, unsigned int len, unsigned int recsize)
{
        return __kfifo_in_rec(fifo, from, len, recsize);
}
EXPORT_SYMBOL(__kfifo_in_generic);

unsigned int __kfifo_out_n(struct kfifo *fifo,
        void *to, unsigned int len, unsigned int recsize)
{
        if (kfifo_len(fifo) < len + recsize)
                return len;

        __kfifo_out_data(fifo, to, len, recsize);
        __kfifo_add_out(fifo, len + recsize);
        return 0;
}
EXPORT_SYMBOL(__kfifo_out_n);

/**
 * 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, void *to, unsigned int len)
{
        len = min(kfifo_len(fifo), len);

        __kfifo_out_data(fifo, to, len, 0);
        __kfifo_add_out(fifo, len);

        return len;
}
EXPORT_SYMBOL(kfifo_out);

/**
 * kfifo_out_peek - copy some data from the FIFO, but do not remove it
 * @fifo: the fifo to be used.
 * @to: where the data must be copied.
 * @len: the size of the destination buffer.
 * @offset: offset into the fifo
 *
 * This function copies at most @len bytes at @offset from the FIFO
 * into the @to buffer and returns the number of copied bytes.
 * The data is not removed from the FIFO.
 */
unsigned int kfifo_out_peek(struct kfifo *fifo, void *to, unsigned int len,
                            unsigned offset)
{
        len = min(kfifo_len(fifo), len + offset);

        __kfifo_out_data(fifo, to, len, offset);
        return len;
}
EXPORT_SYMBOL(kfifo_out_peek);

unsigned int __kfifo_out_generic(struct kfifo *fifo,
        void *to, unsigned int len, unsigned int recsize,
        unsigned int *total)
{
        return __kfifo_out_rec(fifo, to, len, recsize, total);
}
EXPORT_SYMBOL(__kfifo_out_generic);

unsigned int __kfifo_from_user_n(struct kfifo *fifo,
        const void __user *from, unsigned int len, unsigned int recsize)
{
        unsigned total;

        if (kfifo_avail(fifo) < len + recsize)
                return len + 1;

        __kfifo_from_user_data(fifo, from, len, recsize, &total);
        return total;
}
EXPORT_SYMBOL(__kfifo_from_user_n);

/**
 * kfifo_from_user - puts some data from user space into the FIFO
 * @fifo: the fifo to be used.
 * @from: pointer to the data to be added.
 * @len: the length of the data to be added.
 * @total: the actual returned data length.
 *
 * This function copies at most @len bytes from the @from into the
 * FIFO depending and returns -EFAULT/0.
 *
 * Note that with only one concurrent reader and one concurrent
 * writer, you don't need extra locking to use these functions.
 */
int kfifo_from_user(struct kfifo *fifo,
        const void __user *from, unsigned int len, unsigned *total)
{
        int ret;
        len = min(kfifo_avail(fifo), len);
        ret = __kfifo_from_user_data(fifo, from, len, 0, total);
        if (ret)
                return ret;
        __kfifo_add_in(fifo, len);
        return 0;
}
EXPORT_SYMBOL(kfifo_from_user);

unsigned int __kfifo_from_user_generic(struct kfifo *fifo,
        const void __user *from, unsigned int len, unsigned int recsize)
{
        return __kfifo_from_user_rec(fifo, from, len, recsize);
}
EXPORT_SYMBOL(__kfifo_from_user_generic);

unsigned int __kfifo_to_user_n(struct kfifo *fifo,
        void __user *to, unsigned int len, unsigned int reclen,
        unsigned int recsize)
{
        unsigned int ret, total;

        if (kfifo_len(fifo) < reclen + recsize)
                return len;

        ret = __kfifo_to_user_data(fifo, to, reclen, recsize, &total);

        if (likely(ret == 0))
                __kfifo_add_out(fifo, reclen + recsize);

        return total;
}
EXPORT_SYMBOL(__kfifo_to_user_n);

/**
 * kfifo_to_user - gets data from the FIFO and write it to user space
 * @fifo: the fifo to be used.
 * @to: where the data must be copied.
 * @len: the size of the destination buffer.
 * @lenout: pointer to output variable with copied data
 *
 * This function copies at most @len bytes from the FIFO into the
 * @to buffer and 0 or -EFAULT.
 *
 * Note that with only one concurrent reader and one concurrent
 * writer, you don't need extra locking to use these functions.
 */
int kfifo_to_user(struct kfifo *fifo,
        void __user *to, unsigned int len, unsigned *lenout)
{
        int ret;
        len = min(kfifo_len(fifo), len);
        ret = __kfifo_to_user_data(fifo, to, len, 0, lenout);
        __kfifo_add_out(fifo, *lenout);
        return ret;
}
EXPORT_SYMBOL(kfifo_to_user);

unsigned int __kfifo_to_user_generic(struct kfifo *fifo,
        void __user *to, unsigned int len, unsigned int recsize,
        unsigned int *total)
{
        return __kfifo_to_user_rec(fifo, to, len, recsize, total);
}
EXPORT_SYMBOL(__kfifo_to_user_generic);

unsigned int __kfifo_peek_generic(struct kfifo *fifo, unsigned int recsize)
{
        if (recsize == 0)
                return kfifo_avail(fifo);

        return __kfifo_peek_n(fifo, recsize);
}
EXPORT_SYMBOL(__kfifo_peek_generic);

void __kfifo_skip_generic(struct kfifo *fifo, unsigned int recsize)
{
        __kfifo_skip_rec(fifo, recsize);
}
EXPORT_SYMBOL(__kfifo_skip_generic);