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/*

 * A simple kernel FIFO implementation.

 *

 * 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>

/**

 * kfifo_init - allocates a new FIFO using a preallocated buffer

 * @buffer: the preallocated buffer to be used.

 * @size: the size of the internal buffer, this have to be a power of 2.

 * @gfp_mask: get_free_pages mask, passed to kmalloc()

 * @lock: the lock to be used to protect the fifo buffer

 *

 * Do NOT pass the kfifo to kfifo_free() after use! Simply free the

 * &struct kfifo with kfree().

 */

struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,

                         gfp_t gfp_mask, spinlock_t *lock)

{

        struct kfifo *fifo;

        /* size must be a power of 2 */

        BUG_ON(!is_power_of_2(size));

        fifo = kmalloc(sizeof(struct kfifo), gfp_mask);

        if (!fifo)

                return ERR_PTR(-ENOMEM);

        fifo->buffer = buffer;

        fifo->size = size;

        fifo->in = fifo->out = 0;

        fifo->lock = lock;

        return fifo;

}

EXPORT_SYMBOL(kfifo_init);

/**

 * kfifo_alloc - allocates a new FIFO and its internal buffer

 * @size: the size of the internal buffer to be allocated.

 * @gfp_mask: get_free_pages mask, passed to kmalloc()

 * @lock: the lock to be used to protect the fifo buffer

 *

 * The size will be rounded-up to a power of 2.

 */

struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, spinlock_t *lock)

{

        unsigned char *buffer;

        struct kfifo *ret;

        /*

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

         * wrap' tachnique works only in this case.

         */

        if (size & (size - 1)) {

                BUG_ON(size > 0x80000000);

                size = roundup_pow_of_two(size);

        }

        buffer = kmalloc(size, gfp_mask);

        if (!buffer)

                return ERR_PTR(-ENOMEM);

        ret = kfifo_init(buffer, size, gfp_mask, lock);

        if (IS_ERR(ret))

                kfree(buffer);

        return ret;

}

EXPORT_SYMBOL(kfifo_alloc);

/**

 * kfifo_free - frees the FIFO

 * @fifo: the fifo to be freed.

 */

void kfifo_free(struct kfifo *fifo)

{

        kfree(fifo->buffer);

        kfree(fifo);

}

EXPORT_SYMBOL(kfifo_free);

/**

 * __kfifo_put - puts some data into the FIFO, no locking version

 * @fifo: the fifo to be used.

 * @buffer: the data to be added.

 * @len: the length of the data to be added.

 *

 * This function copies at most @len bytes from the @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_put(struct kfifo *fifo,

                         unsigned char *buffer, 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)), buffer, l);

        /* then put the rest (if any) at the beginning of the buffer */

        memcpy(fifo->buffer, buffer + 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_put);

/**

 * __kfifo_get - gets some data from the FIFO, no locking version

 * @fifo: the fifo to be used.

 * @buffer: 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

 * @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_get(struct kfifo *fifo,

                         unsigned char *buffer, 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(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);

        /* then get the rest (if any) from the beginning of the buffer */

        memcpy(buffer + 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_get);