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Diffstat (limited to 'kernel/kfifo.c')
| -rw-r--r-- | kernel/kfifo.c | 168 |
1 files changed, 168 insertions, 0 deletions
diff --git a/kernel/kfifo.c b/kernel/kfifo.c new file mode 100644 index 000000000000..179baafcdd96 --- /dev/null +++ b/kernel/kfifo.c @@ -0,0 +1,168 @@ +/* + * 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> + +/** + * 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, + unsigned int __nocast gfp_mask, spinlock_t *lock) +{ + struct kfifo *fifo; + + /* size must be a power of 2 */ + BUG_ON(size & (size - 1)); + + 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, unsigned int __nocast 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); + + /* 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); + + 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); + + /* 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); + + fifo->out += len; + + return len; +} +EXPORT_SYMBOL(__kfifo_get); |