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![vignesh babu](/assets/img/avatar_default.png)
Replace (n & (n-1)) with is_power_of_2() Signed-off-by: vignesh babu <vignesh.babu@wipro.com> Acked-by: Stelian Pop <stelian@popies.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
197 lines
5.1 KiB
C
197 lines
5.1 KiB
C
/*
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* A simple kernel FIFO implementation.
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*
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* Copyright (C) 2004 Stelian Pop <stelian@popies.net>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/err.h>
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#include <linux/kfifo.h>
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#include <linux/log2.h>
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/**
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* kfifo_init - allocates a new FIFO using a preallocated buffer
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* @buffer: the preallocated buffer to be used.
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* @size: the size of the internal buffer, this have to be a power of 2.
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* @gfp_mask: get_free_pages mask, passed to kmalloc()
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* @lock: the lock to be used to protect the fifo buffer
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*
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* Do NOT pass the kfifo to kfifo_free() after use! Simply free the
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* &struct kfifo with kfree().
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*/
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struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
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gfp_t gfp_mask, spinlock_t *lock)
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{
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struct kfifo *fifo;
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/* size must be a power of 2 */
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BUG_ON(!is_power_of_2(size));
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fifo = kmalloc(sizeof(struct kfifo), gfp_mask);
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if (!fifo)
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return ERR_PTR(-ENOMEM);
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fifo->buffer = buffer;
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fifo->size = size;
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fifo->in = fifo->out = 0;
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fifo->lock = lock;
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return fifo;
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}
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EXPORT_SYMBOL(kfifo_init);
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/**
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* kfifo_alloc - allocates a new FIFO and its internal buffer
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* @size: the size of the internal buffer to be allocated.
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* @gfp_mask: get_free_pages mask, passed to kmalloc()
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* @lock: the lock to be used to protect the fifo buffer
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*
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* The size will be rounded-up to a power of 2.
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*/
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struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, spinlock_t *lock)
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{
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unsigned char *buffer;
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struct kfifo *ret;
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/*
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* round up to the next power of 2, since our 'let the indices
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* wrap' tachnique works only in this case.
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*/
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if (size & (size - 1)) {
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BUG_ON(size > 0x80000000);
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size = roundup_pow_of_two(size);
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}
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buffer = kmalloc(size, gfp_mask);
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if (!buffer)
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return ERR_PTR(-ENOMEM);
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ret = kfifo_init(buffer, size, gfp_mask, lock);
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if (IS_ERR(ret))
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kfree(buffer);
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return ret;
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}
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EXPORT_SYMBOL(kfifo_alloc);
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/**
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* kfifo_free - frees the FIFO
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* @fifo: the fifo to be freed.
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*/
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void kfifo_free(struct kfifo *fifo)
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{
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kfree(fifo->buffer);
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kfree(fifo);
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}
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EXPORT_SYMBOL(kfifo_free);
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/**
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* __kfifo_put - puts some data into the FIFO, no locking version
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* @fifo: the fifo to be used.
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* @buffer: the data to be added.
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* @len: the length of the data to be added.
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*
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* This function copies at most @len bytes from the @buffer into
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* the FIFO depending on the free space, and returns the number of
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* bytes copied.
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*
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* Note that with only one concurrent reader and one concurrent
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* writer, you don't need extra locking to use these functions.
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*/
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unsigned int __kfifo_put(struct kfifo *fifo,
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unsigned char *buffer, unsigned int len)
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{
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unsigned int l;
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len = min(len, fifo->size - fifo->in + fifo->out);
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/*
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* Ensure that we sample the fifo->out index -before- we
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* start putting bytes into the kfifo.
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*/
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smp_mb();
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/* first put the data starting from fifo->in to buffer end */
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l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
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memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), buffer, l);
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/* then put the rest (if any) at the beginning of the buffer */
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memcpy(fifo->buffer, buffer + l, len - l);
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/*
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* Ensure that we add the bytes to the kfifo -before-
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* we update the fifo->in index.
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*/
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smp_wmb();
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fifo->in += len;
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return len;
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}
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EXPORT_SYMBOL(__kfifo_put);
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/**
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* __kfifo_get - gets some data from the FIFO, no locking version
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* @fifo: the fifo to be used.
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* @buffer: where the data must be copied.
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* @len: the size of the destination buffer.
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*
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* This function copies at most @len bytes from the FIFO into the
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* @buffer and returns the number of copied bytes.
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*
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* Note that with only one concurrent reader and one concurrent
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* writer, you don't need extra locking to use these functions.
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*/
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unsigned int __kfifo_get(struct kfifo *fifo,
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unsigned char *buffer, unsigned int len)
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{
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unsigned int l;
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len = min(len, fifo->in - fifo->out);
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/*
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* Ensure that we sample the fifo->in index -before- we
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* start removing bytes from the kfifo.
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*/
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smp_rmb();
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/* first get the data from fifo->out until the end of the buffer */
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l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
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memcpy(buffer, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
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/* then get the rest (if any) from the beginning of the buffer */
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memcpy(buffer + l, fifo->buffer, len - l);
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/*
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* Ensure that we remove the bytes from the kfifo -before-
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* we update the fifo->out index.
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*/
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smp_mb();
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fifo->out += len;
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return len;
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}
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EXPORT_SYMBOL(__kfifo_get);
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