1 /* 2 * A simple kernel FIFO implementation. 3 * 4 * Copyright (C) 2004 Stelian Pop <stelian@popies.net> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 19 * 20 */ 21 #ifndef _LINUX_KFIFO_H 22 #define _LINUX_KFIFO_H 23 24 #include <linux/kernel.h> 25 #include <linux/spinlock.h> 26 27 struct kfifo { 28 unsigned char *buffer; /* the buffer holding the data */ 29 unsigned int size; /* the size of the allocated buffer */ 30 unsigned int in; /* data is added at offset (in % size) */ 31 unsigned int out; /* data is extracted from off. (out % size) */ 32 spinlock_t *lock; /* protects concurrent modifications */ 33 }; 34 35 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size, 36 gfp_t gfp_mask, spinlock_t *lock); 37 extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, 38 spinlock_t *lock); 39 extern void kfifo_free(struct kfifo *fifo); 40 extern unsigned int __kfifo_put(struct kfifo *fifo, 41 const unsigned char *buffer, unsigned int len); 42 extern unsigned int __kfifo_get(struct kfifo *fifo, 43 unsigned char *buffer, unsigned int len); 44 45 /** 46 * __kfifo_reset - removes the entire FIFO contents, no locking version 47 * @fifo: the fifo to be emptied. 48 */ 49 static inline void __kfifo_reset(struct kfifo *fifo) 50 { 51 fifo->in = fifo->out = 0; 52 } 53 54 /** 55 * kfifo_reset - removes the entire FIFO contents 56 * @fifo: the fifo to be emptied. 57 */ 58 static inline void kfifo_reset(struct kfifo *fifo) 59 { 60 unsigned long flags; 61 62 spin_lock_irqsave(fifo->lock, flags); 63 64 __kfifo_reset(fifo); 65 66 spin_unlock_irqrestore(fifo->lock, flags); 67 } 68 69 /** 70 * kfifo_put - puts some data into the FIFO 71 * @fifo: the fifo to be used. 72 * @buffer: the data to be added. 73 * @len: the length of the data to be added. 74 * 75 * This function copies at most @len bytes from the @buffer into 76 * the FIFO depending on the free space, and returns the number of 77 * bytes copied. 78 */ 79 static inline unsigned int kfifo_put(struct kfifo *fifo, 80 const unsigned char *buffer, unsigned int len) 81 { 82 unsigned long flags; 83 unsigned int ret; 84 85 spin_lock_irqsave(fifo->lock, flags); 86 87 ret = __kfifo_put(fifo, buffer, len); 88 89 spin_unlock_irqrestore(fifo->lock, flags); 90 91 return ret; 92 } 93 94 /** 95 * kfifo_get - gets some data from the FIFO 96 * @fifo: the fifo to be used. 97 * @buffer: where the data must be copied. 98 * @len: the size of the destination buffer. 99 * 100 * This function copies at most @len bytes from the FIFO into the 101 * @buffer and returns the number of copied bytes. 102 */ 103 static inline unsigned int kfifo_get(struct kfifo *fifo, 104 unsigned char *buffer, unsigned int len) 105 { 106 unsigned long flags; 107 unsigned int ret; 108 109 spin_lock_irqsave(fifo->lock, flags); 110 111 ret = __kfifo_get(fifo, buffer, len); 112 113 /* 114 * optimization: if the FIFO is empty, set the indices to 0 115 * so we don't wrap the next time 116 */ 117 if (fifo->in == fifo->out) 118 fifo->in = fifo->out = 0; 119 120 spin_unlock_irqrestore(fifo->lock, flags); 121 122 return ret; 123 } 124 125 /** 126 * __kfifo_len - returns the number of bytes available in the FIFO, no locking version 127 * @fifo: the fifo to be used. 128 */ 129 static inline unsigned int __kfifo_len(struct kfifo *fifo) 130 { 131 return fifo->in - fifo->out; 132 } 133 134 /** 135 * kfifo_len - returns the number of bytes available in the FIFO 136 * @fifo: the fifo to be used. 137 */ 138 static inline unsigned int kfifo_len(struct kfifo *fifo) 139 { 140 unsigned long flags; 141 unsigned int ret; 142 143 spin_lock_irqsave(fifo->lock, flags); 144 145 ret = __kfifo_len(fifo); 146 147 spin_unlock_irqrestore(fifo->lock, flags); 148 149 return ret; 150 } 151 152 #endif 153