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 #ifdef __KERNEL__ 25 26 #include <linux/kernel.h> 27 #include <linux/spinlock.h> 28 29 struct kfifo { 30 unsigned char *buffer; /* the buffer holding the data */ 31 unsigned int size; /* the size of the allocated buffer */ 32 unsigned int in; /* data is added at offset (in % size) */ 33 unsigned int out; /* data is extracted from off. (out % size) */ 34 spinlock_t *lock; /* protects concurrent modifications */ 35 }; 36 37 extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size, 38 gfp_t gfp_mask, spinlock_t *lock); 39 extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask, 40 spinlock_t *lock); 41 extern void kfifo_free(struct kfifo *fifo); 42 extern unsigned int __kfifo_put(struct kfifo *fifo, 43 unsigned char *buffer, unsigned int len); 44 extern unsigned int __kfifo_get(struct kfifo *fifo, 45 unsigned char *buffer, unsigned int len); 46 47 /** 48 * __kfifo_reset - removes the entire FIFO contents, no locking version 49 * @fifo: the fifo to be emptied. 50 */ 51 static inline void __kfifo_reset(struct kfifo *fifo) 52 { 53 fifo->in = fifo->out = 0; 54 } 55 56 /** 57 * kfifo_reset - removes the entire FIFO contents 58 * @fifo: the fifo to be emptied. 59 */ 60 static inline void kfifo_reset(struct kfifo *fifo) 61 { 62 unsigned long flags; 63 64 spin_lock_irqsave(fifo->lock, flags); 65 66 __kfifo_reset(fifo); 67 68 spin_unlock_irqrestore(fifo->lock, flags); 69 } 70 71 /** 72 * kfifo_put - puts some data into the FIFO 73 * @fifo: the fifo to be used. 74 * @buffer: the data to be added. 75 * @len: the length of the data to be added. 76 * 77 * This function copies at most @len bytes from the @buffer into 78 * the FIFO depending on the free space, and returns the number of 79 * bytes copied. 80 */ 81 static inline unsigned int kfifo_put(struct kfifo *fifo, 82 unsigned char *buffer, unsigned int len) 83 { 84 unsigned long flags; 85 unsigned int ret; 86 87 spin_lock_irqsave(fifo->lock, flags); 88 89 ret = __kfifo_put(fifo, buffer, len); 90 91 spin_unlock_irqrestore(fifo->lock, flags); 92 93 return ret; 94 } 95 96 /** 97 * kfifo_get - gets some data from the FIFO 98 * @fifo: the fifo to be used. 99 * @buffer: where the data must be copied. 100 * @len: the size of the destination buffer. 101 * 102 * This function copies at most @len bytes from the FIFO into the 103 * @buffer and returns the number of copied bytes. 104 */ 105 static inline unsigned int kfifo_get(struct kfifo *fifo, 106 unsigned char *buffer, unsigned int len) 107 { 108 unsigned long flags; 109 unsigned int ret; 110 111 spin_lock_irqsave(fifo->lock, flags); 112 113 ret = __kfifo_get(fifo, buffer, len); 114 115 /* 116 * optimization: if the FIFO is empty, set the indices to 0 117 * so we don't wrap the next time 118 */ 119 if (fifo->in == fifo->out) 120 fifo->in = fifo->out = 0; 121 122 spin_unlock_irqrestore(fifo->lock, flags); 123 124 return ret; 125 } 126 127 /** 128 * __kfifo_len - returns the number of bytes available in the FIFO, no locking version 129 * @fifo: the fifo to be used. 130 */ 131 static inline unsigned int __kfifo_len(struct kfifo *fifo) 132 { 133 return fifo->in - fifo->out; 134 } 135 136 /** 137 * kfifo_len - returns the number of bytes available in the FIFO 138 * @fifo: the fifo to be used. 139 */ 140 static inline unsigned int kfifo_len(struct kfifo *fifo) 141 { 142 unsigned long flags; 143 unsigned int ret; 144 145 spin_lock_irqsave(fifo->lock, flags); 146 147 ret = __kfifo_len(fifo); 148 149 spin_unlock_irqrestore(fifo->lock, flags); 150 151 return ret; 152 } 153 154 #else 155 #warning "don't include kernel headers in userspace" 156 #endif /* __KERNEL__ */ 157 #endif 158