目前kernel的kfifo根据版本有两种形式， 早期的函数形式和现在的宏定义形式
1. 早期的（linux-3.0.56/kernel/kfifo.c）
感兴趣读者可以自己看， 源码如下：
/* * A generic kernel FIFO implementation * * Copyright (C) 2009/2010 Stefani Seibold <stefani@seibold.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/log2.h> #include <linux/uaccess.h> #include <linux/kfifo.h> /* * internal helper to calculate the unused elements in a fifo */ static inline unsigned int kfifo_unused(struct __kfifo *fifo) { return (fifo->mask + 1) - (fifo->in - fifo->out); } int __kfifo_alloc(struct __kfifo *fifo, unsigned int size, size_t esize, gfp_t gfp_mask) { /* * round down to the next power of 2, since our 'let the indices * wrap' technique works only in this case. */ if (!is_power_of_2(size)) size = rounddown_pow_of_two(size); fifo->in = 0; fifo->out = 0; fifo->esize = esize; if (size < 2) { fifo->data = NULL; fifo->mask = 0; return -EINVAL; } fifo->data = kmalloc(size * esize, gfp_mask); if (!fifo->data) { fifo->mask = 0; return -ENOMEM; } fifo->mask = size - 1; return 0; } EXPORT_SYMBOL(__kfifo_alloc); void __kfifo_free(struct __kfifo *fifo) { kfree(fifo->data); fifo->in = 0; fifo->out = 0; fifo->esize = 0; fifo->data = NULL; fifo->mask = 0; } EXPORT_SYMBOL(__kfifo_free); int __kfifo_init(struct __kfifo *fifo, void *buffer, unsigned int size, size_t esize) { size /= esize; if (!is_power_of_2(size)) size = rounddown_pow_of_two(size); fifo->in = 0; fifo->out = 0; fifo->esize = esize; fifo->data = buffer; if (size < 2) { fifo->mask = 0; return -EINVAL; } fifo->mask = size - 1; return 0; } EXPORT_SYMBOL(__kfifo_init); static void kfifo_copy_in(struct __kfifo *fifo, const void *src, unsigned int len, unsigned int off) { unsigned int size = fifo->mask + 1; unsigned int esize = fifo->esize; unsigned int l; off &= fifo->mask; if (esize != 1) { off *= esize; size *= esize; len *= esize; } l = min(len, size - off); memcpy(fifo->data + off, src, l); memcpy(fifo->data, src + l, len - l); /* * make sure that the data in the fifo is up to date before * incrementing the fifo->in index counter */ smp_wmb(); } unsigned int __kfifo_in(struct __kfifo *fifo, const void *buf, unsigned int len) { unsigned int l; l = kfifo_unused(fifo); if (len > l) len = l; kfifo_copy_in(fifo, buf, len, fifo->in); fifo->in += len; return len; } EXPORT_SYMBOL(__kfifo_in); static void kfifo_copy_out(struct __kfifo *fifo, void *dst, unsigned int len, unsigned int off) { unsigned int size = fifo->mask + 1; unsigned int esize = fifo->esize; unsigned int l; off &= fifo->mask; if (esize != 1) { off *= esize; size *= esize; len *= esize; } l = min(len, size - off); memcpy(dst, fifo->data + off, l); memcpy(dst + l, fifo->data, len - l); /* * make sure that the data is copied before * incrementing the fifo->out index counter */ smp_wmb(); } unsigned int __kfifo_out_peek(struct __kfifo *fifo, void *buf, unsigned int len) { unsigned int l; l = fifo->in - fifo->out; if (len > l) len = l; kfifo_copy_out(fifo, buf, len, fifo->out); return len; } EXPORT_SYMBOL(__kfifo_out_peek); unsigned int __kfifo_out(struct __kfifo *fifo, void *buf, unsigned int len) { len = __kfifo_out_peek(fifo, buf, len); fifo->out += len; return len; } EXPORT_SYMBOL(__kfifo_out); static unsigned long kfifo_copy_from_user(struct __kfifo *fifo, const void __user *from, unsigned int len, unsigned int off, unsigned int *copied) { unsigned int size = fifo->mask + 1; unsigned int esize = fifo->esize; unsigned int l; unsigned long ret; off &= fifo->mask; if (esize != 1) { off *= esize; size *= esize; len *= esize; } l = min(len, size - off); ret = copy_from_user(fifo->data + off, from, l); if (unlikely(ret)) ret = DIV_ROUND_UP(ret + len - l, esize); else { ret = copy_from_user(fifo->data, from + l, len - l); if (unlikely(ret)) ret = DIV_ROUND_UP(ret, esize); } /* * make sure that the data in the fifo is up to date before * incrementing the fifo->in index counter */ smp_wmb(); *copied = len - ret; /* return the number of elements which are not copied */ return ret; } int __kfifo_from_user(struct __kfifo *fifo, const void __user *from, unsigned long len, unsigned int *copied) { unsigned int l; unsigned long ret; unsigned int esize = fifo->esize; int err; if (esize != 1) len /= esize; l = kfifo_unused(fifo); if (len > l) len = l; ret = kfifo_copy_from_user(fifo, from, len, fifo->in, copied); if (unlikely(ret)) { len -= ret; err = -EFAULT; } else err = 0; fifo->in += len; return err; } EXPORT_SYMBOL(__kfifo_from_user); static unsigned long kfifo_copy_to_user(struct __kfifo *fifo, void __user *to, unsigned int len, unsigned int off, unsigned int *copied) { unsigned int l; unsigned long ret; unsigned int size = fifo->mask + 1; unsigned int esize = fifo->esize; off &= fifo->mask; if (esize != 1) { off *= esize; size *= esize; len *= esize; } l = min(len, size - off); ret = copy_to_user(to, fifo->data + off, l); if (unlikely(ret)) ret = DIV_ROUND_UP(ret + len - l, esize); else { ret = copy_to_user(to + l, fifo->data, len - l); if (unlikely(ret)) ret = DIV_ROUND_UP(ret, esize); } /* * make sure that the data is copied before * incrementing the fifo->out index counter */ smp_wmb(); *copied = len - ret; /* return the number of elements which are not copied */ return ret; } int __kfifo_to_user(struct __kfifo *fifo, void __user *to, unsigned long len, unsigned int *copied) { unsigned int l; unsigned long ret; unsigned int esize = fifo->esize; int err; if (esize != 1) len /= esize; l = fifo->in - fifo->out; if (len > l) len = l; ret = kfifo_copy_to_user(fifo, to, len, fifo->out, copied); if (unlikely(ret)) { len -= ret; err = -EFAULT; } else err = 0; fifo->out += len; return err; } EXPORT_SYMBOL(__kfifo_to_user); static int setup_sgl_buf(struct scatterlist *sgl, void *buf, int nents, unsigned int len) { int n; unsigned int l; unsigned int off; struct page *page; if (!nents) return 0; if (!len) return 0; n = 0; page = virt_to_page(buf); off = offset_in_page(buf); l = 0; while (len >= l + PAGE_SIZE - off) { struct page *npage; l += PAGE_SIZE; buf += PAGE_SIZE; npage = virt_to_page(buf); if (page_to_phys(page) != page_to_phys(npage) - l) { sg_set_page(sgl, page, l - off, off); sgl = sg_next(sgl); if (++n == nents || sgl == NULL) return n; page = npage; len -= l - off; l = off = 0; } } sg_set_page(sgl, page, len, off); return n + 1; } static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len, unsigned int off) { unsigned int size = fifo->mask + 1; unsigned int esize = fifo->esize; unsigned int l; unsigned int n; off &= fifo->mask; if (esize != 1) { off *= esize; size *= esize; len *= esize; } l = min(len, size - off); n = setup_sgl_buf(sgl, fifo->data + off, nents, l); n += setup_sgl_buf(sgl + n, fifo->data, nents - n, len - l); return n; } unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len) { unsigned int l; l = kfifo_unused(fifo); if (len > l) len = l; return setup_sgl(fifo, sgl, nents, len, fifo->in); } EXPORT_SYMBOL(__kfifo_dma_in_prepare); unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len) { unsigned int l; l = fifo->in - fifo->out; if (len > l) len = l; return setup_sgl(fifo, sgl, nents, len, fifo->out); } EXPORT_SYMBOL(__kfifo_dma_out_prepare); unsigned int __kfifo_max_r(unsigned int len, size_t recsize) { unsigned int max = (1 << (recsize << 3)) - 1; if (len > max) return max; return len; } #define __KFIFO_PEEK(data, out, mask) ((data)[(out) & (mask)]) /* * __kfifo_peek_n internal helper function for determinate the length of * the next record in the fifo */ static unsigned int __kfifo_peek_n(struct __kfifo *fifo, size_t recsize) { unsigned int l; unsigned int mask = fifo->mask; unsigned char *data = fifo->data; l = __KFIFO_PEEK(data, fifo->out, mask); if (--recsize) l |= __KFIFO_PEEK(data, fifo->out + 1, mask) << 8; return l; } #define __KFIFO_POKE(data, in, mask, val) ( (data)[(in) & (mask)] = (unsigned char)(val) ) /* * __kfifo_poke_n internal helper function for storeing the length of * the record into the fifo */ static void __kfifo_poke_n(struct __kfifo *fifo, unsigned int n, size_t recsize) { unsigned int mask = fifo->mask; unsigned char *data = fifo->data; __KFIFO_POKE(data, fifo->in, mask, n); if (recsize > 1) __KFIFO_POKE(data, fifo->in + 1, mask, n >> 8); } unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize) { return __kfifo_peek_n(fifo, recsize); } EXPORT_SYMBOL(__kfifo_len_r); unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf, unsigned int len, size_t recsize) { if (len + recsize > kfifo_unused(fifo)) return 0; __kfifo_poke_n(fifo, len, recsize); kfifo_copy_in(fifo, buf, len, fifo->in + recsize); fifo->in += len + recsize; return len; } EXPORT_SYMBOL(__kfifo_in_r); static unsigned int kfifo_out_copy_r(struct __kfifo *fifo, void *buf, unsigned int len, size_t recsize, unsigned int *n) { *n = __kfifo_peek_n(fifo, recsize); if (len > *n) len = *n; kfifo_copy_out(fifo, buf, len, fifo->out + recsize); return len; } unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf, unsigned int len, size_t recsize) { unsigned int n; if (fifo->in == fifo->out) return 0; return kfifo_out_copy_r(fifo, buf, len, recsize, &n); } EXPORT_SYMBOL(__kfifo_out_peek_r); unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf, unsigned int len, size_t recsize) { unsigned int n; if (fifo->in == fifo->out) return 0; len = kfifo_out_copy_r(fifo, buf, len, recsize, &n); fifo->out += n + recsize; return len; } EXPORT_SYMBOL(__kfifo_out_r); void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize) { unsigned int n; n = __kfifo_peek_n(fifo, recsize); fifo->out += n + recsize; } EXPORT_SYMBOL(__kfifo_skip_r); int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from, unsigned long len, unsigned int *copied, size_t recsize) { unsigned long ret; len = __kfifo_max_r(len, recsize); if (len + recsize > kfifo_unused(fifo)) { *copied = 0; return 0; } __kfifo_poke_n(fifo, len, recsize); ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied); if (unlikely(ret)) { *copied = 0; return -EFAULT; } fifo->in += len + recsize; return 0; } EXPORT_SYMBOL(__kfifo_from_user_r); int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to, unsigned long len, unsigned int *copied, size_t recsize) { unsigned long ret; unsigned int n; if (fifo->in == fifo->out) { *copied = 0; return 0; } n = __kfifo_peek_n(fifo, recsize); if (len > n) len = n; ret = kfifo_copy_to_user(fifo, to, len, fifo->out + recsize, copied); if (unlikely(ret)) { *copied = 0; return -EFAULT; } fifo->out += n + recsize; return 0; } EXPORT_SYMBOL(__kfifo_to_user_r); unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len, size_t recsize) { if (!nents) BUG(); len = __kfifo_max_r(len, recsize); if (len + recsize > kfifo_unused(fifo)) return 0; return setup_sgl(fifo, sgl, nents, len, fifo->in + recsize); } EXPORT_SYMBOL(__kfifo_dma_in_prepare_r); void __kfifo_dma_in_finish_r(struct __kfifo *fifo, unsigned int len, size_t recsize) { len = __kfifo_max_r(len, recsize); __kfifo_poke_n(fifo, len, recsize); fifo->in += len + recsize; } EXPORT_SYMBOL(__kfifo_dma_in_finish_r); unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len, size_t recsize) { if (!nents) BUG(); len = __kfifo_max_r(len, recsize); if (len + recsize > fifo->in - fifo->out) return 0; return setup_sgl(fifo, sgl, nents, len, fifo->out + recsize); } EXPORT_SYMBOL(__kfifo_dma_out_prepare_r); void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize) { unsigned int len; len = __kfifo_peek_n(fifo, recsize); fifo->out += len + recsize; } EXPORT_SYMBOL(__kfifo_dma_out_finish_r);
我自己参考后修改的：
/* referrence linux kfifo.c */ #include <string.h> #include <stdlib.h> #include <errno.h> #include "fifo.h" #define min(x, y) ((x) < (y) ? (x) : (y)) #define smp_wmb() __asm__ __volatile__("": : :"memory") #define is_power_of_2(x) ((x) != 0 && (((x) & ((x) - 1)) == 0)) static unsigned int roundup_pow_of_two(unsigned int x) { int position = 0; int i; for (i = (x-1); i != 0; ++position) i >>= 1; return 1UL << position; } int kfifo_alloc(struct kfifo *fifo, unsigned int size) { fifo->in = 0; fifo->out = 0; if(size < 2) { fifo->data = NULL; fifo->mask = 0; return -EINVAL; } if(!is_power_of_2(size)) size = roundup_pow_of_two(size); fifo->data = malloc(size); if (!fifo->data) { fifo->mask = 0; return -ENOMEM; } fifo->mask = size - 1; return 0; } void kfifo_free(struct kfifo *fifo) { free(fifo->data); fifo->data = NULL; fifo->in = 0; fifo->out = 0; fifo->mask = 0; } static void kfifo_copy_in(struct kfifo *fifo, const void *src, unsigned int len, unsigned int off) { unsigned int size = fifo->mask + 1; unsigned int l; /* that is why request size is power of two, instead of off %= fifo->size */ off &= fifo->mask; l = min(len, size - off); memcpy(fifo->data + off, src, l); memcpy(fifo->data, src + l, len - l); /* make sure that the data in the fifo is up to date before * incrementing the fifo->in index counter */ smp_wmb(); } unsigned int kfifo_in(struct kfifo *fifo, const void *buf, unsigned int len) { unsigned int l; l = (fifo->mask + 1) - (fifo->in - fifo->out); if (len > l) len = l; kfifo_copy_in(fifo, buf, len, fifo->in); fifo->in += len; return len; } static void kfifo_copy_out(struct kfifo *fifo, void *dst, unsigned int len, unsigned int off) { unsigned int size = fifo->mask + 1; unsigned int l; off &= fifo->mask; l = min(len, size - off); memcpy(dst, fifo->data + off, l); memcpy(dst + l, fifo->data, len - l); /* make sure that the data is copied before * incrementing the fifo->out index counter */ smp_wmb(); } unsigned int kfifo_out(struct kfifo *fifo, void *buf, unsigned int len) { unsigned int l; l = fifo->in - fifo->out; if (len > l) len = l; kfifo_copy_out(fifo, buf, len, fifo->out); fifo->out += len; return len; }
上面in out函数故意不加锁， 由调用者根据情况自己加， 而不是一刀切在这里加影响性能， 头文件：
#ifndef __VEDIC_FIFO_H__ #define __VEDIC_FIFO_H__ struct kfifo { unsigned int in; unsigned int out; unsigned int mask; void *data; }; #define kfifo_size(fifo) ((fifo)->kfifo.mask + 1) int kfifo_alloc(struct kfifo *fifo, unsigned int size); void kfifo_free(struct kfifo *fifo); unsigned int kfifo_in(struct kfifo *fifo, const void *buf, unsigned int len); unsigned int kfifo_out(struct kfifo *fifo, void *buf, unsigned int len); #endif
测试代码和结果：
#include <stdio.h> #include "fifo.h" unsigned char buf[300]={0}; void main() { struct kfifo fifo; kfifo_alloc(&fifo, 255); printf("in counter %u ", kfifo_in(&fifo, buf, 20)); printf("out counter %u ", kfifo_out(&fifo, buf, 10)); } $ gcc -c fifo.c $ gcc -c main.c $ gcc fifo.o main.o -o main.bin $ ./main.bin in counter 20 out counter 10
关于in累加溢出的问题， 由于计算机存储是补码形式， 所以在一个ring buffer size下 （in - out） 还是正确的， 看测试case：
#include <stdio.h> int main() { unsigned char in=0, out=0, del; in = 250; out = 200; printf("1 in - out = %d ", in-out); in += 30; del = in - out; printf("2 in = %d, del = %d ", in, del); printf("3 in - out = %d ", in-out); /* enlarge */ in = 250; out = 200; in += 500; del = in - out; printf("4 in = %d, del = %d ", in, del); /* limit */ in = 250; out = 200; in += 255 - (in-out); // unsigned char max num = 255, not 256 del = in - out; printf("5 in = %d, del = %d ", in, del); } $ ./a.out 1 in - out = 50 2 in = 24, del = 80 3 in - out = -176 4 in = 238, del = 38 5 in = 199, del = 255
2. 现在的（只有头文件linux-3.10.65/include/linux/kfifo.h）
/* * A generic kernel FIFO implementation * * Copyright (C) 2009/2010 Stefani Seibold <stefani@seibold.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. * */ #ifndef _LINUX_KFIFO_H #define _LINUX_KFIFO_H /* * How to porting drivers to the new generic FIFO API: * * - Modify the declaration of the "struct kfifo *" object into a * in-place "struct kfifo" object * - Init the in-place object with kfifo_alloc() or kfifo_init() * Note: The address of the in-place "struct kfifo" object must be * passed as the first argument to this functions * - Replace the use of __kfifo_put into kfifo_in and __kfifo_get * into kfifo_out * - Replace the use of kfifo_put into kfifo_in_spinlocked and kfifo_get * into kfifo_out_spinlocked * Note: the spinlock pointer formerly passed to kfifo_init/kfifo_alloc * must be passed now to the kfifo_in_spinlocked and kfifo_out_spinlocked * as the last parameter * - The formerly __kfifo_* functions are renamed into kfifo_* */ /* * Note about locking : There is no locking required until only * one reader * and one writer is using the fifo and no kfifo_reset() will be * called * kfifo_reset_out() can be safely used, until it will be only called * in the reader thread. * For multiple writer and one reader there is only a need to lock the writer. * And vice versa for only one writer and multiple reader there is only a need * to lock the reader. */ #include <linux/kernel.h> #include <linux/spinlock.h> #include <linux/stddef.h> #include <linux/scatterlist.h> struct __kfifo { unsigned int in; unsigned int out; unsigned int mask; unsigned int esize; void *data; }; #define __STRUCT_KFIFO_COMMON(datatype, recsize, ptrtype) union { struct __kfifo kfifo; datatype *type; char (*rectype)[recsize]; ptrtype *ptr; const ptrtype *ptr_const; } #define __STRUCT_KFIFO(type, size, recsize, ptrtype) { __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); type buf[((size < 2) || (size & (size - 1))) ? -1 : size]; } #define STRUCT_KFIFO(type, size) struct __STRUCT_KFIFO(type, size, 0, type) #define __STRUCT_KFIFO_PTR(type, recsize, ptrtype) { __STRUCT_KFIFO_COMMON(type, recsize, ptrtype); type buf[0]; } #define STRUCT_KFIFO_PTR(type) struct __STRUCT_KFIFO_PTR(type, 0, type) /* * define compatibility "struct kfifo" for dynamic allocated fifos */ struct kfifo __STRUCT_KFIFO_PTR(unsigned char, 0, void); #define STRUCT_KFIFO_REC_1(size) struct __STRUCT_KFIFO(unsigned char, size, 1, void) #define STRUCT_KFIFO_REC_2(size) struct __STRUCT_KFIFO(unsigned char, size, 2, void) /* * define kfifo_rec types */ struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, 1, void); struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, 2, void); /* * helper macro to distinguish between real in place fifo where the fifo * array is a part of the structure and the fifo type where the array is * outside of the fifo structure. */ #define __is_kfifo_ptr(fifo) (sizeof(*fifo) == sizeof(struct __kfifo)) /** * DECLARE_KFIFO_PTR - macro to declare a fifo pointer object * @fifo: name of the declared fifo * @type: type of the fifo elements */ #define DECLARE_KFIFO_PTR(fifo, type) STRUCT_KFIFO_PTR(type) fifo /** * DECLARE_KFIFO - macro to declare a fifo object * @fifo: name of the declared fifo * @type: type of the fifo elements * @size: the number of elements in the fifo, this must be a power of 2 */ #define DECLARE_KFIFO(fifo, type, size) STRUCT_KFIFO(type, size) fifo /** * INIT_KFIFO - Initialize a fifo declared by DECLARE_KFIFO * @fifo: name of the declared fifo datatype */ #define INIT_KFIFO(fifo) (void)({ typeof(&(fifo)) __tmp = &(fifo); struct __kfifo *__kfifo = &__tmp->kfifo; __kfifo->in = 0; __kfifo->out = 0; __kfifo->mask = __is_kfifo_ptr(__tmp) ? 0 : ARRAY_SIZE(__tmp->buf) - 1; __kfifo->esize = sizeof(*__tmp->buf); __kfifo->data = __is_kfifo_ptr(__tmp) ? NULL : __tmp->buf; }) /** * DEFINE_KFIFO - macro to define and initialize a fifo * @fifo: name of the declared fifo datatype * @type: type of the fifo elements * @size: the number of elements in the fifo, this must be a power of 2 * * Note: the macro can be used for global and local fifo data type variables. */ #define DEFINE_KFIFO(fifo, type, size) DECLARE_KFIFO(fifo, type, size) = (typeof(fifo)) { { { .in = 0, .out = 0, .mask = __is_kfifo_ptr(&(fifo)) ? 0 : ARRAY_SIZE((fifo).buf) - 1, .esize = sizeof(*(fifo).buf), .data = __is_kfifo_ptr(&(fifo)) ? NULL : (fifo).buf, } } } static inline unsigned int __must_check __kfifo_uint_must_check_helper(unsigned int val) { return val; } static inline int __must_check __kfifo_int_must_check_helper(int val) { return val; } /** * kfifo_initialized - Check if the fifo is initialized * @fifo: address of the fifo to check * * Return %true if fifo is initialized, otherwise %false. * Assumes the fifo was 0 before. */ #define kfifo_initialized(fifo) ((fifo)->kfifo.mask) /** * kfifo_esize - returns the size of the element managed by the fifo * @fifo: address of the fifo to be used */ #define kfifo_esize(fifo) ((fifo)->kfifo.esize) /** * kfifo_recsize - returns the size of the record length field * @fifo: address of the fifo to be used */ #define kfifo_recsize(fifo) (sizeof(*(fifo)->rectype)) /** * kfifo_size - returns the size of the fifo in elements * @fifo: address of the fifo to be used */ #define kfifo_size(fifo) ((fifo)->kfifo.mask + 1) /** * kfifo_reset - removes the entire fifo content * @fifo: address of the fifo to be used * * Note: usage of kfifo_reset() is dangerous. It should be only called when the * fifo is exclusived locked or when it is secured that no other thread is * accessing the fifo. */ #define kfifo_reset(fifo) (void)({ typeof((fifo) + 1) __tmp = (fifo); __tmp->kfifo.in = __tmp->kfifo.out = 0; }) /** * kfifo_reset_out - skip fifo content * @fifo: address of the fifo to be used * * Note: The usage of kfifo_reset_out() is safe until it will be only called * from the reader thread and there is only one concurrent reader. Otherwise * it is dangerous and must be handled in the same way as kfifo_reset(). */ #define kfifo_reset_out(fifo) (void)({ typeof((fifo) + 1) __tmp = (fifo); __tmp->kfifo.out = __tmp->kfifo.in; }) /** * kfifo_len - returns the number of used elements in the fifo * @fifo: address of the fifo to be used */ #define kfifo_len(fifo) ({ typeof((fifo) + 1) __tmpl = (fifo); __tmpl->kfifo.in - __tmpl->kfifo.out; }) /** * kfifo_is_empty - returns true if the fifo is empty * @fifo: address of the fifo to be used */ #define kfifo_is_empty(fifo) ({ typeof((fifo) + 1) __tmpq = (fifo); __tmpq->kfifo.in == __tmpq->kfifo.out; }) /** * kfifo_is_full - returns true if the fifo is full * @fifo: address of the fifo to be used */ #define kfifo_is_full(fifo) ({ typeof((fifo) + 1) __tmpq = (fifo); kfifo_len(__tmpq) > __tmpq->kfifo.mask; }) /** * kfifo_avail - returns the number of unused elements in the fifo * @fifo: address of the fifo to be used */ #define kfifo_avail(fifo) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmpq = (fifo); const size_t __recsize = sizeof(*__tmpq->rectype); unsigned int __avail = kfifo_size(__tmpq) - kfifo_len(__tmpq); (__recsize) ? ((__avail <= __recsize) ? 0 : __kfifo_max_r(__avail - __recsize, __recsize)) : __avail; }) ) /** * kfifo_skip - skip output data * @fifo: address of the fifo to be used */ #define kfifo_skip(fifo) (void)({ typeof((fifo) + 1) __tmp = (fifo); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (__recsize) __kfifo_skip_r(__kfifo, __recsize); else __kfifo->out++; }) /** * kfifo_peek_len - gets the size of the next fifo record * @fifo: address of the fifo to be used * * This function returns the size of the next fifo record in number of bytes. */ #define kfifo_peek_len(fifo) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; (!__recsize) ? kfifo_len(__tmp) * sizeof(*__tmp->type) : __kfifo_len_r(__kfifo, __recsize); }) ) /** * kfifo_alloc - dynamically allocates a new fifo buffer * @fifo: pointer to the fifo * @size: the number of elements in the fifo, this must be a power of 2 * @gfp_mask: get_free_pages mask, passed to kmalloc() * * This macro dynamically allocates a new fifo buffer. * * The numer of elements will be rounded-up to a power of 2. * The fifo will be release with kfifo_free(). * Return 0 if no error, otherwise an error code. */ #define kfifo_alloc(fifo, size, gfp_mask) __kfifo_int_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); struct __kfifo *__kfifo = &__tmp->kfifo; __is_kfifo_ptr(__tmp) ? __kfifo_alloc(__kfifo, size, sizeof(*__tmp->type), gfp_mask) : -EINVAL; }) ) /** * kfifo_free - frees the fifo * @fifo: the fifo to be freed */ #define kfifo_free(fifo) ({ typeof((fifo) + 1) __tmp = (fifo); struct __kfifo *__kfifo = &__tmp->kfifo; if (__is_kfifo_ptr(__tmp)) __kfifo_free(__kfifo); }) /** * kfifo_init - initialize a fifo using a preallocated buffer * @fifo: the fifo to assign the buffer * @buffer: the preallocated buffer to be used * @size: the size of the internal buffer, this have to be a power of 2 * * This macro initialize a fifo using a preallocated buffer. * * The numer of elements will be rounded-up to a power of 2. * Return 0 if no error, otherwise an error code. */ #define kfifo_init(fifo, buffer, size) ({ typeof((fifo) + 1) __tmp = (fifo); struct __kfifo *__kfifo = &__tmp->kfifo; __is_kfifo_ptr(__tmp) ? __kfifo_init(__kfifo, buffer, size, sizeof(*__tmp->type)) : -EINVAL; }) /** * kfifo_put - put data into the fifo * @fifo: address of the fifo to be used * @val: the data to be added * * This macro copies the given value into the fifo. * It returns 0 if the fifo was full. Otherwise it returns the number * processed elements. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_put(fifo, val) ({ typeof((fifo) + 1) __tmp = (fifo); typeof((val) + 1) __val = (val); unsigned int __ret; const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) { typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); __dummy = (typeof(__val))NULL; } if (__recsize) __ret = __kfifo_in_r(__kfifo, __val, sizeof(*__val), __recsize); else { __ret = !kfifo_is_full(__tmp); if (__ret) { (__is_kfifo_ptr(__tmp) ? ((typeof(__tmp->type))__kfifo->data) : (__tmp->buf) )[__kfifo->in & __tmp->kfifo.mask] = *(typeof(__tmp->type))__val; smp_wmb(); __kfifo->in++; } } __ret; }) /** * kfifo_get - get data from the fifo * @fifo: address of the fifo to be used * @val: the var where to store the data to be added * * This macro reads the data from the fifo. * It returns 0 if the fifo was empty. Otherwise it returns the number * processed elements. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_get(fifo, val) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); typeof((val) + 1) __val = (val); unsigned int __ret; const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) __val = (typeof(__tmp->ptr))0; if (__recsize) __ret = __kfifo_out_r(__kfifo, __val, sizeof(*__val), __recsize); else { __ret = !kfifo_is_empty(__tmp); if (__ret) { *(typeof(__tmp->type))__val = (__is_kfifo_ptr(__tmp) ? ((typeof(__tmp->type))__kfifo->data) : (__tmp->buf) )[__kfifo->out & __tmp->kfifo.mask]; smp_wmb(); __kfifo->out++; } } __ret; }) ) /** * kfifo_peek - get data from the fifo without removing * @fifo: address of the fifo to be used * @val: the var where to store the data to be added * * This reads the data from the fifo without removing it from the fifo. * It returns 0 if the fifo was empty. Otherwise it returns the number * processed elements. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_peek(fifo, val) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); typeof((val) + 1) __val = (val); unsigned int __ret; const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) __val = (typeof(__tmp->ptr))NULL; if (__recsize) __ret = __kfifo_out_peek_r(__kfifo, __val, sizeof(*__val), __recsize); else { __ret = !kfifo_is_empty(__tmp); if (__ret) { *(typeof(__tmp->type))__val = (__is_kfifo_ptr(__tmp) ? ((typeof(__tmp->type))__kfifo->data) : (__tmp->buf) )[__kfifo->out & __tmp->kfifo.mask]; smp_wmb(); } } __ret; }) ) /** * kfifo_in - put data into the fifo * @fifo: address of the fifo to be used * @buf: the data to be added * @n: number of elements to be added * * This macro copies the given buffer into the fifo and returns the * number of copied elements. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_in(fifo, buf, n) ({ typeof((fifo) + 1) __tmp = (fifo); typeof((buf) + 1) __buf = (buf); unsigned long __n = (n); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) { typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); __dummy = (typeof(__buf))NULL; } (__recsize) ? __kfifo_in_r(__kfifo, __buf, __n, __recsize) : __kfifo_in(__kfifo, __buf, __n); }) /** * kfifo_in_spinlocked - put data into the fifo using a spinlock for locking * @fifo: address of the fifo to be used * @buf: the data to be added * @n: number of elements to be added * @lock: pointer to the spinlock to use for locking * * This macro copies the given values buffer into the fifo and returns the * number of copied elements. */ #define kfifo_in_spinlocked(fifo, buf, n, lock) ({ unsigned long __flags; unsigned int __ret; spin_lock_irqsave(lock, __flags); __ret = kfifo_in(fifo, buf, n); spin_unlock_irqrestore(lock, __flags); __ret; }) /* alias for kfifo_in_spinlocked, will be removed in a future release */ #define kfifo_in_locked(fifo, buf, n, lock) kfifo_in_spinlocked(fifo, buf, n, lock) /** * kfifo_out - get data from the fifo * @fifo: address of the fifo to be used * @buf: pointer to the storage buffer * @n: max. number of elements to get * * This macro get some data from the fifo and return the numbers of elements * copied. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_out(fifo, buf, n) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); typeof((buf) + 1) __buf = (buf); unsigned long __n = (n); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) { typeof(__tmp->ptr) __dummy = NULL; __buf = __dummy; } (__recsize) ? __kfifo_out_r(__kfifo, __buf, __n, __recsize) : __kfifo_out(__kfifo, __buf, __n); }) ) /** * kfifo_out_spinlocked - get data from the fifo using a spinlock for locking * @fifo: address of the fifo to be used * @buf: pointer to the storage buffer * @n: max. number of elements to get * @lock: pointer to the spinlock to use for locking * * This macro get the data from the fifo and return the numbers of elements * copied. */ #define kfifo_out_spinlocked(fifo, buf, n, lock) __kfifo_uint_must_check_helper( ({ unsigned long __flags; unsigned int __ret; spin_lock_irqsave(lock, __flags); __ret = kfifo_out(fifo, buf, n); spin_unlock_irqrestore(lock, __flags); __ret; }) ) /* alias for kfifo_out_spinlocked, will be removed in a future release */ #define kfifo_out_locked(fifo, buf, n, lock) kfifo_out_spinlocked(fifo, buf, n, lock) /** * kfifo_from_user - puts some data from user space into the fifo * @fifo: address of the fifo to be used * @from: pointer to the data to be added * @len: the length of the data to be added * @copied: pointer to output variable to store the number of copied bytes * * This macro copies at most @len bytes from the @from into the * fifo, depending of the available space and returns -EFAULT/0. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_from_user(fifo, from, len, copied) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); const void __user *__from = (from); unsigned int __len = (len); unsigned int *__copied = (copied); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; (__recsize) ? __kfifo_from_user_r(__kfifo, __from, __len, __copied, __recsize) : __kfifo_from_user(__kfifo, __from, __len, __copied); }) ) /** * kfifo_to_user - copies data from the fifo into user space * @fifo: address of the fifo to be used * @to: where the data must be copied * @len: the size of the destination buffer * @copied: pointer to output variable to store the number of copied bytes * * This macro copies at most @len bytes from the fifo into the * @to buffer and returns -EFAULT/0. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_to_user(fifo, to, len, copied) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); void __user *__to = (to); unsigned int __len = (len); unsigned int *__copied = (copied); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; (__recsize) ? __kfifo_to_user_r(__kfifo, __to, __len, __copied, __recsize) : __kfifo_to_user(__kfifo, __to, __len, __copied); }) ) /** * kfifo_dma_in_prepare - setup a scatterlist for DMA input * @fifo: address of the fifo to be used * @sgl: pointer to the scatterlist array * @nents: number of entries in the scatterlist array * @len: number of elements to transfer * * This macro fills a scatterlist for DMA input. * It returns the number entries in the scatterlist array. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macros. */ #define kfifo_dma_in_prepare(fifo, sgl, nents, len) ({ typeof((fifo) + 1) __tmp = (fifo); struct scatterlist *__sgl = (sgl); int __nents = (nents); unsigned int __len = (len); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; (__recsize) ? __kfifo_dma_in_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : __kfifo_dma_in_prepare(__kfifo, __sgl, __nents, __len); }) /** * kfifo_dma_in_finish - finish a DMA IN operation * @fifo: address of the fifo to be used * @len: number of bytes to received * * This macro finish a DMA IN operation. The in counter will be updated by * the len parameter. No error checking will be done. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macros. */ #define kfifo_dma_in_finish(fifo, len) (void)({ typeof((fifo) + 1) __tmp = (fifo); unsigned int __len = (len); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (__recsize) __kfifo_dma_in_finish_r(__kfifo, __len, __recsize); else __kfifo->in += __len / sizeof(*__tmp->type); }) /** * kfifo_dma_out_prepare - setup a scatterlist for DMA output * @fifo: address of the fifo to be used * @sgl: pointer to the scatterlist array * @nents: number of entries in the scatterlist array * @len: number of elements to transfer * * This macro fills a scatterlist for DMA output which at most @len bytes * to transfer. * It returns the number entries in the scatterlist array. * A zero means there is no space available and the scatterlist is not filled. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macros. */ #define kfifo_dma_out_prepare(fifo, sgl, nents, len) ({ typeof((fifo) + 1) __tmp = (fifo); struct scatterlist *__sgl = (sgl); int __nents = (nents); unsigned int __len = (len); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; (__recsize) ? __kfifo_dma_out_prepare_r(__kfifo, __sgl, __nents, __len, __recsize) : __kfifo_dma_out_prepare(__kfifo, __sgl, __nents, __len); }) /** * kfifo_dma_out_finish - finish a DMA OUT operation * @fifo: address of the fifo to be used * @len: number of bytes transferd * * This macro finish a DMA OUT operation. The out counter will be updated by * the len parameter. No error checking will be done. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macros. */ #define kfifo_dma_out_finish(fifo, len) (void)({ typeof((fifo) + 1) __tmp = (fifo); unsigned int __len = (len); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (__recsize) __kfifo_dma_out_finish_r(__kfifo, __recsize); else __kfifo->out += __len / sizeof(*__tmp->type); }) /** * kfifo_out_peek - gets some data from the fifo * @fifo: address of the fifo to be used * @buf: pointer to the storage buffer * @n: max. number of elements to get * * This macro get the data from the fifo and return the numbers of elements * copied. The data is not removed from the fifo. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these macro. */ #define kfifo_out_peek(fifo, buf, n) __kfifo_uint_must_check_helper( ({ typeof((fifo) + 1) __tmp = (fifo); typeof((buf) + 1) __buf = (buf); unsigned long __n = (n); const size_t __recsize = sizeof(*__tmp->rectype); struct __kfifo *__kfifo = &__tmp->kfifo; if (0) { typeof(__tmp->ptr) __dummy __attribute__ ((unused)) = NULL; __buf = __dummy; } (__recsize) ? __kfifo_out_peek_r(__kfifo, __buf, __n, __recsize) : __kfifo_out_peek(__kfifo, __buf, __n); }) ) extern int __kfifo_alloc(struct __kfifo *fifo, unsigned int size, size_t esize, gfp_t gfp_mask); extern void __kfifo_free(struct __kfifo *fifo); extern int __kfifo_init(struct __kfifo *fifo, void *buffer, unsigned int size, size_t esize); extern unsigned int __kfifo_in(struct __kfifo *fifo, const void *buf, unsigned int len); extern unsigned int __kfifo_out(struct __kfifo *fifo, void *buf, unsigned int len); extern int __kfifo_from_user(struct __kfifo *fifo, const void __user *from, unsigned long len, unsigned int *copied); extern int __kfifo_to_user(struct __kfifo *fifo, void __user *to, unsigned long len, unsigned int *copied); extern unsigned int __kfifo_dma_in_prepare(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len); extern unsigned int __kfifo_dma_out_prepare(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len); extern unsigned int __kfifo_out_peek(struct __kfifo *fifo, void *buf, unsigned int len); extern unsigned int __kfifo_in_r(struct __kfifo *fifo, const void *buf, unsigned int len, size_t recsize); extern unsigned int __kfifo_out_r(struct __kfifo *fifo, void *buf, unsigned int len, size_t recsize); extern int __kfifo_from_user_r(struct __kfifo *fifo, const void __user *from, unsigned long len, unsigned int *copied, size_t recsize); extern int __kfifo_to_user_r(struct __kfifo *fifo, void __user *to, unsigned long len, unsigned int *copied, size_t recsize); extern unsigned int __kfifo_dma_in_prepare_r(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len, size_t recsize); extern void __kfifo_dma_in_finish_r(struct __kfifo *fifo, unsigned int len, size_t recsize); extern unsigned int __kfifo_dma_out_prepare_r(struct __kfifo *fifo, struct scatterlist *sgl, int nents, unsigned int len, size_t recsize); extern void __kfifo_dma_out_finish_r(struct __kfifo *fifo, size_t recsize); extern unsigned int __kfifo_len_r(struct __kfifo *fifo, size_t recsize); extern void __kfifo_skip_r(struct __kfifo *fifo, size_t recsize); extern unsigned int __kfifo_out_peek_r(struct __kfifo *fifo, void *buf, unsigned int len, size_t recsize); extern unsigned int __kfifo_max_r(unsigned int len, size_t recsize); #endif
如何使用请参考kernel其他文件使用 ： DEFINE_KFIFO kfifo_put kfifo_get
最重要的是存储的数据类型不仅是之前的unsigned char， 还可以是struct！ 这才牛逼！