内核ring buffer -- kfifo
2024-10-19 08:58:24
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 + ) - (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 = ;
fifo->out = ;
fifo->esize = esize; if (size < ) {
fifo->data = NULL;
fifo->mask = ;
return -EINVAL;
} fifo->data = kmalloc(size * esize, gfp_mask); if (!fifo->data) {
fifo->mask = ;
return -ENOMEM;
}
fifo->mask = size - ; return ;
}
EXPORT_SYMBOL(__kfifo_alloc); void __kfifo_free(struct __kfifo *fifo)
{
kfree(fifo->data);
fifo->in = ;
fifo->out = ;
fifo->esize = ;
fifo->data = NULL;
fifo->mask = ;
}
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 = ;
fifo->out = ;
fifo->esize = esize;
fifo->data = buffer; if (size < ) {
fifo->mask = ;
return -EINVAL;
}
fifo->mask = size - ; return ;
}
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 + ;
unsigned int esize = fifo->esize;
unsigned int l; off &= fifo->mask;
if (esize != ) {
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 + ;
unsigned int esize = fifo->esize;
unsigned int l; off &= fifo->mask;
if (esize != ) {
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 + ;
unsigned int esize = fifo->esize;
unsigned int l;
unsigned long ret; off &= fifo->mask;
if (esize != ) {
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 != )
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 = ;
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 + ;
unsigned int esize = fifo->esize; off &= fifo->mask;
if (esize != ) {
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 != )
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 = ;
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 ; if (!len)
return ; n = ;
page = virt_to_page(buf);
off = offset_in_page(buf);
l = ; 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 = ;
}
}
sg_set_page(sgl, page, len, off);
return n + ;
} static unsigned int setup_sgl(struct __kfifo *fifo, struct scatterlist *sgl,
int nents, unsigned int len, unsigned int off)
{
unsigned int size = fifo->mask + ;
unsigned int esize = fifo->esize;
unsigned int l;
unsigned int n; off &= fifo->mask;
if (esize != ) {
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 = ( << (recsize << )) - ; 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 + , mask) << ; 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 > )
__KFIFO_POKE(data, fifo->in + , mask, n >> );
} 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 ; __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 ; 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 ; 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 = ;
return ;
} __kfifo_poke_n(fifo, len, recsize); ret = kfifo_copy_from_user(fifo, from, len, fifo->in + recsize, copied);
if (unlikely(ret)) {
*copied = ;
return -EFAULT;
}
fifo->in += len + recsize;
return ;
}
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 = ;
return ;
} 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 = ;
return -EFAULT;
}
fifo->out += n + recsize;
return ;
}
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 ; 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 ; 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);
linux-3.0.56/kernel/kfifo.c
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 = ;
int i; for (i = (x-); i != ; ++position)
i >>= ; return 1UL << position;
} int kfifo_alloc(struct kfifo *fifo, unsigned int size)
{
fifo->in = ;
fifo->out = ; if(size < ) {
fifo->data = NULL;
fifo->mask = ;
return -EINVAL;
} if(!is_power_of_2(size))
size = roundup_pow_of_two(size); fifo->data = malloc(size); if (!fifo->data) {
fifo->mask = ;
return -ENOMEM;
}
fifo->mask = size - ; return ;
} void kfifo_free(struct kfifo *fifo)
{
free(fifo->data);
fifo->data = NULL;
fifo->in = ;
fifo->out = ;
fifo->mask = ;
} static void kfifo_copy_in(struct kfifo *fifo, const void *src, unsigned int len, unsigned int off)
{
unsigned int size = fifo->mask + ;
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 + ) - (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 + ;
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[]={}; void main()
{
struct kfifo fifo; kfifo_alloc(&fifo, );
printf("in counter %u\n", kfifo_in(&fifo, buf, ));
printf("out counter %u\n", kfifo_out(&fifo, buf, ));
} $ gcc -c fifo.c
$ gcc -c main.c
$ gcc fifo.o main.o -o main.bin
$ ./main.bin
in counter
out counter
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=, out=, del; in = ;
out = ;
printf("1 in - out = %d\n", in-out); in += ;
del = in - out;
printf("2 in = %d, del = %d\n", in, del);
printf("3 in - out = %d\n", in-out); /* enlarge */
in = ;
out = ;
in += ;
del = in - out;
printf("4 in = %d, del = %d\n", in, del); /* limit */
in = ;
out = ;
in += - (in-out); // unsigned char max num = 255, not 256
del = in - out;
printf("5 in = %d, del = %d\n", in, del); } $ ./a.out
in - out =
in = , del =
in - out = -
in = , del =
in = , del =
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 < ) || (size & (size - ))) ? - : size]; \
} #define STRUCT_KFIFO(type, size) \
struct __STRUCT_KFIFO(type, size, , type) #define __STRUCT_KFIFO_PTR(type, recsize, ptrtype) \
{ \
__STRUCT_KFIFO_COMMON(type, recsize, ptrtype); \
type buf[]; \
} #define STRUCT_KFIFO_PTR(type) \
struct __STRUCT_KFIFO_PTR(type, , type) /*
* define compatibility "struct kfifo" for dynamic allocated fifos
*/
struct kfifo __STRUCT_KFIFO_PTR(unsigned char, , void); #define STRUCT_KFIFO_REC_1(size) \
struct __STRUCT_KFIFO(unsigned char, size, , void) #define STRUCT_KFIFO_REC_2(size) \
struct __STRUCT_KFIFO(unsigned char, size, , void) /*
* define kfifo_rec types
*/
struct kfifo_rec_ptr_1 __STRUCT_KFIFO_PTR(unsigned char, , void);
struct kfifo_rec_ptr_2 __STRUCT_KFIFO_PTR(unsigned char, , 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 = ; \
__kfifo->out = ; \
__kfifo->mask = __is_kfifo_ptr(__tmp) ? : ARRAY_SIZE(__tmp->buf) - ;\
__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 = , \
.out = , \
.mask = __is_kfifo_ptr(&(fifo)) ? \
: \
ARRAY_SIZE((fifo).buf) - , \
.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) + ) __tmp = (fifo); \
__tmp->kfifo.in = __tmp->kfifo.out = ; \
}) /**
* 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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __tmpq = (fifo); \
const size_t __recsize = sizeof(*__tmpq->rectype); \
unsigned int __avail = kfifo_size(__tmpq) - kfifo_len(__tmpq); \
(__recsize) ? ((__avail <= __recsize) ? : \
__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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __tmp = (fifo); \
typeof((val) + ) __val = (val); \
unsigned int __ret; \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () { \
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) + ) __tmp = (fifo); \
typeof((val) + ) __val = (val); \
unsigned int __ret; \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () \
__val = (typeof(__tmp->ptr)); \
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) + ) __tmp = (fifo); \
typeof((val) + ) __val = (val); \
unsigned int __ret; \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () \
__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) + ) __tmp = (fifo); \
typeof((buf) + ) __buf = (buf); \
unsigned long __n = (n); \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () { \
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) + ) __tmp = (fifo); \
typeof((buf) + ) __buf = (buf); \
unsigned long __n = (n); \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () { \
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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __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) + ) __tmp = (fifo); \
typeof((buf) + ) __buf = (buf); \
unsigned long __n = (n); \
const size_t __recsize = sizeof(*__tmp->rectype); \
struct __kfifo *__kfifo = &__tmp->kfifo; \
if () { \
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！
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