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kfifo: add kfifo_skip, kfifo_from_user and kfifo_to_user 

Add kfifo_reset_out() for save lockless discard the fifo output
 Add kfifo_skip() to skip a number of output bytes
 Add kfifo_from_user() to copy user space data into the fifo
 Add kfifo_to_user() to copy fifo data to user space

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Stefani Seibold 2009-12-21 14:37:31 -08:00 committed by Linus Torvalds
parent 37bdfbbfaa
commit a121f24acc
2 changed files with 174 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
include/linux/kfifo.h
View File

@ -124,6 +124,16 @@ static inline void kfifo_reset(struct kfifo *fifo)
fifo->in = fifo->out = 0;
}
/**
* kfifo_reset_out - skip FIFO contents
* @fifo: the fifo to be emptied.
*/
static inline void kfifo_reset_out(struct kfifo *fifo)
{
smp_mb();
fifo->out = fifo->in;
}
/**
* kfifo_size - returns the size of the fifo in bytes
* @fifo: the fifo to be used.
@ -231,4 +241,41 @@ static inline __must_check unsigned int kfifo_out_locked(struct kfifo *fifo,
return ret;
}
extern void kfifo_skip(struct kfifo *fifo, unsigned int len);
extern __must_check unsigned int kfifo_from_user(struct kfifo *fifo,
const void __user *from, unsigned int n);
extern __must_check unsigned int kfifo_to_user(struct kfifo *fifo,
void __user *to, unsigned int n);
/**
* __kfifo_add_out internal helper function for updating the out offset
*/
static inline void __kfifo_add_out(struct kfifo *fifo,
unsigned int off)
{
smp_mb();
fifo->out += off;
}
/**
* __kfifo_add_in internal helper function for updating the in offset
*/
static inline void __kfifo_add_in(struct kfifo *fifo,
unsigned int off)
{
smp_wmb();
fifo->in += off;
}
/**
* __kfifo_off internal helper function for calculating the index of a
* given offeset
*/
static inline unsigned int __kfifo_off(struct kfifo *fifo, unsigned int off)
{
return off & (fifo->size - 1);
}
#endif

147
kernel/kfifo.c
View File

@ -26,6 +26,7 @@
#include <linux/err.h>
#include <linux/kfifo.h>
#include <linux/log2.h>
#include <linux/uaccess.h>
static void _kfifo_init(struct kfifo *fifo, unsigned char *buffer,
unsigned int size)
@ -99,6 +100,21 @@ void kfifo_free(struct kfifo *fifo)
}
EXPORT_SYMBOL(kfifo_free);
/**
* kfifo_skip - skip output data
* @fifo: the fifo to be used.
* @len: number of bytes to skip
*/
void kfifo_skip(struct kfifo *fifo, unsigned int len)
{
if (len < kfifo_len(fifo)) {
__kfifo_add_out(fifo, len);
return;
}
kfifo_reset_out(fifo);
}
EXPORT_SYMBOL(kfifo_skip);
/**
* kfifo_in - puts some data into the FIFO
* @fifo: the fifo to be used.
@ -115,6 +131,7 @@ EXPORT_SYMBOL(kfifo_free);
unsigned int kfifo_in(struct kfifo *fifo,
const unsigned char *from, unsigned int len)
{
unsigned int off;
unsigned int l;
len = min(len, fifo->size - fifo->in + fifo->out);
@ -126,21 +143,16 @@ unsigned int kfifo_in(struct kfifo *fifo,
smp_mb();
off = __kfifo_off(fifo, fifo->in);
/* first put the data starting from fifo->in to buffer end */
l = min(len, fifo->size - (fifo->in & (fifo->size - 1)));
memcpy(fifo->buffer + (fifo->in & (fifo->size - 1)), from, l);
l = min(len, fifo->size - off);
memcpy(fifo->buffer + off, from, l);
/* then put the rest (if any) at the beginning of the buffer */
memcpy(fifo->buffer, from + l, len - l);
/*
* Ensure that we add the bytes to the kfifo -before-
* we update the fifo->in index.
*/
smp_wmb();
fifo->in += len;
__kfifo_add_in(fifo, len);
return len;
}
@ -161,6 +173,7 @@ EXPORT_SYMBOL(kfifo_in);
unsigned int kfifo_out(struct kfifo *fifo,
unsigned char *to, unsigned int len)
{
unsigned int off;
unsigned int l;
len = min(len, fifo->in - fifo->out);
@ -172,22 +185,116 @@ unsigned int kfifo_out(struct kfifo *fifo,
smp_rmb();
off = __kfifo_off(fifo, fifo->out);
/* first get the data from fifo->out until the end of the buffer */
l = min(len, fifo->size - (fifo->out & (fifo->size - 1)));
memcpy(to, fifo->buffer + (fifo->out & (fifo->size - 1)), l);
l = min(len, fifo->size - off);
memcpy(to, fifo->buffer + off, l);
/* then get the rest (if any) from the beginning of the buffer */
memcpy(to + l, fifo->buffer, len - l);
/*
* Ensure that we remove the bytes from the kfifo -before-
* we update the fifo->out index.
*/
smp_mb();
fifo->out += len;
__kfifo_add_out(fifo, len);
return len;
}
EXPORT_SYMBOL(kfifo_out);
/**
* kfifo_from_user - puts some data from user space into the FIFO
* @fifo: the fifo to be used.
* @from: pointer to the data to be added.
* @len: the length of the data to be added.
*
* This function copies at most @len bytes from the @from into the
* FIFO depending and returns the number of copied bytes.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int kfifo_from_user(struct kfifo *fifo,
const void __user *from, unsigned int len)
{
unsigned int off;
unsigned int l;
int ret;
len = min(len, fifo->size - fifo->in + fifo->out);
/*
* Ensure that we sample the fifo->out index -before- we
* start putting bytes into the kfifo.
*/
smp_mb();
off = __kfifo_off(fifo, fifo->in);
/* first put the data starting from fifo->in to buffer end */
l = min(len, fifo->size - off);
ret = copy_from_user(fifo->buffer + off, from, l);
if (unlikely(ret))
return l - ret;
/* then put the rest (if any) at the beginning of the buffer */
ret = copy_from_user(fifo->buffer, from + l, len - l);
if (unlikely(ret))
return len - ret;
__kfifo_add_in(fifo, len);
return len;
}
EXPORT_SYMBOL(kfifo_from_user);
/**
* kfifo_to_user - gets data from the FIFO and write it to user space
* @fifo: the fifo to be used.
* @to: where the data must be copied.
* @len: the size of the destination buffer.
*
* This function copies at most @len bytes from the FIFO into the
* @to buffer and returns the number of copied bytes.
*
* Note that with only one concurrent reader and one concurrent
* writer, you don't need extra locking to use these functions.
*/
unsigned int kfifo_to_user(struct kfifo *fifo,
void __user *to, unsigned int len)
{
unsigned int off;
unsigned int l;
int ret;
len = min(len, fifo->in - fifo->out);
/*
* Ensure that we sample the fifo->in index -before- we
* start removing bytes from the kfifo.
*/
smp_rmb();
off = __kfifo_off(fifo, fifo->out);
/* first get the data from fifo->out until the end of the buffer */
l = min(len, fifo->size - off);
ret = copy_to_user(to, fifo->buffer + off, l);
if (unlikely(ret))
return l - ret;
/* then get the rest (if any) from the beginning of the buffer */
ret = copy_to_user(to + l, fifo->buffer, len - l);
if (unlikely(ret))
return len - ret;
__kfifo_add_out(fifo, len);
return len;
}
EXPORT_SYMBOL(kfifo_to_user);