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Add generic support for read-ahead buffering and write buffering in block drivers

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@2227 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2009-11-05 18:15:06 +00:00
parent c0675a0711
commit 6b2827a112
3 changed files with 824 additions and 1 deletions
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2
drivers/Makefile
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@ -90,7 +90,7 @@ CSRCS =
ifneq ($(CONFIG_NFILE_DESCRIPTORS),0) ifneq ($(CONFIG_NFILE_DESCRIPTORS),0)
CSRCS += dev_null.c dev_zero.c loop.c can.c CSRCS += dev_null.c dev_zero.c loop.c can.c
ifneq ($(CONFIG_DISABLE_MOUNTPOINT),y) ifneq ($(CONFIG_DISABLE_MOUNTPOINT),y)
CSRCS += ramdisk.c CSRCS += ramdisk.c rwbuffer.c
endif endif
endif endif
CSRCS += $(SERIAL_CSRCS) $(NET_CSRCS) $(PIPE_CSRCS) $(USBDEV_CSRCS) \ CSRCS += $(SERIAL_CSRCS) $(NET_CSRCS) $(PIPE_CSRCS) $(USBDEV_CSRCS) \

643
drivers/rwbuffer.c Normal file
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@ -0,0 +1,643 @@
/****************************************************************************
* drivers/rwbuffer.c
*
* Copyright (C) 2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <semaphore.h>
#include <errno.h>
#include <wdog.h>
#include <debug.h>
#include <nuttx/rwbuffer.h>
#if defined(CONFIG_FS_WRITEBUFFER) || defined(CONFIG_FS_READAHEAD)
/****************************************************************************
* Preprocessor Definitions
****************************************************************************/
/* Configuration ************************************************************/
#ifndef CONFIG_FS_WRDELAY
# define CONFIG_FS_WRDELAY 350
#endif
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Public Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: rwb_semtake
****************************************************************************/
static void rwb_semtake(sem_t *sem)
{
/* Take the semaphore (perhaps waiting) */
while (sem_wait(sem) != 0)
{
/* The only case that an error should occr here is if
* the wait was awakened by a signal.
*/
ASSERT(errno == EINTR);
}
}
/****************************************************************************
* Name: rwb_semgive
****************************************************************************/
#define rwb_semgive(s) sem_post(s)
/****************************************************************************
* Name: rwb_overlap
****************************************************************************/
static inline boolean
rwb_overlap(off_t bufferstart1, size_t buffersize1,
off_t bufferstart2, size_t buffersize2)
{
off_t bufferend1 = bufferstart1 + buffersize1;
off_t bufferend2 = bufferstart2 + buffersize2;
/* If the buffer 1 is wholly outside of buffer 2, return false */
if ((bufferend1 < bufferstart2) || /* Wholly "below" */
(bufferstart1 > bufferend2)) /* Wholly "above" */
{
return FALSE;
}
else
{
return TRUE;
}
}
/****************************************************************************
* Name: rwb_resetwrbuffer
****************************************************************************/
#ifdef CONFIG_FS_WRITEBUFFER
static inline void rwb_resetwrbuffer(struct rwbuffer_s *rwb)
{
/* We assume that the caller holds the wrsem */
rwb->wrnbytes = 0;
rwb->wrblockstart = (off_t)-1;
rwb->wrexpectedblock = (off_t)-1;
}
#endif
/****************************************************************************
* Name: rwb_wrflush
****************************************************************************/
#ifdef CONFIG_FS_WRITEBUFFER
static void rwb_wrflush(struct rwbuffer_s *rwb)
{
int ret;
fvdbg("Timeout!");
rwb_semtake(&rwb->wrsem);
if (rwb->wrnbytes)
{
fvdbg("Flushing: blockstart=0x%08lx nbytes=%d from buffer=%p",
(long)rwb->wrblockstart, (long)rwb->wrnbytes, (long)rwb->wrbuffer);
/* Flush cache */
ret = rwb->wrflush(rwb->dev, rwb->wrbuffer, rwb->wrblockstart, rwb->wrnbytes);
if (ret < 0)
{
fdbg("ERROR: Error flushing write buffer: %d\n", -ret);
}
rwb_resetwrbuffer(rwb);
}
rwb_semgive(&rwb->wrsem);
}
#endif
/****************************************************************************
* Name: rwb_wrtimeout
****************************************************************************/
static void rwb_wrtimeout(int argc, uint32 irwb)
{
/* The following assumes that the size of a pointer is 4-bytes or less */
FAR struct rwbuffer_s *rwb = (struct rwbuffer_s *)irwb;
/* If a timeout elpases with with write buffer activity, this watchdog
* handler function will be evoked. This function will schedule to flush
* the write buffer. NOTE: This function runs in the context of the timer
* interrupt handler!
*/
DEBUGASSERT(argc == 1);
#warning "REVISIT: Missing logic"
}
/****************************************************************************
* Name: rwb_wrstarttimer
****************************************************************************/
static void rwb_wrstarttimer(FAR struct rwbuffer_s *rwb)
{
/* CONFIG_FS_WRDELAY provides the delay period in milliseconds. CLK_TCK
* provides the clock tick of the system (frequency in Hz).
*/
int ticks = (CONFIG_FS_WRDELAY + CLK_TCK/2) / CLK_TCK;
(void)wd_start(rwb->wdog, ticks, (wdentry_t)rwb_wrtimeout, 1, (uint32)rwb);
}
/****************************************************************************
* Name: rwb_wrcanceltimer
****************************************************************************/
static inline void rwb_wrcanceltimer(struct rwbuffer_s *rwb)
{
wd_cancel(rwb->wdog);
}
/****************************************************************************
* Name: rwb_writebuffer
****************************************************************************/
#ifdef CONFIG_FS_WRITEBUFFER
static ssize_t rwb_writebuffer(FAR struct rwbuffer_s *rwb,
off_t startblock, uint32 nbytes,
FAR const ubyte *wrbuffer)
{
int ret;
/* Write writebuffer Logic */
rwb_wrcanceltimer(rwb);
/* First: Should we flush out our cache? */
if (((startblock != rwb->wrexpectedblock) && (rwb->wrnbytes)) ||
((rwb->wrnbytes + nbytes) > rwb->wrallocsize))
{
fvdbg("writebuffer miss, expected: 0x%08x, given: 0x%08x",
rwb->wrexpectedblock, startblock);
/* Flush cache */
ret = rwb->wrflush(rwb, rwb->wrbuffer, rwb->wrblockstart, rwb->wrnbytes);
if (ret < 0)
{
fdbg("ERROR: Error writing multiple from cache: %d\n", -ret);
return ret;
}
rwb_resetwrbuffer(rwb);
}
/* writebuffer is clear? Then initialize it */
if (!rwb->wrnbytes)
{
fvdbg("Fresh cache starting at block: 0x%08x",startblock);
rwb->wrblockstart = startblock;
}
/* Add data to cache */
fvdbg("writebuffer: copying from 0x%p to 0x%p",
wrbuffer, &rwb->wrbuffer[rwb->wrnbytes]);
memcpy(&rwb->wrbuffer[rwb->wrnbytes], wrbuffer, nbytes);
rwb->wrnbytes += nbytes;
rwb->wrexpectedblock = rwb->wrblockstart + rwb->wrnbytes;
rwb_wrstarttimer(rwb);
return nbytes;
}
#endif
/****************************************************************************
* Name:
****************************************************************************/
#ifdef CONFIG_FS_READAHEAD
static inline void rwb_resetrhbuffer(struct rwbuffer_s *rwb)
{
/* We assume that the caller holds the readAheadBufferSemphore */
rwb->rhnbytes = 0;
rwb->rhblockstart = (off_t)-1;
}
#endif
/****************************************************************************
* Name:
****************************************************************************/
#ifdef CONFIG_FS_READAHEAD
static inline void
rwb_bufferread(struct rwbuffer_s *rwb, off_t startblock,
size_t nblocks, ubyte **rdbuffer)
{
/* We assume that (1) the caller holds the readAheadBufferSemphore, and (2)
* that the caller already knows that all of the blocks are in the
* read-ahead buffer.
*/
/* Convert the units from blocks to bytes */
uint32 dwStartBlockOffset = startblock - rwb->rhblockstart;
uint32 dwStartByteOffset = rwb->blocksize * dwStartBlockOffset;
uint32 dwByteCount = rwb->blocksize * nblocks;
/* Get the byte address in the read-ahead buffer */
ubyte *pchBuffer = rwb->rhbuffer + dwStartByteOffset;
/* Copy the data from the read-ahead buffer into the IO buffer */
memcpy(*rdbuffer, pchBuffer, dwByteCount);
/* Update the caller's copy for the next address */
*rdbuffer += dwByteCount;
}
#endif
/****************************************************************************
* Name:
****************************************************************************/
#ifdef CONFIG_FS_READAHEAD
static int rwb_rhreload(struct rwbuffer_s *rwb, off_t startblock)
{
/* Get the maximum number of blocks that will fit in the read-ahead buffer */
size_t maxblocks = rwb->rhallocsize / rwb->blocksize;
off_t endblock = startblock + maxblocks;
size_t nblocks;
int ret;
/* Reset the read buffer */
rwb_resetrhbuffer(rwb);
/* Make sure that we don't read past the end of the device */
if (endblock > rwb->nblocks)
{
endblock = rwb->nblocks;
}
nblocks = endblock - startblock;
/* Now perform the read */
ret = rwb->rhreload(rwb->dev, rwb->rhbuffer, startblock, nblocks);
if (ret == 0)
{
/* Update information about what is in the read-ahead buffer */
rwb->rhnbytes = nblocks;
rwb->rhblockstart = startblock;
}
return ret;
}
#endif
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: rwb_initialize
****************************************************************************/
int rwb_initialize(FAR struct rwbuffer_s *rwb)
{
/* Sanity checking */
DEBUGASSERT(rwb != NULL);
DEBUGASSERT(rwb->blocksize > 0);
DEBUGASSERT(rwb->nblocks > 0);
DEBUGASSERT(rwb->dev != NULL);
/* Setup so that rwb_uninitialize can handle a failure */
#ifdef CONFIG_FS_WRITEBUFFER
DEBUGASSERT(rwb->wrblocks > 0);
DEBUGASSERT(rwb->wrflush!= NULL);
rwb->wrbuffer = NULL;
#endif
#ifdef CONFIG_FS_READAHEAD
DEBUGASSERT(rwb->rhnblocks > 0);
DEBUGASSERT(rwb->rhreload != NULL);
rwb->rhbuffer = NULL;
#endif
#ifdef CONFIG_FS_WRITEBUFFER
fvdbg("Initialize the write buffer");
/* Initialize the write buffer access semaphore */
sem_init(&rwb->wrsem, 0, 1);
/* Create a timer that will be used to flush buffered write data
* after a delay with no activity.
*/
rwb->wdog = wd_create();
/* Initialize write buffer parameters */
rwb_resetwrbuffer(rwb);
/* Allocate the write buffer */
rwb->wrallocsize = rwb->wrblocks * rwb->blocksize;
rwb->wrbuffer = malloc(rwb->wrallocsize);
if (!rwb->wrbuffer)
{
fdbg("Write buffer malloc(%ld) failed\n", (long)rwb->wrallocsize);
return -ENOMEM;
}
fvdbg("Write buffer size: %d bytes\n", rwb->wrallocsize);
#endif /* CONFIG_FS_WRITEBUFFER */
#ifdef CONFIG_FS_READAHEAD
fvdbg("Initialize the read-ahead buffer");
/* Initialize the read-ahead buffer access semaphore */
sem_init(&rwb->rhsem, 0, 1);
/* Initialize read-ahead buffer parameters */
rwb_resetrhbuffer(rwb);
/* Allocate the read-ahead buffer */
rwb->rhallocsize = rwb->rhblocks * rwb->blocksize;
rwb->rhbuffer = malloc(rwb->rhallocsize);
if (!rwb->rhbuffer)
{
fdbg("Read-ahead buffer malloc(%ld) failed\n", (long)rwb->rhallocsize);
return -ENOMEM;
}
fvdbg("Read-ahead buffer size: %d bytes\n", rwb->rhallocsize);
#endif /* CONFIG_FS_READAHEAD */
return 0;
}
/****************************************************************************
* Name: rwb_uninitialize
****************************************************************************/
void rwb_uninitialize(FAR struct rwbuffer_s *rwb)
{
#ifdef CONFIG_FS_WRITEBUFFER
sem_destroy(&rwb->wrsem);
wd_delete(rwb->wdog);
if (rwb->wrbuffer)
{
free(rwb->wrbuffer);
}
#endif
#ifdef CONFIG_FS_READAHEAD
sem_destroy(&rwb->rhsem);
if (rwb->rhbuffer)
{
free(rwb->rhbuffer);
}
#endif
}
/****************************************************************************
* Name:
****************************************************************************/
int rwb_read(FAR struct rwbuffer_s *rwb, off_t startblock, uint32 blockcount,
FAR ubyte *rdbuffer)
{
fvdbg("startblock=%ld blockcount=%ld rdbuffer=%p",
(long)startblock, (long)blockcount, rdbuffer);
#ifdef CONFIG_FS_WRITEBUFFER
/* If the new read data overlaps any part of the write buffer, then
* flush the write data onto the physical media before reading. We
* could attempt some more exotic handling -- but this simple logic
* is well-suited for simple streaming applications.
*/
/* If the write buffer overlaps the block(s) requested, then flush the
* write buffer.
*/
rwb_semtake(&rwb->wrsem);
if (rwb_overlap(rwb->wrblockstart, rwb->wrnbytes, startblock, blockcount))
{
rwb_wrflush(rwb);
}
rwb_semgive(&rwb->wrsem);
#endif
#ifdef CONFIG_FS_READAHEAD
/* Loop until we have read all of the requested blocks */
rwb_semtake(&rwb->rhsem);
while (blockcount > 0)
{
/* Is there anything in the read-ahead buffer? */
if (rwb->rhnbytes > 0)
{
off_t startblock = startblock;
size_t nblocks = 0;
off_t bufferend;
/* Loop for each block we find in the read-head buffer. Count the
* number of buffers that we can read from read-ahead buffer.
*/
bufferend = rwb->rhblockstart + rwb->rhnbytes;
while ((startblock >= rwb->rhblockstart) &&
(startblock < bufferend) &&
(blockcount > 0))
{
/* This is one more that we will read from the read ahead buffer */
nblocks++;
/* And one less that we will read from the media */
startblock++;
blockcount--;
}
/* Then read the data from the read-ahead buffer */
rwb_bufferread(rwb, startblock,
nblocks, &rdbuffer);
}
/* If we did not get all of the data from the buffer, then we have to refill
* the buffer and try again.
*/
if (blockcount > 0)
{
int ret = rwb_rhreload(rwb, startblock);
if (ret < 0)
{
fdbg("ERROR: Failed to fill the read-ahead buffer: %d", -ret);
return ret;
}
}
}
rwb_semgive(&rwb->rhsem);
return 0;
#else
return rwb->rhreload(rwb->dev, startblock, blockcount, rdbuffer);
#endif
}
/****************************************************************************
* Name: rwb_write
****************************************************************************/
int rwb_write(FAR struct rwbuffer_s *rwb, off_t startblock,
size_t blockcount, FAR const ubyte *wrbuffer)
{
int ret;
#ifdef CONFIG_FS_READAHEAD
/* If the new write data overlaps any part of the read buffer, then
* flush the data from the read buffer. We could attempt some more
* exotic handling -- but this simple logic is well-suited for simple
* streaming applications.
*/
rwb_semtake(&rwb->rhsem);
if (rwb_overlap(rwb->rhblockstart,
rwb->rhnbytes,
startblock, blockcount))
{
rwb_resetrhbuffer(rwb);
}
rwb_give(&rwb->rhsem);
#endif
#ifdef CONFIG_FS_WRITEBUFFER
fvdbg("startblock=%d wrbuffer=%p", startblock, wrbuffer);
/* Use the block cache unless the buffer size is bigger than block cache */
if (blockcount > rwb->wrallocsize)
{
/* First flush the cache */
rwb_semtake(&rwb->wrsem);
rwb_wrflush(rwb);
rwb_semgive(&rwb->wrsem);
/* Then transfer the data directly to the media */
ret = rwb->wrflush(rwb->dev, startblock, blockcount, wrbuffer);
}
else
{
/* Buffer the data in the write buffer */
ret = rwb_writebuffer(rwb, startblock, blockcount, wrbuffer);
}
return ret;
#else
return rwb->wrflush(rwb->dev, startblock, blockcount, wrbuffer);
#endif
}
/****************************************************************************
* Name: rwb_mediaremoved
****************************************************************************/
/* The following function is called when media is removed */
int rwb_mediaremoved(FAR struct rwbuffer_s *rwb)
{
#ifdef CONFIG_FS_WRITEBUFFER
rwb_semtake(&rwb->wrsem);
rwb_resetwrbuffer(rwb);
rwb_semgive(&rwb->wrsem);
#endif
#ifdef CONFIG_FS_READAHEAD
rwb_semtake(&rwb->rhsem);
rwb_resetrhbuffer(rwb);
rwb_semgive(&rwb->rhsem);
#endif
return 0;
}
#endif /* CONFIG_FS_WRITEBUFFER || CONFIG_FS_READAHEAD */

180
include/nuttx/rwbuffer.h Normal file
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@ -0,0 +1,180 @@
/****************************************************************************
* inlcude/nuttx/rwbuffer.h
*
* Copyright (C) 2009 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#ifndef __INCLUDE_NUTTX_RWBUFFER_H
#define __INCLUDE_NUTTX_RWBUFFER_H
/**********************************************************************
* Included Files
**********************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <semaphore.h>
#include <wdog.h>
#if defined(CONFIG_FS_WRITEBUFFER) || defined(CONFIG_FS_READAHEAD)
/**********************************************************************
* Definitions
**********************************************************************/
/**********************************************************************
* Public Types
**********************************************************************/
/* Data transfer callouts. These must be provided by the block driver
* logic in order to flush the write buffer when appropriate or to
* reload the read-ahead buffer, when appropriate.
*/
typedef ssize_t (*rwbreload_t)(FAR void *dev, FAR ubyte *buffer,
off_t start_sector, size_t nsectors);
typedef ssize_t (*rwbflush_t)(FAR void *dev, FAR const ubyte *buffer,
off_t start_sector, size_t nsectors);
/* This structure holds the state of the buffers. In typical usage,
* an instance of this structure is declared within each block driver
* status structure like:
*
* struct foo_dev_s
* {
* ...
* struct rwbuffer_s rwbuffer;
* ...
* };
*
* Note that this supports buffering for multiple block devices or for
* multiple instances of same block device, because each rwbuffer instance
* supports independent buffering.
*
* A reference to the struct rwbuffer_s instance is then passed to each
* interface like:
*
* struct foo_dev_s *priv;
* ...
* ... [Setup blocksize, nblocks, dev, wrblocks, wrflush, rhblocks, rhreload] ...
* ret = rwb_initialize(&priv->rwbuffer);
*/
struct rwbuffer_s
{
/********************************************************************/
/* These values must be provided by the user prior to calling rwb_initialize */
/* Supported geometry */
uint16 blocksize; /* The size of one block */
size_t nblocks; /* The total number blocks supported */
void *dev; /* Device state passed to callout functions */
#ifdef CONFIG_FS_WRITEBUFFER
uint16 wrblocks; /* The number of blocks to buffer in memory */
rwbflush_t wrflush; /* Callout to flush the write buffer */
#endif
#ifdef CONFIG_FS_READAHEAD
uint16 rhblocks; /* The number of blocks to buffer in memory */
rwbreload_t rhreload; /* Callout to reload the read-ahead buffer */
#endif
/********************************************************************/
/* The user should never modify any of the remaing fields */
/* This is the state of the write buffer */
#ifdef CONFIG_FS_WRITEBUFFER
sem_t wrsem; /* Enforces exclusive access to the write buffer */
WDOG_ID wdog; /* Watchdog fires after delay with no activity */
ubyte *wrbuffer; /* Allocated write buffer */
size_t wrnbytes; /* Bytes in write buffer */
off_t wrblockstart; /* First block in write buffer */
off_t wrexpectedblock; /* Next block expected */
size_t wrallocsize; /* Size of allocated write buffer */
#endif
/* This is the state of the read-ahead buffer */
#ifdef CONFIG_FS_READAHEAD
sem_t rhsem; /* Enforces exclusive access to the write buffer */
ubyte *rhbuffer; /* Allocated read-ahead buffer */
size_t rhnbytes; /* Blocks in read-ahead buffer */
off_t rhblockstart; /* First block in read-ahead buffer */
size_t rhallocsize; /* Size of allocated read-ahead buffer */
#endif
};
/**********************************************************************
* Global Variables
**********************************************************************/
#undef EXTERN
#if defined(__cplusplus)
#define EXTERN EXTERN "C"
EXTERN "C" {
#else
#define EXTERN extern
#endif
/**********************************************************************
* Global Function Prototypes
**********************************************************************/
/* Buffer initialization */
EXTERN int rwb_initialize(FAR struct rwbuffer_s *rwb);
EXTERN void rwb_uninitialize(FAR struct rwbuffer_s *rwb);
/* Buffer transfers */
EXTERN ssize_t rwb_read(FAR struct rwbuffer_s *rwb, off_t startblock,
size_t blockcount, FAR ubyte *rdbuffer);
EXTERN ssize_t rwb_write(FAR struct rwbuffer_s *rwb,
off_t startblock, size_t blockcount,
FAR const ubyte *wrbuffer);
EXTERN int rwb_mediaremoved(FAR struct rwbuffer_s *rwb);
#undef EXTERN
#if defined(__cplusplus)
}
#endif
#endif /* CONFIG_FS_WRITEBUFFER || CONFIG_READAHEAD_BUFFER */
#endif /* __INCLUDE_NUTTX_RWBUFFER_H */