/****************************************************************************
* fs/fat/fs_configfat.c
*
* Copyright (C) 2008 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 <string.h>
#include <debug.h>
#include <errno.h>
#include <nuttx/fs.h>
#include <nuttx/fat.h>
#include <nuttx/mkfatfs.h>
#include "fs_internal.h"
#include "fs_fat32.h"
#include "fs_mkfatfs.h"
/****************************************************************************
* Definitions
****************************************************************************/
#define NDX12 0
#define NDX16 1
#define NDX32 2
#define fatconfig12 fatconfig[NDX12]
#define fatconfig16 fatconfig[NDX16]
#define fatconfig32 fatconfig[NDX32]
/****************************************************************************
* Private Types
****************************************************************************/
struct fat_config_s
{
uint32 fc_navailsects; /* The number of available sectors */
uint32 fc_nfatsects; /* The number of sectors in one FAT */
uint32 fc_nclusters; /* The number of clusters in the filesystem */
};
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: mkfatfs_nfatsect12
*
* Description:
* Calculate the number of sectors need for one fat in a FAT12 file system.
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* navailsects - The number of sectors available for both FAT and data.
* This is a precalculated value equal to the total number of sectors
* minus the number of root directory sectors and minus the number of
* reserved sectors.
*
* Return:
* 0: That calculation would have overflowed
* >0: The size of one FAT in sectors.
*
****************************************************************************/
static inline uint32
mkfatfs_nfatsect12(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
uint32 navailsects)
{
uint32 denom ;
uint32 numer;
/* For FAT12, the cluster number is held in a 12-bit number or 1.5 bytes per
* cluster reference. So each FAT sector will hold sectorsize/1.5 cluster
* references (except for the first sector of each FAT which has two reserved
* 12-bit values). And the total number of FAT sectors needed is:
*
* nfatsects = (1.5 * (ndataclust + 2) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = (3 * navailsects + 6 * clustersize) /
* (3 * nfats + 2 * sectorsize * clustersize)
*
* The numerator would overflow uint32 if:
*
* 3 * navailsects + 6 * clustersize > 0xffffffff
*
* Or
*
* navailsects > 0x55555555 - 2 * clustersize
*/
if (navailsects <= (0x55555555 - (1 << (fmt->ff_clustshift + 1))))
{
denom = (fmt->ff_nfats << 1) + fmt->ff_nfats
+ (var->fv_sectorsize << (fmt->ff_clustshift + 1));
numer = (navailsects << 1) + navailsects
+ (1 << (fmt->ff_clustshift + 2)) + (1 << (fmt->ff_clustshift + 1));
return (numer + denom - 1) / denom;
}
else
{
return 0;
}
}
/****************************************************************************
* Name: mkfatfs_nfatsect16
*
* Description:
* Calculate the number of sectors need for one fat in a FAT16 file system.
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* navailsects - The number of sectors available for both FAT and data.
* This is a precalculated value equal to the total number of sectors
* minus the number of root directory sectors and minus the number of
* reserved sectors.
*
* Return:
* The size of one FAT in sectors.
*
****************************************************************************/
static inline uint32
mkfatfs_nfatsect16(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
uint32 navailsects)
{
uint32 denom;
uint32 numer;
/* For FAT16, the cluster number is held in a 16-bit number or 2 bytes per
* cluster reference. So each FAT sector will hold sectorsize/2 cluster
* references (except for the first sector of each FAT which has two reserved
* 16-bit values). And the total number of FAT sectors needed is:
*
* nfatsects = (2 * (ndataclust + 2) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = (navailsects + 2 * clustersize) /
* (nfats + sectorsize * clustersize / 2)
*
* Overflow in the calculation of the numerator could occur if:
*
* navailsects > 0xffffffff - 2 * clustersize
*/
if (fmt->ff_clustshift == 0)
{
denom = fmt->ff_nfats + (var->fv_sectorsize >> 1);
numer = navailsects + 2;
}
else
{
denom = fmt->ff_nfats + (var->fv_sectorsize << (fmt->ff_clustshift - 1));
numer = navailsects + (1 << (fmt->ff_clustshift + 1));
}
return (numer + denom - 1) / denom;
}
/****************************************************************************
* Name: mkfatfs_nfatsect32
*
* Description:
* Calculate the number of sectors need for one fat in a FAT32 file system.
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* navailsects - The number of sectors available for both FAT and data.
* This is a precalculated value equal to the total number of sectors
* minus the number of root directory sectors and minus the number of
* reserved sectors.
*
* Return:
* The size of one FAT in sectors.
*
****************************************************************************/
static inline uint32
mkfatfs_nfatsect32(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
uint32 navailsects)
{
uint32 denom;
uint32 numer;
/* For FAT32, the cluster number is held in a 32-bit number or 4 bytes per
* cluster reference. So each FAT sector will hold sectorsize/4 cluster
* references (except for the first sector of each FAT which has three reserved
* 32-bit values). And the total number of FAT sectors needed is:
*
* nfatsects = (4 * (ndataclust + 3) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = (navailsects + 3 * clustersize) /
* (nfats + sectorsize * clustersize / 4)
*
* Overflow in the calculation of the numerator could occur if:
*
* navailsects > 0xffffffff - 3 * clustersize
*/
if (fmt->ff_clustshift == 0)
{
denom = fmt->ff_nfats + (var->fv_sectorsize >> 2);
numer = navailsects + 3;
}
else if (fmt->ff_clustshift == 1)
{
denom = fmt->ff_nfats + (var->fv_sectorsize >> 1);
numer = navailsects + 6;
}
else
{
denom = fmt->ff_nfats + (var->fv_sectorsize << (fmt->ff_clustshift - 2));
numer = navailsects + (1 << (fmt->ff_clustshift + 1)) + (1 << fmt->ff_clustshift);
}
return (numer + denom - 1) / denom;
}
/****************************************************************************
* Name: mkfatfs_clustersearchlimits
*
* Description:
* Pick the starting and ending cluster size to use in the search for the
* the optimal cluster size.
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
*
* Return:
* Starting cluster size is set in fmt->ff_clustshift; Final cluster
* size is the returned value.
*
****************************************************************************/
static inline ubyte
mkfatfs_clustersearchlimits(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var)
{
ubyte mxclustshift;
/* Did the caller already pick the cluster size? If not, the clustshift value
* will be 0xff
*/
if (fmt->ff_clustshift == 0xff)
{
/* Pick a starting size based on the number of sectors on the device */
if (var->fv_nsectors < 2048)
{
/* 2k sectors, start wit 1 sector/cluster. */
fmt->ff_clustshift = 0;
}
else if (var->fv_nsectors < 4096)
{
/* 4k sectors, start with 2 sector/cluster. */
fmt->ff_clustshift = 1;
}
else if (var->fv_nsectors < 8192)
{
/* 8k sectors, start with 4 sector/cluster. */
fmt->ff_clustshift = 2;
}
else if (var->fv_nsectors < 16384)
{
/* 16k sectors, start with 8 sector/cluster. */
fmt->ff_clustshift = 3;
}
else if (var->fv_nsectors < 32768)
{
/* 32k sectors, start with 16 sector/cluster. */
fmt->ff_clustshift = 4;
}
else
{
/* Otherwise, 32 sector/cluster. */
fmt->ff_clustshift = 5;
}
/* Wherever the search starts, it will end with the maximum of
* 128 sectors per cluster
*/
mxclustshift = 7;
}
else
{
/* The caller has selected a cluster size. There will be no search!
* Just set the maximum to the caller specificed value.
*/
mxclustshift = fmt->ff_clustshift;
}
return mxclustshift;
}
/****************************************************************************
* Name: mkfatfs_try12
*
* Description:
* Try to define a FAT12 filesystem on the device using the candidate
* sectors per cluster
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* fatconfig - FAT12-specific configuration
*
* Return:
* Zero on success configuration of a FAT12 file system; negated errno
* on failure
*
****************************************************************************/
static inline int
mkfatfs_tryfat12(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
FAR struct fat_config_s *config)
{
uint32 maxnclusters;
/* Calculate the number sectors in one FAT required to access all of the
* available sectors.
*/
config->fc_nfatsects = mkfatfs_nfatsect12(fmt, var, config->fc_navailsects);
if (config->fc_nfatsects > 0)
{
/* Calculate the number of clusters available given the number of available
* sectors and the number of those that will be used for FAT:
*/
config->fc_nclusters =
(config->fc_navailsects -
fmt->ff_nfats * config->fc_nfatsects) >> fmt->ff_clustshift;
/* Calculate the maximum number of clusters that could be supported by a
* FAT of this size.
*
* maxnclusters = nfatsects * sectorsize / 1.5 - 2
*/
maxnclusters = (config->fc_nfatsects >> (var->fv_sectshift + 1)) / 3;
if (maxnclusters > FAT_MAXCLUST12)
{
maxnclusters = FAT_MAXCLUST12;
}
fvdbg("nfatsects=%u nclusters=%u (max=%u)\n",
config->fc_nfatsects, config->fc_nclusters, maxnclusters);
/* Check if this number of clusters would overflow the maximum for
* FAT12 (remembering that two FAT cluster slots are reserved).
*/
if (config->fc_nclusters > maxnclusters - 2)
{
fvdbg("Too many clusters for FAT12\n");
return -ENFILE;
}
}
return 0;
}
/****************************************************************************
* Name: mkfatfs_try16
*
* Description:
* Try to define a FAT16 filesystem on the device using the candidate
* sectors per cluster
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* fatconfig - FAT16-specific configuration
*
* Return:
* Zero on success configuration of a FAT16 file system; negated errno
* on failure
*
****************************************************************************/
static inline int
mkfatfs_tryfat16(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
FAR struct fat_config_s *config)
{
uint32 maxnclusters;
/* Calculate the number sectors in one FAT required to access all of the
* available sectors.
*/
config->fc_nfatsects = mkfatfs_nfatsect16(fmt, var, config->fc_navailsects);
if (config->fc_nfatsects > 0)
{
/* Calculate the number of clusters available given the number of available
* sectors and the number of those that will be used for FAT:
*/
config->fc_nclusters =
(config->fc_navailsects -
fmt->ff_nfats * config->fc_nfatsects) >> fmt->ff_clustshift;
/* Calculate the maximum number of clusters that could be supported by a
* FAT of this size.
*
* maxnclusters = nfatsects * sectorsize / 2 - 2
*/
maxnclusters = config->fc_nfatsects << (var->fv_sectorsize - 1);
if (maxnclusters > FAT_MAXCLUST16)
{
maxnclusters = FAT_MAXCLUST16;
}
fvdbg("nfatsects=%u nclusters=%u (min=%u max=%u)\n",
config->fc_nfatsects, config->fc_nclusters, FAT_MINCLUST16, maxnclusters);
/* Check if this number of clusters would overflow the maximum for
* FAT16 (remembering that two FAT cluster slots are reserved).
* Check the lower limit as well. The FAT12 is distinguished from FAT16
* by comparing the number of clusters on the device agains a known
* threshold. If a small FAT16 file system were created, then it would
* be confused as a FAT12 at mount time.
*/
if ((config->fc_nclusters > maxnclusters - 2) ||
(config->fc_nclusters < FAT_MINCLUST16))
{
fvdbg("Too few or too many clusters for FAT16\n");
return -ENFILE;
}
}
return 0;
}
/****************************************************************************
* Name: mkfatfs_try32
*
* Description:
* Try to define a FAT32 filesystem on the device using the candidate
* sectors per cluster
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
* fatconfig - FAT32-specific configuration
*
* Return:
* Zero on success configuration of a FAT32 file system; negated errno
* on failure
*
****************************************************************************/
static inline int
mkfatfs_tryfat32(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var,
FAR struct fat_config_s *config)
{
uint32 maxnclusters;
/* Calculate the number sectors in one FAT required to access all of the
* available sectors.
*/
config->fc_nfatsects = mkfatfs_nfatsect32(fmt, var, config->fc_navailsects);
if (config->fc_nfatsects > 0)
{
/* Calculate the number of clusters available given the number of available
* sectors and the number of those that will be used for FAT:
*/
config->fc_nclusters =
(config->fc_navailsects -
fmt->ff_nfats * config->fc_nfatsects) >> fmt->ff_clustshift;
/* Calculate the maximum number of clusters that could be supported by a
* FAT of this size.
*
* maxnclusters = nfatsects * sectorsize / 4 - 2
*/
maxnclusters = (config->fc_nfatsects >> (var->fv_sectshift - 2));
if (maxnclusters > FAT_MAXCLUST32)
{
maxnclusters = FAT_MAXCLUST32;
}
fvdbg("nfatsects=%u nclusters=%u (max=%u)\n",
config->fc_nfatsects, config->fc_nclusters, maxnclusters);
/* Check if this number of clusters would overflow the maximum for
* FAT32 (remembering that two FAT cluster slots are reserved).
*/
if ((config->fc_nclusters > maxnclusters - 3) ||
(config->fc_nclusters < FAT_MINCLUST32 && fmt->ff_fattype != 32))
{
fvdbg("Too few or too many clusters for FAT32\n");
return -ENFILE;
}
}
return 0;
}
/****************************************************************************
* Name: mkfatfs_clustersearch
*
* Description:
* Search to find the smallest (reasonable) cluster size for the FAT file
* system.
*
* Input:
* fmt - Caller specified format parameters
* var - Other format parameters that are not caller specifiable. (Most
* set by mkfatfs_configfatfs()).
*
* Return:
* Zero on success; negated errno on failure
*
****************************************************************************/
static inline int
mkfatfs_clustersearch(FAR struct fat_format_s *fmt, FAR struct fat_var_s *var)
{
struct fat_config_s fatconfig[3];
uint32 nrootdirsects = 0;
ubyte mxclustshift;
memset(fatconfig, 0, 3*sizeof(struct fat_config_s));
/* Determine the number of sectors needed by the root directory.
* This is a constant value, independent of cluster size for FAT12/16
*/
if (var->fv_fattype != 32)
{
/* Calculate the number of sectors reqired to contain the selected
* number of root directory entries.
*/
nrootdirsects =
((fmt->ff_rootdirentries << DIR_SHIFT) + var->fv_sectorsize - 1) >> var->fv_sectshift;
/* The number of data sectors available (includes the fat itself)
* This value is a constant for FAT12/16, but not FAT32 because the
* size of the root directory cluster changes
*/
fatconfig12.fc_navailsects =
fatconfig16.fc_navailsects =
var->fv_nsectors - nrootdirsects - fmt->ff_rsvdseccount;
}
/* Select an initial and terminal clustersize to use in the search (if these
* values were not provided by the caller)
*/
mxclustshift = mkfatfs_clustersearchlimits(fmt, var);
do
{
fvdbg("Configuring with %d sectors/cluster...\n", 1 << fmt->ff_clustshift);
/* Check if FAT12 has not been excluded */
fatconfig12.fc_nfatsects = 0;
fatconfig12.fc_nclusters = 0;
\
if (var->fv_fattype == 0 || var->fv_fattype == 12)
{
/* Try to configure a FAT12 filesystem with this cluster size */
if (mkfatfs_tryfat12(fmt, var, &fatconfig12) != 0)
{
{
fvdbg("Cannot format FAT12 at %u sectors/cluster\n", 1 << fmt->ff_clustshift);
fatconfig12.fc_nfatsects = 0;
fatconfig12.fc_nclusters = 0;
}
}
}
/* Check if FAT16 has not been excluded */
fatconfig16.fc_nfatsects = 0;
fatconfig16.fc_nclusters = 0;
if (var->fv_fattype == 0 || var->fv_fattype == 16)
{
/* Try to configure a FAT16 filesystem with this cluster size */
if (mkfatfs_tryfat16(fmt, var, &fatconfig16) != 0)
{
{
fvdbg("Cannot format FAT16 at %u sectors/cluster\n", 1 << fmt->ff_clustshift);
fatconfig16.fc_nfatsects = 0;
fatconfig16.fc_nclusters = 0;
}
}
}
/* Check if FAT32 has not been excluded */
fatconfig32.fc_nfatsects = 0;
fatconfig32.fc_nclusters = 0;
if (var->fv_fattype == 0 || var->fv_fattype == 32)
{
/* The number of data sectors available (includes the fat itself)
* This value is a constant with respect to cluster sizefor FAT12/16, but not FAT32
* because the size of the root directory cluster changes with cluster size.
*/
fatconfig32.fc_navailsects = var->fv_nsectors - (1 << fmt->ff_clustshift) - fmt->ff_rsvdseccount;
/* Try to configure a FAT32 filesystem with this cluster size */
if (mkfatfs_tryfat32(fmt, var, &fatconfig32) != 0)
{
{
fvdbg("Cannot format FAT32 at %u sectors/cluster\n", 1 << fmt->ff_clustshift);
fatconfig32.fc_nfatsects = 0;
fatconfig32.fc_nclusters = 0;
}
}
}
/* If any FAT was configured at this sector/cluster setting, then break out now */
if (fatconfig12.fc_nclusters || fatconfig16.fc_nclusters)
{
/* If both FAT12 and FAT16 ar possible, select the one with the largest
* number of clusters (unless one has already been selected)
*/
if (!var->fv_fattype)
{
if (fatconfig16.fc_nclusters > fatconfig12.fc_nclusters)
{
var->fv_fattype = 16;
}
else
{
var->fv_fattype = 12;
}
}
fdbg("Selected FAT%d\n", var->fv_fattype);
/* Then return the appropriate inforamation about the selected
* file system.
*/
if (var->fv_fattype == 12)
{
var->fv_nclusters = fatconfig12.fc_nclusters;
var->fv_nfatsects = fatconfig12.fc_nfatsects;
}
else
{
var->fv_nclusters = fatconfig16.fc_nclusters;
var->fv_nfatsects = fatconfig16.fc_nfatsects;
}
var->fv_nrootdirsects = nrootdirsects;
return OK;
}
else if (fatconfig32.fc_nclusters)
{
/* Select FAT32 if we have not already done so */
var->fv_fattype = 32;
fdbg("Selected FAT%d\n", var->fv_fattype);
var->fv_nclusters = fatconfig32.fc_nclusters;
var->fv_nfatsects = fatconfig32.fc_nfatsects;
var->fv_nrootdirsects = 1 << fmt->ff_clustshift;
return OK;
}
/* Otherwise, bump up the sectors/cluster for the next time around the loop. */
fmt->ff_clustshift++;
}
while (fmt->ff_clustshift <= mxclustshift);
return -ENFILE;
}
/****************************************************************************
* Global Functions
****************************************************************************/
/****************************************************************************
* Name: mkfatfs_configfatfs
*
* Description:
* Based on the geometry of the block device and upon the caller-selected
* values, configure the FAT filesystem for the device.
*
* Input:
* fmt - Caller specified format parameters
* var - Holds disk geomtry data. Also, the location to return FAT
* configuration data
*
* Return:
* Zero on success; negated errno on failure
*
****************************************************************************/
int mkfatfs_configfatfs(FAR struct fat_format_s *fmt,
FAR struct fat_var_s *var)
{
return OK;
}
