/****************************************************************************
* 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 <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"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: mkfatfs_nfatsect12
*
* Description:
* Calculate the number of sectors need for the 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 total size of the 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 = nfats * (1.5 * (ndataclust + 2) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = nfats * (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 fmt->ff_nfats * (numer + denom - 1) / denom;
}
else
{
return 0;
}
}
/****************************************************************************
* Name: mkfatfs_nfatsect16
*
* Description:
* Calculate the number of sectors need for the 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 total size of the 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 = nfats * (2 * (ndataclust + 2) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = nfats * (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 fmt->ff_nfats * (numer + denom - 1) / denom;
}
/****************************************************************************
* Name: mkfatfs_nfatsect32
*
* Description:
* Calculate the number of sectors need for the 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 total size of the 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 = nfats * (4 * (ndataclust + 3) / sectorsize)
*
* where:
*
* ndataclust = ndatasect / clustsize
* nvailsects = nfatsects + ndatasect
*
* The solution to this set of linear equations is:
*
* nfatsects = nfats * (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 fmt->ff_nfats * (numer + denom - 1) / denom;
}
/****************************************************************************
* 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;
}
