[RFC][FAT] Handle MBR on the first sector

[Sascha Hauer]

On Fri, Sep 14, 2012 at 09:22:07AM +0200, Franck Jullien wrote:
> 2012/9/14 Sascha Hauer <s.hauer at pengutronix.de>:
> > Hi Franck,
> >
> > On Thu, Sep 13, 2012 at 02:13:29PM +0200, Franck Jullien wrote:
> >> *** Did not send this email with git because it's no working where I am **
> >>
> >> We may have some disk with MBR as a first sector. In this case, the
> >> current FAT check returns an error. However, the FAT sector exist and
> >> the MBR can tell us where it is.
> >>
> >> This patch make the FAT fs try to find the FAT boot sector on the first
> >> sector of the first partition in case it is not on sector 0.
> >
> > The patch looks good. Not applying it because it's RFC, but I would if
> > you give your ok.
> >
> 
> You have it.

Thanks, applied

Sascha

> 
> > Sascha
> >
> >>
> >> Signed-off-by: Franck Jullien <franck.jullien at gmail.com>
> >> ---
> >>  fs/fat/ff.c |   24 ++++++++++++++++++++----
> >>  1 files changed, 20 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/fs/fat/ff.c b/fs/fat/ff.c
> >> index 66db1d6..6a4ae32 100644
> >> --- a/fs/fat/ff.c
> >> +++ b/fs/fat/ff.c
> >> @@ -191,6 +191,7 @@
> >>  #define      FSI_Nxt_Free            492     /* FSI: Last allocated cluster (4) */
> >>  #define MBR_Table            446     /* MBR: Partition table offset (2) */
> >>  #define      SZ_PTE                  16      /* MBR: Size of a partition table entry */
> >> +#define MBR_StartSector              8       /* MBR: Offset of Starting Sector in
> >> Partition Table Entry */
> >>  #define BS_55AA                      510     /* Boot sector signature (2) */
> >>
> >>  #define      DIR_Name                0       /* Short file name (11) */
> >> @@ -1533,11 +1534,15 @@ int follow_path (     /* 0(0): successful, !=0:
> >> error code */
> >>   */
> >>  static int check_fs (        /* 0:The FAT BR, 1:Valid BR but not an FAT,
> >> 2:Not a BR, 3:Disk error */
> >>       FATFS *fs,      /* File system object */
> >> -     DWORD sect      /* Sector# (lba) to check if it is an FAT boot record or not */
> >> +     DWORD sect,     /* Sector# (lba) to check if it is an FAT boot record or not */
> >> +     DWORD *bootsec
> >>  )
> >>  {
> >>       int ret;
> >>
> >> +     if(bootsec)
> >> +             *bootsec = 0;
> >> +
> >>       /* Load boot record */
> >>       ret = disk_read(fs, fs->win, sect, 1);
> >>       if (ret)
> >> @@ -1553,6 +1558,12 @@ static int check_fs (  /* 0:The FAT BR, 1:Valid
> >> BR but not an FAT, 2:Not a BR, 3:
> >>       if ((LD_DWORD(&fs->win[BS_FilSysType32]) & 0xFFFFFF) == 0x544146)
> >>               return 0;
> >>
> >> +     if(bootsec)
> >> +             /* This must be an MBR, so return the starting sector of the
> >> +              * first partition so we could check if there is a FAT boot
> >> +              * sector there */
> >> +             *bootsec = LD_WORD(&fs->win[MBR_Table + MBR_StartSector]);
> >> +
> >>       return -ENODEV;
> >>  }
> >>
> >> @@ -1565,6 +1576,7 @@ static int chk_mounted (        /* 0(0): successful,
> >> !=0: any error occurred */
> >>  )
> >>  {
> >>       BYTE fmt, b;
> >> +     DWORD first_boot_sect;
> >>       DWORD bsect, fasize, tsect, sysect, nclst, szbfat;
> >>       WORD nrsv;
> >>
> >> @@ -1579,9 +1591,13 @@ static int chk_mounted (       /* 0(0): successful,
> >> !=0: any error occurred */
> >>               return -EIO;
> >>  #endif
> >>       /* Search FAT partition on the drive. Supports only generic
> >> partitionings, FDISK and SFD. */
> >> -     fmt = check_fs(fs, bsect = 0);  /* Check sector 0 if it is a VBR */
> >> -     if (fmt)
> >> -             return fmt; /* No FAT volume is found */
> >> +     fmt = check_fs(fs, bsect = 0, &first_boot_sect);        /* Check sector 0
> >> if it is a VBR */
> >> +     if (fmt && first_boot_sect != 0) {
> >> +             /* Sector 0 is an MBR, now check for FAT in the first partition */
> >> +             fmt = check_fs(fs, bsect = first_boot_sect, NULL);
> >> +             if(fmt)
> >> +                     return fmt; /* No FAT volume is found */
> >> +     }
> >>
> >>       /* Following code initializes the file system object */
> >>
> >> --
> >> 1.7.1
> >>
> >> _______________________________________________
> >> barebox mailing list
> >> barebox at lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/barebox
> >>
> >
> > --
> > Pengutronix e.K.                           |                             |
> > Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |
> 

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |