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Date: Wed, 28 Sep 2005 00:05:34 -0600
From: Scott Long <scottl@samsco.org>
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To: Mikhail Teterin <mi@corbulon.video-collage.com>
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Cc: re@freebsd.org, peadar.edwards@gmail.com, fs@freebsd.org,
	gayn.winters@bristolsystems.com
Subject: Re: can not mount a large FAT32 filesystem
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Mikhail Teterin wrote:
> Thank you very much, Peter!
> 
> Your patch below makes the card "mountable" and usable. I'm copying
> my photos right now.
> 
> I think, this should be merged into 6.0 -- these cards are a popular
> item... Thanks, again!
> 
> 	-mi
> 
> Index: msdosfs_vfsops.c
> ===================================================================
> RCS file: /nfs/dyson/export/home/petere/freebsd-cvs/cvs/FreeBSD/src/sys/fs/msdosfs/msdosfs_vfsops.c,v
> retrieving revision 1.144
> diff -u -r1.144 msdosfs_vfsops.c
> --- msdosfs_vfsops.c	24 Mar 2005 07:36:13 -0000	1.144
> +++ msdosfs_vfsops.c	27 Sep 2005 09:40:19 -0000
> @@ -512,9 +512,7 @@
>  #endif	/* !MSDOSFS_LARGE */
>  
>  	if (pmp->pm_RootDirEnts == 0) {
> -		if (bsp->bs710.bsBootSectSig2 != BOOTSIG2
> -		    || bsp->bs710.bsBootSectSig3 != BOOTSIG3
> -		    || pmp->pm_Sectors
> +		if (pmp->pm_Sectors
>  		    || pmp->pm_FATsecs
>  		    || getushort(b710->bpbFSVers)) {
>  			error = EINVAL;

Might this be an attempt by the manufacturer to avoid the potential
patent litigation from using msdosfs?  I.e. create a slightly
non-conformant filesystem so that it can't claim to explicitely be
msdosfs/vfat/fat32/whatever, thereby avoiding the patents on those
technologies?

Since these checks are done after other magic number checks, it's likely
safe.  I'm fine with it going into RELENG_6 once it hass been committed
to HEAD.

Scott