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Date:      Sun, 16 Oct 2011 10:50:02 -0600
From:      Ian Lepore <freebsd@damnhippie.dyndns.org>
To:        mrossi@swin.edu.au
Cc:        freebsd-arm@freebsd.org
Subject:   Re: Create FAT partition/filesystem on the internal microSD flash of the Dreamplug
Message-ID:  <1318783802.2245.8.camel@revolution.hippie.lan>
In-Reply-To: <4E9669CB.2060707@swin.edu.au>
References:  <4E9290FF.7090306@swin.edu.au> <cone.1318239903.356917.1719.500@rlydontknow> <4E92D2D8.8070500@swin.edu.au> <4E9535D0.2030706@swin.edu.au> <A0FE69B0-B12F-43BA-9881-FFF96AAEB007@bsdimp.com> <4E9669CB.2060707@swin.edu.au>
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On Thu, 2011-10-13 at 15:32 +1100, Mattia Rossi wrote:
> On 13/10/11 02:06, Warner Losh wrote:
> >
> > On Oct 12, 2011, at 12:38 AM, Mattia Rossi wrote:
> >
> >> -snip-
> >>>>> I've tried to recreate it using gpart and newfs_msdos, but can't
> >>>>> create any new FAT partition that mount_msdosfs would mount.
> >>>>> [snip]

This turned out to be a difference in structure packing (it's something
that happens a lot with ARM).  The patch below should get it working for
you.

Funny aside:  I opened newfs_msdos.c and within 90 seconds knew what was
wrong and how to fix it.  It then took me over an hour to prove to
myself that my fix was right -- the mount was failing because I forgot
to put "option MSDOSFS" in my kernel config (and we always build our
systems with no .ko modules at all).

-- Ian

diff -r 0e647646c002 sbin/newfs_msdos/newfs_msdos.c
--- sbin/newfs_msdos/newfs_msdos.c.orig	Thu Sep 29 08:39:38 2011 -0600
+++ sbin/newfs_msdos/newfs_msdos.c	Sun Oct 16 10:40:07 2011 -0600
@@ -98,7 +98,7 @@ static const char rcsid[] =
 struct bs {
     u_int8_t bsJump[3];		/* bootstrap entry point */
     u_int8_t bsOemName[8];		/* OEM name and version */
-};
+} __packed;
 
 struct bsbpb {
     u_int8_t bpbBytesPerSec[2];		/* bytes per sector */
@@ -113,7 +113,7 @@ struct bsbpb {
     u_int8_t bpbHeads[2];		/* drive heads */
     u_int8_t bpbHiddenSecs[4];		/* hidden sectors */
     u_int8_t bpbHugeSectors[4];		/* big total sectors */
-};
+} __packed;
 
 struct bsxbpb {
     u_int8_t bpbBigFATsecs[4];		/* big sectors per FAT */
@@ -123,7 +123,7 @@ struct bsxbpb {
     u_int8_t bpbFSInfo[2];		/* file system info sector */
     u_int8_t bpbBackup[2];		/* backup boot sector */
     u_int8_t bpbReserved[12];			/* reserved */
-};
+} __packed;
 
 struct bsx {
     u_int8_t exDriveNumber;		/* drive number */
@@ -132,7 +132,7 @@ struct bsx {
     u_int8_t exVolumeID[4];		/* volume ID number */
     u_int8_t exVolumeLabel[11]; 	/* volume label */
     u_int8_t exFileSysType[8];		/* file system type */
-};
+} __packed;
 
 struct de {
     u_int8_t deName[11];	/* name and extension */
@@ -142,7 +142,7 @@ struct de {
     u_int8_t deMDate[2];	/* creation date */
     u_int8_t deStartCluster[2];	/* starting cluster */
     u_int8_t deFileSize[4];	/* size */
-};
+} __packed;
 
 struct bpb {
     u_int bpbBytesPerSec;		/* bytes per sector */
help

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