From victor at couty.eu  Sat May  9 22:08:34 2026
From: victor at couty.eu (Victor Couty)
Date: Sat, 9 May 2026 23:08:34 +0200
Subject: [parted-devel] ExFAT support
In-Reply-To: <36933605-b100-4bbd-8610-bad94486c888@plouf.fr.eu.org>
References: <a3140d44-d26e-4cf9-8225-20a16cb3e397@couty.eu>
 <ab26YtaDaZV0tEnr@ohop.brianlane.com>
 <36933605-b100-4bbd-8610-bad94486c888@plouf.fr.eu.org>
Message-ID: <e6bec3ce-bc97-4087-a956-d1a2f0cc4bd4@couty.eu>

Here is the fixed version of the patch. Pascal was correct: t1700 
formats the entire device and msdos probe is executed first, returning a 
false positive for an msdos label. My previous testing only included an 
actual partition so i missed this case. I updated msdos_probe to add the 
check just like FAT and NTFS. A full-disk ExFAT fs is now properly 
detected and all tests are passing. ExFAT implementation ended up being 
very similar to NTFS.

 From 9b8d067bba75b183fae0f685a4cdb80492118ede Mon Sep 17 00:00:00 2001
From: Victor Couty<victor at couty.eu>
Date: Wed, 31 Dec 2025 07:58:53 +0100
Subject: [PATCH] Adding support for ExFAT filesystem

Added and registered exfat probing function
Updated msdos label probe to properly detect full-disk exfat fs
Reflected ExFAT support in doc
Added ExFAT detection test in t1700-probe-fs.sh
---
  doc/C/parted.8             |  2 +-
  doc/parted.texi            |  1 +
  libparted/fs/Makefile.am   |  1 +
  libparted/fs/exfat/exfat.c | 74 ++++++++++++++++++++++++++++++++++++++
  libparted/labels/dos.c     |  6 ++++
  libparted/libparted.c      |  4 +++
  tests/t1700-probe-fs.sh    |  2 +-
  7 files changed, 88 insertions(+), 2 deletions(-)
  create mode 100644 libparted/fs/exfat/exfat.c

diff --git a/doc/C/parted.8 b/doc/C/parted.8
index 359b046..40e6212 100644
--- a/doc/C/parted.8
+++ b/doc/C/parted.8
@@ -82,7 +82,7 @@ should be one of "aix", "amiga", "bsd", "dvh", "gpt", "loop", "mac", "msdos",
  Create a new partition. \fIpart-type\fP may be specified only with msdos and
  dvh partition tables, it should be one of "primary", "logical", or "extended".
  \fIname\fP is required for GPT partition tables and \fIfs-type\fP is optional.
-\fIfs-type\fP can be one of "btrfs", "ext2", "ext3", "ext4", "fat16", "fat32",
+\fIfs-type\fP can be one of "btrfs", "exfat", "ext2", "ext3", "ext4", "fat16", "fat32",
  "hfs", "hfs+", "linux-swap", "ntfs", "reiserfs", "udf", or "xfs".
  .TP
  .B name \fIpartition\fP \fIname\fP
diff --git a/doc/parted.texi b/doc/parted.texi
index 4123b2c..10a576b 100644
--- a/doc/parted.texi
+++ b/doc/parted.texi
@@ -624,6 +624,7 @@ partition table.
  @itemize @bullet
  @item btrfs
  @item ext2, ext3, ext4
+ at item exfat
  @item fat16, fat32
  @item hfs, hfs+, hfsx
  @item hp-ufs
diff --git a/libparted/fs/Makefile.am b/libparted/fs/Makefile.am
index 2cfe425..43116db 100644
--- a/libparted/fs/Makefile.am
+++ b/libparted/fs/Makefile.am
@@ -28,6 +28,7 @@ libfs_la_SOURCES =		\
    ext2/ext2.h			\
    ext2/ext2_fs.h		\
    ext2/interface.c		\
+  exfat/exfat.c			\
    fat/bootsector.c		\
    fat/bootsector.h		\
    fat/count.h			\
diff --git a/libparted/fs/exfat/exfat.c b/libparted/fs/exfat/exfat.c
new file mode 100644
index 0000000..0caee12
--- /dev/null
+++ b/libparted/fs/exfat/exfat.c
@@ -0,0 +1,74 @@
+/*
+libparted
+    Copyright (C) 1998-2000, 2002, 2004, 2007, 2009-2014, 2019-2023 Free
+    Software Foundation, Inc.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see<http://www.gnu.org/licenses/>.
+*/
+
+#include <config.h>
+
+#include <parted/parted.h>
+#include <parted/endian.h>
+
+#include <unistd.h>
+
+#define EXFAT_SIGNATURE "EXFAT   "
+
+PedGeometry* exfat_probe (PedGeometry* geom)
+{
+    uint8_t *buf = alloca(geom->dev->sector_size);
+
+    if (!ped_geometry_read(geom, buf, 0, 1)) {
+        return NULL;
+    }
+    if (strncmp (EXFAT_SIGNATURE, ((char *)buf + 3), strlen (EXFAT_SIGNATURE)) == 0) {
+        uint64_t sector_count;
+        unsigned char bytes_per_sector_shift;
+        uint64_t fs_size;
+        PedGeometry *newg = NULL;
+
+        memcpy(&sector_count, buf + 0x48, sizeof(uint64_t));
+        memcpy(&bytes_per_sector_shift, buf + 0x6c, sizeof(unsigned char));
+        if (bytes_per_sector_shift < 9 || bytes_per_sector_shift > 12) {
+            return NULL;
+        }
+        fs_size = sector_count * (1ULL << bytes_per_sector_shift);
+        newg = ped_geometry_new(geom->dev, geom->start, fs_size);
+
+        return newg;
+    }
+
+    return NULL;
+}
+
+static PedFileSystemOps exfat_ops = {
+    probe: exfat_probe,
+};
+
+static PedFileSystemType exfat_type = {
+    next: NULL,
+    ops: &exfat_ops,
+    name: "exfat",
+};
+
+void ped_file_system_exfat_init()
+{
+    ped_file_system_type_register (&exfat_type);
+}
+
+void ped_file_system_exfat_done ()
+{
+    ped_file_system_type_unregister (&exfat_type);
+}
diff --git a/libparted/labels/dos.c b/libparted/labels/dos.c
index 9f88618..5680624 100644
--- a/libparted/labels/dos.c
+++ b/libparted/labels/dos.c
@@ -439,6 +439,9 @@ fat_probe_fat32 (PedGeometry* geom);
  PedGeometry*
  ntfs_probe (PedGeometry* geom);
  
+PedGeometry*
+exfat_probe (PedGeometry* geom);
+
  static int
  msdos_probe (const PedDevice *dev)
  {
@@ -474,6 +477,9 @@ msdos_probe (const PedDevice *dev)
  	fsgeom = ntfs_probe (geom);
  	if (fsgeom)
  		goto probe_fail; /* ntfs fs looks like dos mbr */
+	fsgeom = exfat_probe (geom);
+	if (fsgeom)
+		goto probe_fail; /* exfat fs looks like dos mbr */
  	ped_geometry_destroy (geom);
  	geom = NULL;
  
diff --git a/libparted/libparted.c b/libparted/libparted.c
index 4dabb7e..b180528 100644
--- a/libparted/libparted.c
+++ b/libparted/libparted.c
@@ -115,6 +115,7 @@ extern void ped_file_system_ext2_init (void);
  extern void ped_file_system_nilfs2_init (void);
  extern void ped_file_system_btrfs_init (void);
  extern void ped_file_system_udf_init (void);
+extern void ped_file_system_exfat_init (void);
  
  static void
  init_file_system_types ()
@@ -133,6 +134,7 @@ init_file_system_types ()
  	ped_file_system_nilfs2_init ();
  	ped_file_system_btrfs_init ();
  	ped_file_system_udf_init ();
+	ped_file_system_exfat_init ();
  }
  
  extern void ped_disk_aix_done ();
@@ -200,6 +202,7 @@ extern void ped_file_system_xfs_done (void);
  extern void ped_file_system_amiga_done (void);
  extern void ped_file_system_btrfs_done (void);
  extern void ped_file_system_udf_done (void);
+extern void ped_file_system_exfat_done (void);
  
  static void
  done_file_system_types ()
@@ -218,6 +221,7 @@ done_file_system_types ()
  	ped_file_system_amiga_done ();
  	ped_file_system_btrfs_done ();
  	ped_file_system_udf_done ();
+	ped_file_system_exfat_done ();
  }
  
  static void _done() __attribute__ ((destructor));
diff --git a/tests/t1700-probe-fs.sh b/tests/t1700-probe-fs.sh
index 9b88656..a494e8a 100755
--- a/tests/t1700-probe-fs.sh
+++ b/tests/t1700-probe-fs.sh
@@ -23,7 +23,7 @@ dev=loop-file
  ss=$sector_size_
  n_sectors=$((512*1024))
  
-for type in ext2 ext3 ext4 btrfs xfs nilfs2 ntfs vfat hfsplus udf f2fs; do
+for type in ext2 ext3 ext4 btrfs xfs nilfs2 ntfs vfat hfsplus udf f2fs exfat; do
  
    ( mkfs.$type 2>&1 | grep -i '^usage' ) > /dev/null \
        || { warn_ "$ME: no $type support"; continue; }
-- 
2.54.0



On 21/03/2026 ? 11:59, Pascal Hambourg wrote :
> On 20/03/2026 at 22:21, Brian C. Lane wrote:
>> On Sat, Feb 14, 2026 at 05:37:27PM +0100, Victor Couty wrote:
>>>
>>> I would like to add support for the ExFAT filesystem to parted. This
>>> includes displaying correctly ExFAT partitions and interpreting 
>>> "exfat" as a
>>> correct entry when specifying the fs type upon partition creation.
>>
>> Thanks, a couple things -- your email mangled the patch (seems to be
>> missing some blank lines) so it didn't apply cleanly. It also needs
>> tests, at least t1700 needs to check that it is detected correctly. I
>> threw this in quickly and discovery isn't working right, it is reported
>> as msdos.
>
> IIUC t1700 creates the filesystem in the entire device (not in a 
> partition), so I suspect that parted probes disk labels first and 
> msdos_probe() wrongly detects a msdos label and should be patched to 
> exclude exFAT as it does with FAT.
>
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