[PATCH] exfat: doc: add documentation

[Namjae Jeon <linkinjeon@kernel.org>]

Add documentation for the Linux exFAT filesystem driver, including
supported mount options and exfatprogs.

Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
---
 Documentation/filesystems/exfat.rst | 117 ++++++++++++++++++++++++++++
 Documentation/filesystems/index.rst |   1 +
 2 files changed, 118 insertions(+)
 create mode 100644 Documentation/filesystems/exfat.rst

diff --git a/Documentation/filesystems/exfat.rst b/Documentation/filesystems/exfat.rst
new file mode 100644
index 000000000000..ce5c9344a7b2
--- /dev/null
+++ b/Documentation/filesystems/exfat.rst
@@ -0,0 +1,117 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================================
+The Linux exFAT filesystem driver
+==================================
+
+
+.. Table of contents
+
+   - Overview
+   - Utilities support
+   - Supported mount options
+
+
+Overview
+========
+
+exFAT is a filesystem designed for removable storage and other devices that
+need to store large files.  The Linux exFAT filesystem driver provides read
+and write support for exFAT volumes.
+
+To mount an exFAT volume, use the ``exfat`` filesystem type::
+
+  mount -t exfat /dev/sdX1 /mnt
+
+
+Utilities support
+=================
+
+The exfatprogs project provides userspace utilities for creating, checking,
+repairing, inspecting, and tuning exFAT filesystems.  Use exfatprogs when
+creating or checking an exFAT filesystem.  For example, use ``mkfs.exfat``
+to create a filesystem and ``fsck.exfat`` to check or repair one.
+
+The project is available at:
+
+  https://github.com/exfatprogs/exfatprogs
+
+
+Supported mount options
+=======================
+
+The exFAT driver supports the following mount options:
+
+======================= ====================================================
+uid=
+gid=                    Set the owner and group of all files and
+                        directories.  The default is the uid and gid of
+                        the process mounting the filesystem.
+
+umask=                  Set the permission mask for files and directories.
+                        The default is the umask of the process mounting
+                        the filesystem.
+
+dmask=                  Set the permission mask for directories.
+
+fmask=                  Set the permission mask for files.
+
+allow_utime=            Control the permission check for changing file
+                        timestamps.  Only permission bits 0022 are used.
+                        Permission bit 0020 allows members of the file's
+                        group to change timestamps, and permission bit 0002
+                        allows other users to change timestamps.  The
+                        default is derived from dmask (``~dmask & 0022``).
+
+iocharset=name          Character set used to convert between user-visible
+                        filenames and the UTF-16 character encoding used by
+                        exFAT.  The default is
+                        CONFIG_EXFAT_DEFAULT_IOCHARSET, which is ``utf8``
+                        unless changed at kernel configuration time.  Use
+                        ``iocharset=utf8`` for UTF-8 filename handling.
+
+errors=                 Specify exFAT behavior on filesystem errors.  The
+                        value must be ``panic``, ``continue``, or
+                        ``remount-ro``.  These respectively panic, continue
+                        without changing the filesystem, or remount the
+                        filesystem read-only.  The default is
+                        ``remount-ro``.
+
+discard                 Issue discard/TRIM requests to the block device
+                        when clusters are freed.  This is disabled by
+                        default.  ``nodiscard`` disables it explicitly.
+
+keep_last_dots          Keep trailing periods in path components during
+                        lookup.  Without this option, trailing periods are
+                        stripped.  Existing entries with trailing periods
+                        can be accessed when this option is enabled, but
+                        creating new entries with trailing periods is
+                        rejected.
+
+sys_tz                  Use the system timezone as the UTC offset when an
+                        exFAT timestamp does not contain a valid timezone
+                        offset.  This takes precedence over time_offset.
+
+time_offset=minutes     Set the UTC offset, in minutes, used when an exFAT
+                        timestamp does not contain a valid timezone offset.
+                        Values from -1440 to 1440 are accepted.  The default
+                        is 0.  This option is ignored when sys_tz is set.
+
+zero_size_dir           Create directories with zero size and without
+                        allocating a cluster.  This is disabled by default;
+                        the default behavior allocates a cluster for a new
+                        directory.  ``nozero_size_dir`` disables it
+                        explicitly.
+======================= ====================================================
+
+
+Deprecated mount options
+------------------------
+
+The following options are accepted for compatibility but should not be used:
+
+``utf8``
+  Deprecated.  Use ``iocharset=utf8`` instead.
+
+``debug``, ``namecase=``, ``codepage=``
+  Deprecated and ignored by the exFAT driver.
diff --git a/Documentation/filesystems/index.rst b/Documentation/filesystems/index.rst
index 734a45e51667..fbd55915a318 100644
--- a/Documentation/filesystems/index.rst
+++ b/Documentation/filesystems/index.rst
@@ -87,6 +87,7 @@ Documentation for filesystem implementations.
    ecryptfs
    efivarfs
    erofs
+   exfat
    ext2
    ext3
    ext4/index
-- 
2.25.1