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1998334d5a
Create doc/usage/filesystems/ section. Convert doc/README.ext4 to rST format and move it to the new section. Update documentation to add configuration instruction for Ext4 Write when using large partitions. Note that this patch depends on this previous patch: https://patchwork.ozlabs.org/project/uboot/patch/20250910215702.15576-1-mibodhi@gmail.com/ Signed-off-by: Tony Dinh <mibodhi@gmail.com> Reviewed-by: Anshul Dalal <anshuld@ti.com>
138 lines
3.0 KiB
ReStructuredText
138 lines
3.0 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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Ext4 File System
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================
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Overview
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--------
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U-Boot supports access of both ext2 and ext4 filesystems, either in read-only
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mode or in read-write mode.
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Configuration
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-------------
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First, to enable support for both ext4 (and, automatically, ext2 as well),
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but without selecting the corresponding commands, enable one of the following:
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::
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CONFIG_FS_EXT4 (for read-only)
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CONFIG_EXT4_WRITE (for read-write)
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Next, to select the ext2-related commands:
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* ext2ls
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* ext2load
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or ext4-related commands:
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* ext4size
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* ext4ls
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* ext4load
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use one or both of:
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::
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CONFIG_CMD_EXT2
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CONFIG_CMD_EXT4
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Selecting either of the above automatically selects CONFIG_FS_EXT4 if it
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wasn't enabled already.
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In addition, to get the write access command ``ext4write``, enable:
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::
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CONFIG_CMD_EXT4_WRITE
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which automatically selects CONFIG_EXT4_WRITE if it wasn't defined
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already.
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Also relevant are the generic filesystem commands, selected by:
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::
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CONFIG_CMD_FS_GENERIC
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This does not automatically enable EXT4 support for you, you still need
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to do that yourself.
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Lastly, the current u-boot implementation for Ext4 write requires a lot
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of memory to run successfully. The following enable support for
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large Ext4 partitions:
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::
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CONFIG_EXT4_MAX_JOURNAL_ENTRIES
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CONFIG_SYS_MALLOC_LEN
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The number of journal entries and dynamic memory allocation are proportional
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to the partition capacity. For example, an ext4 4TB HDD partition could
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require approximately 500 entries and more than 128 MB heap space.
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Examples
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--------
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Some sample commands to test ext4 support:
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1. Check that the ext4 commands can be seen in the output of U-Boot help:
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::
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=> help
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...
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ext4load- load binary file from a Ext4 file system
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ext4ls - list files in a directory (default /)
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ext4size - determine a file's size
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ext4write- create a file in ext4 formatted partition
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...
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2. The ``ext4ls`` command can be used to list the files in an ext4-formatted partition:
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::
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ext4ls <interface> <dev[:part]> [directory]
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For example, to list files in ext4-formatted partition directory /usr/lib:
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::
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=> ext4ls mmc 0:5 /usr/lib
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3. The ``ext4load`` command can be used to read and load a file from an
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ext4-formatted partition to RAM:
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::
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ext4load <interface> [<dev[:part]> [addr [filename [bytes [pos]]]]]
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For example, to load file /uImage from an ext4-formatted partition:
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::
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=> ext4load mmc 2:2 0x30007fc0 uImage
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4. The ``ext4write`` command can be used to write to an ext4 partition:
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::
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ext4write <interface> <dev[:part]> <addr> <absolute filename path> [sizebytes] [file offset]
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For example, to write a file loaded at 0x8200000 of size 256 bytes to an
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ext4-formatted partition with the filename ``/boot/sample_file.hex``:
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::
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=> ext4write mmc 2:2 0x82000000 /boot/sample_file.hex 0x100
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256 bytes written in 138 ms (1000 Bytes/s)
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References
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----------
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* ext4 implementation in Linux Kernel
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* Uboot existing ext2 load and ls implementation
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* Journaling block device JBD2 implementation in linux Kernel
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