Merge tag 'doc-next-2025-09-27' of https://source.denx.de/u-boot/custodians/u-boot-efi into next
Pull request doc-next-2025-09-27 CI: * https://source.denx.de/u-boot/custodians/u-boot-efi/-/pipelines/27746 Documentation: * Move ext4 documentation to HTML. * Describe configuration option EXT4_MAX_JOURNAL_ENTRIES and memory ext4 journal memory requirements.
This commit is contained in:
Tom Rini
@@ -1,83 +0,0 @@
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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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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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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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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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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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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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Some sample commands to test ext4 support:
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1. Check that the commands can be seen in the output of U-Boot help:
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UBOOT #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. To list the files in an ext4-formatted partition, run:
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ext4ls <interface> <dev[:part]> [directory]
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For example:
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UBOOT #ext4ls mmc 0:5 /usr/lib
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3. To read and load a file from an ext4-formatted partition to RAM, run:
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ext4load <interface> <dev[:part]> [addr] [filename] [bytes]
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For example:
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UBOOT #ext4load mmc 2:2 0x30007fc0 uImage
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4. To write a file to an ext4-formatted partition.
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a) First load a file to RAM at a particular address for example 0x30007fc0.
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Now execute ext4write command:
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ext4write <interface> <dev[:part]> [filename] [Address] [sizebytes]
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For example:
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UBOOT #ext4write mmc 2:2 /boot/uImage 0x30007fc0 6183120
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(here 6183120 is the size of the file to be written)
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Note: Absolute path is required for the file to be written
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References :
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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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@@ -0,0 +1,137 @@
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.. 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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@@ -147,3 +147,11 @@ Booting OS
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os/plan9
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os/vxworks
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File Systems
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------------
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.. toctree::
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:maxdepth: 1
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filesystems/ext4
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