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U-Boot supports access of both ext2 and ext4 filesystems, either in read-only
mode or in read-write mode.
First, to enable support for both ext4 (and, automatically, ext2 as well),
but without selecting the corresponding commands, enable one of the following:
CONFIG_FS_EXT4 (for read-only)
CONFIG_EXT4_WRITE (for read-write)
Next, to select the ext2-related commands:
* ext2ls
* ext2load
or ext4-related commands:
* ext4size
* ext4ls
* ext4load
use one or both of:
CONFIG_CMD_EXT2
CONFIG_CMD_EXT4
Selecting either of the above automatically selects CONFIG_FS_EXT4 if it
wasn't enabled already.
In addition, to get the write access command "ext4write", enable:
CONFIG_CMD_EXT4_WRITE
which automatically selects CONFIG_EXT4_WRITE if it wasn't defined
already.
Also relevant are the generic filesystem commands, selected by:
CONFIG_CMD_FS_GENERIC
This does not automatically enable EXT4 support for you, you still need
to do that yourself.
Some sample commands to test ext4 support:
1. Check that the commands can be seen in the output of U-Boot help:
UBOOT #help
...
ext4load- load binary file from a Ext4 file system
ext4ls - list files in a directory (default /)
ext4size - determine a file's size
ext4write- create a file in ext4 formatted partition
...
2. To list the files in an ext4-formatted partition, run:
ext4ls <interface> <dev[:part]> [directory]
For example:
UBOOT #ext4ls mmc 0:5 /usr/lib
3. To read and load a file from an ext4-formatted partition to RAM, run:
ext4load <interface> <dev[:part]> [addr] [filename] [bytes]
For example:
UBOOT #ext4load mmc 2:2 0x30007fc0 uImage
4. To write a file to an ext4-formatted partition.
a) First load a file to RAM at a particular address for example 0x30007fc0.
Now execute ext4write command:
ext4write <interface> <dev[:part]> [filename] [Address] [sizebytes]
For example:
UBOOT #ext4write mmc 2:2 /boot/uImage 0x30007fc0 6183120
(here 6183120 is the size of the file to be written)
Note: Absolute path is required for the file to be written
References :
-- ext4 implementation in Linux Kernel
-- Uboot existing ext2 load and ls implementation
-- Journaling block device JBD2 implementation in linux Kernel
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