1U-Boot supports access of both ext2 and ext4 filesystems, either in read-only 2mode or in read-write mode. 3 4First, to enable support for both ext4 (and, automatically, ext2 as well), 5but without selecting the corresponding commands, enable one of the following: 6 7 CONFIG_FS_EXT4 (for read-only) 8 CONFIG_EXT4_WRITE (for read-write) 9 10Next, to select the ext2-related commands: 11 12 * ext2ls 13 * ext2load 14 15or ext4-related commands: 16 17 * ext4size 18 * ext4ls 19 * ext4load 20 21use one or both of: 22 23 CONFIG_CMD_EXT2 24 CONFIG_CMD_EXT4 25 26Selecting either of the above automatically selects CONFIG_FS_EXT4 if it 27wasn't enabled already. 28 29In addition, to get the write access command "ext4write", enable: 30 31 CONFIG_CMD_EXT4_WRITE 32 33which automatically selects CONFIG_EXT4_WRITE if it wasn't defined 34already. 35 36Also relevant are the generic filesystem commands, selected by: 37 38 CONFIG_CMD_FS_GENERIC 39 40This does not automatically enable EXT4 support for you, you still need 41to do that yourself. 42 43Some sample commands to test ext4 support: 44 451. Check that the commands can be seen in the output of U-Boot help: 46 47 UBOOT #help 48 ... 49 ext4load- load binary file from a Ext4 file system 50 ext4ls - list files in a directory (default /) 51 ext4size - determine a file's size 52 ext4write- create a file in ext4 formatted partition 53 ... 54 552. To list the files in an ext4-formatted partition, run: 56 57 ext4ls <interface> <dev[:part]> [directory] 58 59 For example: 60 UBOOT #ext4ls mmc 0:5 /usr/lib 61 623. To read and load a file from an ext4-formatted partition to RAM, run: 63 64 ext4load <interface> <dev[:part]> [addr] [filename] [bytes] 65 66 For example: 67 UBOOT #ext4load mmc 2:2 0x30007fc0 uImage 68 694. To write a file to an ext4-formatted partition. 70 71 a) First load a file to RAM at a particular address for example 0x30007fc0. 72 Now execute ext4write command: 73 ext4write <interface> <dev[:part]> [filename] [Address] [sizebytes] 74 75 For example: 76 UBOOT #ext4write mmc 2:2 /boot/uImage 0x30007fc0 6183120 77 (here 6183120 is the size of the file to be written) 78 Note: Absolute path is required for the file to be written 79 80References : 81 -- ext4 implementation in Linux Kernel 82 -- Uboot existing ext2 load and ls implementation 83 -- Journaling block device JBD2 implementation in linux Kernel 84