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, use one of:
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#define CONFIG_FS_EXT4 (for read-only)
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#define 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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#define CONFIG_CMD_EXT2
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#define CONFIG_CMD_EXT4
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Selecting either of the above automatically defines CONFIG_FS_EXT4 if it
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wasn't defined already.
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In addition, to get the write access command "ext4write", use:
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#define CONFIG_CMD_EXT4_WRITE
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which automatically defines 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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#define 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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