On Fri, Jul 09, 2021 at 07:13:04AM +0000, Feng Libo wrote:

Uboot implements the simple file protocol of ext4 file system, already. However, the driver is embedded in Uboot. Is it possible to build a standalone ext4 file system driver for UEFI, in the format of efi, just like the helloworld.efi. So I can use the UEFI shell command: load to load the driver and access a ext4 partition.

No, we do not support anything like that. You'll need to look at the other existing UEFI filesystem drivers instead. There's at least one, as of a few years ago.