Commands are added to U-Boot by creating a new command structure. This is done by first including command.h, then using the U_BOOT_CMD() macro to fill in a cmd_tbl_t struct. U_BOOT_CMD(name,maxargs,repeatable,command,"usage","help") name: is the name of the commad. THIS IS NOT a string. maxargs: the maximum number of arguments this function takes repeatable: either 0 or 1 to indicate if autorepeat is allowed command: Function pointer (*cmd)(struct cmd_tbl_s *, int, int, char *[]); usage: Short description. This is a string help: Long description. This is a string **** Behind the scene ****** The structure created is named with a special prefix and placed by the linker in a special section using the linker lists mechanism (see include/linker_lists.h) This makes it possible for the final link to extract all commands compiled into any object code and construct a static array so the command array can be iterated over using the linker lists macros. The linker lists feature ensures that the linker does not discard these symbols when linking full U-Boot even though they are not referenced in the source code as such. If a new board is defined do not forget to define the command section by writing in u-boot.lds ($(TOPDIR)/board/boardname/u-boot.lds) these 3 lines: .u_boot_list : { KEEP(*(SORT(.u_boot_list*))); }