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