README.commands 1.1 KB

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  1. Commands are added to U-Boot by creating a new command structure.
  2. This is done by first including command.h
  3. Then using the U_BOOT_CMD() macro to fill in a cmd_tbl_t struct.
  4. U_BOOT_CMD(name,maxargs,repeatable,command,"usage","help")
  5. name: is the name of the commad. THIS IS NOT a string.
  6. maxargs: the maximumn numbers of arguments this function takes
  7. command: Function pointer (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
  8. usage: Short description. This is a string
  9. help: long description. This is a string
  10. **** Behinde the scene ******
  11. The structure created is named with a special prefix (__u_boot_cmd_)
  12. and placed by the linker in a special section.
  13. This makes it possible for the final link to extract all commands
  14. compiled into any object code and construct a static array so the
  15. command can be found in an array starting at __u_boot_cmd_start.
  16. If a new board is defined do not forget to define the command section
  17. by writing in u-boot.lds ($(TOPDIR)/board/boardname/u-boot.lds) these
  18. 3 lines:
  19. __u_boot_cmd_start = .;
  20. .u_boot_cmd : { *(.u_boot_cmd) }
  21. __u_boot_cmd_end = .;