blob: 9eb367104fd9a1bc77ede04bc11c1ead51b602b9 [file] [log] [blame]
wdenk0d498392003-07-01 21:06:45 +00001
2Commands are added to U-Boot by creating a new command structure.
Peter Meerwald00309c62012-02-08 05:31:52 +00003This is done by first including command.h, then using the U_BOOT_CMD() macro
4to fill in a cmd_tbl_t struct.
wdenk0d498392003-07-01 21:06:45 +00005
6U_BOOT_CMD(name,maxargs,repeatable,command,"usage","help")
7
8name: is the name of the commad. THIS IS NOT a string.
Peter Meerwald00309c62012-02-08 05:31:52 +00009maxargs: the maximum number of arguments this function takes
10repeatable: either 0 or 1 to indicate if autorepeat is allowed
wdenk0d498392003-07-01 21:06:45 +000011command: Function pointer (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
12usage: Short description. This is a string
Peter Meerwald00309c62012-02-08 05:31:52 +000013help: Long description. This is a string
wdenk0d498392003-07-01 21:06:45 +000014
15
Peter Meerwald00309c62012-02-08 05:31:52 +000016**** Behind the scene ******
wdenk0d498392003-07-01 21:06:45 +000017
Albert ARIBAUDef123c52013-02-25 00:59:00 +000018The structure created is named with a special prefix and placed by
19the linker in a special section using the linker lists mechanism
20(see include/linker_lists.h)
wdenk0d498392003-07-01 21:06:45 +000021
22This makes it possible for the final link to extract all commands
23compiled into any object code and construct a static array so the
Albert ARIBAUDef123c52013-02-25 00:59:00 +000024command array can be iterated over using the linker lists macros.
wdenk0d498392003-07-01 21:06:45 +000025
Albert ARIBAUDef123c52013-02-25 00:59:00 +000026The linker lists feature ensures that the linker does not discard
27these symbols when linking full U-Boot even though they are not
28referenced in the source code as such.
Tom Rini2d1d6582012-09-20 06:02:43 +000029
wdenk0d498392003-07-01 21:06:45 +000030If a new board is defined do not forget to define the command section
31by writing in u-boot.lds ($(TOPDIR)/board/boardname/u-boot.lds) these
323 lines:
33
Marek Vasut6c7c9462012-10-12 10:27:04 +000034 .u_boot_list : {
Albert ARIBAUDef123c52013-02-25 00:59:00 +000035 KEEP(*(SORT(.u_boot_list*)));
Marek Vasut6c7c9462012-10-12 10:27:04 +000036 }