xref: /openbmc/u-boot/doc/README.commands (revision 6751b05f)
1
2Commands are added to U-Boot by creating a new command structure.
3This is done by first including command.h, then using the U_BOOT_CMD() macro
4to fill in a cmd_tbl_t struct.
5
6U_BOOT_CMD(name,maxargs,repeatable,command,"usage","help")
7
8name:	 is the name of the commad. THIS IS NOT a string.
9maxargs: the maximum number of arguments this function takes
10repeatable: either 0 or 1 to indicate if autorepeat is allowed
11command: Function pointer (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
12usage:	 Short description. This is a string
13help:	 Long description. This is a string
14
15
16**** Behind the scene ******
17
18The structure created is named with a special prefix (__u_boot_cmd_)
19and placed by the linker in a special section.
20
21This makes it possible for the final link to extract all commands
22compiled into any object code and construct a static array so the
23command can be found in an array starting at __u_boot_cmd_start.
24
25If a new board is defined do not forget to define the command section
26by writing in u-boot.lds ($(TOPDIR)/board/boardname/u-boot.lds) these
273 lines:
28
29	__u_boot_cmd_start = .;
30	.u_boot_cmd : { *(.u_boot_cmd) }
31	__u_boot_cmd_end = .;
32