| |
| 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 maximumn numbers of arguments this function takes |
| 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 |
| |
| |
| **** Behinde the scene ****** |
| |
| The structure created is named with a special prefix (__u_boot_cmd_) |
| and placed by the linker in a special section. |
| |
| 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 can be found in an array starting at __u_boot_cmd_start. |
| |
| 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_cmd_start = .; |
| .u_boot_cmd : { *(.u_boot_cmd) } |
| __u_boot_cmd_end = .; |
