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Diffstat (limited to 'u-boot/doc/README.commands')
-rw-r--r-- | u-boot/doc/README.commands | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/u-boot/doc/README.commands b/u-boot/doc/README.commands new file mode 100644 index 0000000..d678992 --- /dev/null +++ b/u-boot/doc/README.commands @@ -0,0 +1,31 @@ + +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 = .; |