Hello. I wrote a patch to add sendkey functionality to grub2. After
loading sendkey module some new environments variables appear with which
one may control the sequence of keys that would be sent to OS or next
bootloader. This functionality is useful in different cases. One example
 is entering "safe mode" in some OS when without this feature you
desperately try many times to press "magic key" in exactly good moment.
Another usage example is chainloading another bootloader. Then you can
send someting like "down down enter" to it and avoid another delay. The
implementation as environment variables has its downside as I don't know
where to put help about it. Perhaps possibility of adding help notice to
environment variables would be a good idea. Then we could do like
>help root
root is a variable containing root device.
For implementing this functionality I needed my function to be executed
right before booting. To do it I added a simple interface for adding
"preboot" functions:
struct grub_preboot_t *grub_loader_add_preboot (grub_err_t
(*preboot_func) (int));
As parameter this function recieves a callback (integer parameter to
callback is noreturn variable). This function returns a handle with
which the preboot function may be removed using
void grub_loader_remove_preboot (struct grub_preboot_t *p);
Implementation uses linked lists and tries to implement it in as few
commands as possible since this code is a part of core image. This
interface can later be reused for adding different hooks to bios ("map",
"memdisk",...). Now the questions are:
Whether such interface is OK for grub2?
Whether we need also interface for adding "postboot" commands? (in case
boot_function returns)
Variables made available after loading sendkey module:
sendkey - a space-separated list of keys to be sent
kb_num, kb_caps, kb_scroll, kb_insert, kb_wait - [keep|on|off] - set
numlock, capslock, scrollock, insert or wait state
kb_noled - [0|1] When set to 1 the LED state is not changed to match
num-/caps-/scrolllock state
"kb_lshift", "kb_rshift", "kb_sysreq", "kb_numkey", "kb_capskey",
"kb_scrollkey", "kb_insertkey", "kb_lalt", "kb_ralt", "kb_lctrl",
"kb_rctrl" - [keep|on|off] When set to on emulate pressing and holding
of corresponding key. To undo just press the corresponding key on your
keyboard

Regards
Vladimir Serbinenko