Genkernel variable to specify crypt key device

[noqrax]

Hello, I'm trying to boot my encrypted rood drive, and it is almost done (actually system successfully mounts root device).

It is encrypted with luks (default settings), and contains lvm. To unlock root device I use initramfs made by genkernel with --lvm --luks flags.

I already specified crypt_root, root_key and real_root variables in grub.
When it boots, it scans all possible media to find specified key. But there is "root key device()" function in genkernel, it can be seen during the boot, if crypt_root points to device that not present in system. In that case you are able to manually specify roo, root key and root key device.
So how to set root key device in grub (variable name), and where it have to be put.
Maybe root_key was not specified properly i did it so: root_key=/key (may be there is way to specify both by same variable, e.g. root_key=/dev/sdd:/key).
My current order is: crypt_root root_key dolvm real_root.

Also after I've configured that, dmcrypt init script just skips to unlock my home partition. It uses luks by passphrase and must be unlocked at boot runlevel. Previously it worked fine.