Updating BIOS with USB stick on Thinkpad (Linux)

Basically Lenovo supports two ways of upgrading BIOS: Windows upgrade utility or burning ISO to CD.
I don't have nor Windows nor CD-ROM on my laptop.

Idea is to prepare bootable USB stick from the ISO.

1) Get the BIOS Update Bootable CD from http://support.lenovo.com (In my case for T530)
2) Convert ISO to img. This is most important step because. Based on manual from thinkwiki.org i'd used
"geteltorito" script for convertation. This script supports special harddisk emulation (BootMediaType=4) ISO format.

wget http://userpages.uni-koblenz.de/~krienke/ftp/noarch/geteltorito/geteltorito
chmod +x geteltorito
./geteltorito -o bios.img ~/Downloads/g4uj25us.iso

3) dd image onto USB stick. ( CAREFUL: Use real path to USB instead of /dev/sdX )

sudo dd if=bios.img of=/dev/sdX bs=512K

4) Boot from USB and follow the instructions. Also please read official readme before doing any flashing. (i.e. for T530)

NOTES:
- Make sure USB booting enabled in BIOS. "Config --> USB --> USB UEFI BIOS support" should be "Enabled"
- After updating firmware i've plunged into issue with not workable "brightness control" keys. Solution: add kernel paramenter acpi_osi="!Windows 2012"