[Panasonic Let's note CF-SX3] brightness hotkeys don't work by default

[YUKI Hiroshi]

Fn-F1 (brightness down) and Fn-F2 (brightness up) hotkeys don't work by default, on Panasonic Let's note CF-SX3. To activate these hotkeys, I had to do following steps manually:

~~~
$ sudo sed -e 's/(GRUB_CMDLINE_LINUX_DEFAULT="quiet splash)"/\\1 acpi_backlight=vendor acpi_osi="/' -i /etc/default/grub
$ sudo update-grub
~~~

I think these options should be configured by default for Let's note series, not only CF-SX3. I saw another report for CF-RZ4 at:
http://tkyma.hatenablog.jp/entry/2015/10/24/012902 (*Japanese)

I filed this topic here because similar reports seem there:
https://bugs.launchpad.net/ubuntu/+bugs?field.searchtext=hotkey+brightness+&search=Search&field.status%3Alist=NEW&field.status%3Alist=INCOMPLETE_WITH_RESPONSE&field.status%3Alist=INCOMPLETE_WITHOUT_RESPONSE&field.status%3Alist=CONFIRMED&field.status%3Alist=TRIAGED&field.status%3Alist=INPROGRESS&field.status%3Alist=FIXCOMMITTED&field.assignee=&field.bug_reporter=&field.omit_dupes=on&field.has_patch=&field.has_no_package=

If this is wrong place for this topic, please redirect me to correct package.
Thanks!