Comment 5 for bug 875893

I was not able to open an upstream bug at bugzilla.kernel.org because
it is still offline.

It turns out that this laptop requires the 'samsung-laptop' platform
driver in order for backlight control to work. The driver contains a
whitelist of the DMI strings of models known to require this driver.
This laptop identifies itself thusly:

$ sudo dmidecode -s system-product-name
 N150P

The attached patch adds this model to the whitelist which causes the
driver to load and work as expected. The boot parameter
"acpi_backlight=vendor" seems to have the same ultimate affect as this
patch but needs to be manually set.

I have forwarded the patch upstream:
https://lkml.org/lkml/2011/12/22/364
and
http://thread.gmane.org/gmane.linux.drivers.platform.x86.devel/2808