After a fresh Ubuntu install on my laptop, I discovered the function keys for screen brightness control (Fn+F4 and Fn+F5) are not working. Digging around here, I managed to get it to work by following the solution suggested on this post and that one, but alas — after applying it, a strange problem occurred:

Setting the brightness level to any value other than minimum or maximum, the screen starts flickering back and forth from the selected level to full brightness, apparently due to Dell's power saver attempting to dim the screen to adjust the brightness levels.

I looked up for a solution here on the site, and possibly everywhere, with no avail. Also tried:

• To manually control the brightness by configuring the ACPI level (setting values by echo [some_value] | sudo tee /sys/class/backlight/[vendor]_backlight/[some_key], without success.
• Installing the Intel graphics driver, thinking it's missing. Realized it's installed out of the box by installing Mesa Utils.

How to resolve this?

Environment

• Model: Dell Studio XPS 13
• OS: Windows 7 64bit / Ubuntu 12.04 32bit (dual boot)
• Graphics Driver: Intel HD 3000 (Sandybridge Mobile x86/MMX/SSE2)

• lshw -C display output:

  *-display               
       description: VGA compatible controller
       product: 2nd Generation Core Processor Family Integrated Graphics Controller
       vendor: Intel Corporation
       physical id: 2
       bus info: pci@0000:00:02.0
       version: 09
       width: 64 bits
       clock: 33MHz
       capabilities: msi pm vga_controller bus_master cap_list rom
       configuration: driver=i915 latency=0
       resources: irq:47 memory:f0000000-f03fffff memory:e0000000-efffffff ioport:2000(size=64)