One more thing respectively to my previous comment:
$ acpi_listen
# single brightness down button pressed (Fn+F2)
video DD02 00000087 00000000
video DD02 00000087 00000000
# single brightness up button pressed (Fn+F3)
video DD02 00000086 00000000
video DD02 00000086 00000000
One more thing respectively to my previous comment:
$ acpi_listen
# single brightness down button pressed (Fn+F2)
video DD02 00000087 00000000
video DD02 00000087 00000000
# single brightness up button pressed (Fn+F3)
video DD02 00000086 00000000
video DD02 00000086 00000000