Comment 34 for bug 321578

Also affects the Toshiba Satellite L350-235 on Ubuntu 11.04
The following workaround solved both the non-functional fn+F6/F7 Display brightness keys and the auto-dim when going onto battery power, and seems to have solved the fan-always-on problem too:

1. Install lm-sensors: sudo apt-get install lm-sensors
2. Run sensors-detect which will install the 'coretemp' module:
$ more /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.

lp
rtc

# Generated by sensors-detect on Tue May 10 21:00:51 2011
# Chip drivers
coretemp

$ sensors
acpitz-virtual-0
Adapter: Virtual device
temp1: +53.0°C (crit = +114.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Core 0: +50.0°C (high = +105.0°C, crit = +105.0°C)

coretemp-isa-0001
Adapter: ISA adapter
Core 1: +46.0°C (high = +105.0°C, crit = +105.0°C)

3. Modify /etc/default/grub:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux"

4. Update grub: sudo update-grub

5. Reboot your machine

NOTE: The toshiba_acpi.ko kernel module will NOT load for this laptop either, but it is not required.