Added README

Taken from https://github.com/Lekensteyn/acpi-stuff

README.md

@@ -0,0 +1,55 @@
+*Migrated from https://github.com/Lekensteyn/acpi-stuff*
+
+bbswitch is a kernel module which automatically detects the required ACPI calls
+for two kinds of Optimus laptops. It has been verified to work with "real"
+Optimus and "legacy" Optimus laptops (at least, that is how I call them). The
+machines on which these tests has performed are:
+
+- Clevo B7130 - GT 425M ("real" Optimus, Lekensteyns laptop)
+- Dell Vostro 3500 - GT 310M ("legacy" Optimus, Samsagax' laptop)
+
+(note: there is no need to add more supported laptops here as the universal
+calls should work for every laptop model supporting either Optimus calls)
+
+It's preferred over manually hacking with the acpi_call module because it can
+detect the correct handle preceding _DSM and has some built-in safeguards:
+
+- You're not allowed to disable a card if a driver (nouveau, nvidia) is loaded.
+- Before suspend, the card is automatically enabled. When resuming, it's
+  disabled again if that was the case before suspending. Hibernation should
+  work, but it not tested.
+
+To use it, build the module first (kernel headers are required):
+
+    make
+Then load it (requires root privileges, i.e. `sudo`):
+
+    make load
+If your card is supported, there should be no error. Otherwise, you get a "No
+such device" (ENODEV) error. Check your kernel log (dmesg) for more
+information.
+
+Usage (`#` means "run with root privileges, i.e. run it prefixed with `sudo `):
+
+Get the status:
+
+    # cat /proc/acpi/bbswitch  
+    0000:01:00.0 ON
+
+Turn the card off, respectively on:
+
+    # tee /proc/acpi/bbswitch <<<OFF
+    # tee /proc/acpi/bbswitch <<<ON
+If the card stays on when trying to disable it, you've probably forgotten to
+unload the driver,
+
+    $ dmesg |tail -1
+    bbswitch: device 0000:01:00.0 is in use by driver 'nouveau', refusing OFF
+This module has been integrated in Bumblebee "Tumbleweed". Please report any
+issues on this module in the issue tracker and provide the following details:
+
+- The output of `dmesg | grep -C 10 bbswitch:`
+- The kernel version `uname -a`
+- Your distribution and version (if applicable)
+- The output of `lspci -d10de: -vvv`
+- The version of your Xorg and the driver