the acpi_call is not for switching the GPU, but for shutdown the nvidia card.
To do that clone the repository and simply execute in terminal :
$ git clone https://github.com/peberlein/acpi_call.git
$ cd acpi_call
$ sudo insmod acpi_call.ko
$ sudo ./asus1215n.sh off
this shutdown save the power of the battery. To shutdown the nvidia card at every time :
$ cd ..
$ sudo cp -rf ./acpi_call /opt/
$ sudo echo "insmod /opt/acpi_call/acpi_call.ko
> /opt/asus1215n.sh off" >> /etc/rc.local
Now a day, you can't use the nvidia card on linux because the driver don't exist... Why? I don't know....
but I hope nVidia work on it...