using sysctl.conf for module that initialize in early bootup

Dear All, I am trying to introduce a flag which controls probe of a driver that initialize in device_initcall(). I want to use a flag, if the flag is true driver will be initialed and if its false then probe will return without registering the driver. The value of flag can be changed at runtime and that should persist after reboot. I have searched and found about using /etc/sysctl.conf for this purpose. I observed that /etc is not mounted on system when device_initcall() executes. is there any other way by which i can implement this feature? Thanks & Regards, *Pankaj Gupta*