My Pi2 doesn't cognize One-Wire

Question

I'm using Raspberry Pi 2 with Gentoo.

I tried to use Digital Thermometer(DS18B20) with 1-wire so I prepared:

login as: qwpo1030
Using keyboard-interactive authentication.
Password:
qwpo1030@rpi2-gentoo ~ $ sudo modprobe w1-gpio
Password: qwpo1030@rpi2-gentoo ~ $ sudo modprobe w1-therm 
qwpo1030@rpi2-gentoo ~ $ lsmod
Module                  Size  Used by 
w1_therm                2559  0 
w1_gpio                 3465  0 
wire                   25632  2 w1_gpio,w1_therm 
cn                      4656  1 wire 
ipv6                  335176  18 
binfmt_misc             6418  1 
bcm2708_rng              972  0 
8188eu                818861  0 
uio_pdrv_genirq         2958  0 
uio                     8219  1 uio_pdrv_genirq 
qwpo1030@rpi2-gentoo ~ $ uname -a 
Linux rpi2-gentoo 4.0.5-v7+ #797 SMP PREEMPT Sat Jun 20 02:03:05 BST 2015 armv7l BCM2709 GNU/Linux 
qwpo1030@rpi2-gentoo ~ $ 

But when I type ls /sys/bus/w1/devices It shows nothing:

qwpo1030@rpi2-gentoo ~ $ ls /sys/bus/w1/devices   <-----shows nothing 
qwpo1030@rpi2-gentoo ~ $ 

I really don't know how to resolve this. I tried every solutions I found in google, nothing solves the problem.

Here is my /boot/cmdline.txt

dwc_otg.lpm_enable=0 root=/dev/mmcblk0p3 console=ttyAMA0,38400 
kgdboc=ttyAMA0,38400 console=tty1 rootfstype=ext4 elevator=deadline rootwait usbhid.mousepoll=0 
dtoverlay=w1-gpio,gpiopin=8 dtoverlay=w1-therm,gpiopin=8 bcm2708.w1_gpio_pin=8

※Gentoo uses OpenRC, not systemd.