Add instructions for Realtek adapters

howto/realtek.md

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+## Try this first
+
+If you are facing any problems with Realtek adapters (e.g. Edimax EW-7811Un)
+first try to run create_ap with `-w 2` (i.e. use WPA2 only) or use it
+without passphrase. If you are still facing any problems or you want to
+also use WPA1, then follow the instructions below.
+
+NOTE: The instructions below are only valid for Realtek adapters with 8192 chipset.
+
+## Before installation
+
+If you're using ArchLinux, run:
+
+```
+pacman -S base-devel linux-headers dkms git
+pacman -R hostapd
+```
+
+If you're using Debian, Ubuntu, or any Debian-based distribution, run:
+
+```
+apt-get install build-essential linux-headers-generic dkms git
+apt-get remove hostapd
+apt-get build-dep hostapd
+```
+
+## Install driver
+
+The driver in the mainline of Linux kernel doesn't work well with the 8192 adapters.
+For this reason you need to install the driver that is provided from Realtek. Their
+driver can not be compiled with newer kernels, but since it was an open-source
+release under GPL license some people were able to fixed it and make it compile.
+
+With the following commands you can install a fixed version of Realtek's driver:
+
+```
+git clone https://github.com/pvaret/rtl8192cu-fixes.git
+dkms add rtl8192cu-fixes
+dkms install 8192cu/1.9
+cp rtl8192cu-fixes/blacklist-native-rtl8192.conf /etc/modprobe.d
+cp rtl8192cu-fixes/8192cu-disable-power-management.conf /etc/modprobe.d
+```
+
+After installation, unload the previous driver and load the new one, or just reboot.
+
+## Install hostapd
+
+Realtek's driver is using an old subsystem which is called `wireless-extensions`
+(or `wext`). Hostapd works only with the new subsystem (which is called `nl80211`).
+For this reason Realtek wrote a patch for hostapd. You can install it with the
+following commands:
+
+If you have ArchLinux install [hostapd-rtl871xdrv](https://aur.archlinux.org/packages/hostapd-rtl871xdrv)
+from AUR or just run:
+
+```
+yaourt -S hostapd-rtl871xdrv
+```
+
+If you're using any other distribution, run:
+
+```
+git clone https://github.com/pritambaral/hostapd-rtl871xdrv.git
+wget http://w1.fi/releases/hostapd-2.2.tar.gz
+tar zxvf hostapd-2.2.tar.gz
+cd hostapd-2.2
+patch -p1 -i ../hostapd-rtl871xdrv/rtlxdrv.patch
+cp ../hostapd-rtl871xdrv/driver_* src/drivers
+cd hostapd
+cp defconfig .config
+echo CONFIG_DRIVER_RTW=y >> .config
+make
+make install
+```