AP mode (via hostapd) support for wifi chips that identify themselves as RTL8188CUS (or variants thereof). If you've seen or heard someone claim that a certain wifi chip works with a special version of hostapd driver called rtl871xdrv, this is it.
This is not the full hostapd source however. These are just patches and extra code to compile rtl871xdrv with a fresh hostapd source.
Wifi chips like RT8188C and RT8192C, recognized as RTL8188CUS (or variants thereof) do not support the standard nl80211 driver of hostapd. Their in-kernel drivers are also buggy and not very featureful. Realtek released their drivers for such chips under the GPL, but never bothered to update them. But I guess a one-time code dump is better than no source code at all.
Realtek's code dump contained a kernel driver and a special driver for hostapd. (What is this? 2005?) As of writing, the kernel driver is being maintained for modern kernels at dz0ny/rt8192cu.
The hostapd driver however, wasn't provided as a driver. A modified hostapd, somewhere in its 0.8.x version, was dumped. If you wanted a newer hostapd, well, too bad.
This repo has the extracted modifications to mainline hostapd done by Realtek, adapted for hostapd 2.2. It is very likely that these would work with hostapd 2.x.
Get a fresh copy of hostapd from http://hostap.epitest.fi/hostapd/ or through your distro's methods.
Inside the directory that contains hostapd, src, wpa_supplicant, apply the patch:
$ patch -Np1 -i </path/to/rtl871xdrv.patch>
Copy the driver_rtl.h and driver_rtw.c files into src/drivers/
Copy the .config file to hostapd/.config. You may try editting and augmenting .config with other options, but bear in mind that nothing other than the provided settings in .config (provided by Realtek, they are) have been tested.
Now you're all set to compile. Use your distro's build system, if set up, to compile and package and everything.
For simple compiling: change into the hostapd directory, the same one you just copied .config into, and run make.
If make succeeds, you'll have two binaries in the same directory: hostapd and hostapd_cli. The former is the actual AP daemon, the latter is just a helper for controlling a running daemon.
A simple hostapd.conf file has been provided.
No code here has been written by me, only existing code from Realtek has been modified. As per the original license:
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2 as
published by the Free Software Foundation.
Alternatively, this software may be distributed under the terms of BSD
license.