I got an Edimax EW-7811Un USB nano wireless adapter in order to add a short-range AP to a Pi2. The thing says 'Ideal for Raspberry Pi' on the tin..
When I put it in, it was recognized ok but I could not get hostapd to work with it. Then I found a version of hostapd that would work, but the AP would die overnight (adapter reversed to STA mode, hostapd process gone.) Finally I have found a setup that seems solid. For anyone's interested, here is my recipe.
Before that I'd like to point I don't think this is the greatest adapter to choose as an AP. First off it doesn't work with the stock hostapd software, then it does not support any form of best channel selection (the 'iwlist wlan0 scan ; cat /proc/net/rtl819xD/wlan0/best_channel' method advertised in Realtek's docs no longer works) nor on-the fly channel change, it is limited to 8 clients, and of course it is 2.4GHz only and its range is limited.
But I got it to run reliably at wifi-N speeds (my mac mini desktop client topped at 73Mbps), it is tiny and cheap. Not so bad overall.
Now for the recipe:
a) Machine id and software versions (a Pi2 Model B with current firmware and raspbian, managed by systemd). As a precaution, I've set max_usb_current=1 in the Pi boot parameters, but given the requirement of 500mA for the device and the fact the hub won't be further populated, I don't really think this is necessary in my case. Ran fine without it, feeding the Pi with either a 5W or a 12W PSU.b) The Edimax adapter plugged into the Pi, using the stock 8192cu module and all-important module options:c) Version of hostapd used: a debianified, Realtek-specific version of hostapd 2.4 (jessie offers v. 2.3) available on github at https://github.com/jekader/hostapd-rtl.
To build you'll need the raspbian kernel source code, or kernel headers.
For some reason raspbian.org does not offer kernel-related packages, but with a bit of luck I found at https://www.niksula.hut.fi/~mhiienka/Rpi/linux-headers-rpi/ a linux-headers-4.1.15-v7+_4.1.15-v7+-2_armhf.deb package already made by a kind soul (a bit of digging reveals this is thanks to Markus Hiienkari, a graduate of Aalto University in Finland)
Following Jeka Der's instructions and making sure you compile with gcc version 4.9, you'll end up with an hostapd-rtl package in no time.d) Finally, relevant items in my hostapd.conf (the hostapd-rtl package includes a demo file)Where 'Realtek's docs' are referenced, this means the documentation in the driver source archive you can recover from Realtek downloads area. The file I downloaded was named 'RTL8188C_8192C_USB_linux_v4.0.2_9000.20130911.zip '.
HTH, EOF