The CSL 300 Mbit/s wifi adapter is available at Amazon and is an inexpensive wifi USB adapter for Linux. It supports 802.11 b/g/n, WPA2, and has an external antenna adapter.
It identifies as follows with “sudo lsusb”:
Bus 003 Device 002: ID 0bda:8172 Realtek Semiconductor Corp. RTL8191SU 802.11n WLAN Adapter
The loaded kernel module is “r8712u” (check with “sudo lsmod | grep r8712u”).
To make it work with Debian Jessie, all you need to do is to install the standard Debian package “firmware-realtek”. The output in “kern.log” after installing the package and plugging in the USB adapter should look something like this:
Sep 27 13:50:37 computername kernel: [ 9.617950] r8712u: module is from the staging directory, the quality is unknown, you have been warned. Sep 27 13:50:37 computername kernel: [ 9.618985] r8712u: Staging version Sep 27 13:50:37 computername kernel: [ 9.619009] r8712u: register rtl8712_netdev_ops to netdev_ops Sep 27 13:50:37 computername kernel: [ 9.619014] usb 4-2: r8712u: USB_SPEED_HIGH with 4 endpoints Sep 27 13:50:37 computername kernel: [ 9.619553] usb 4-2: r8712u: Boot from EFUSE: Autoload OK Sep 27 13:50:37 computername kernel: [ 10.284174] usb 4-2: r8712u: CustomerID = 0x000a Sep 27 13:50:37 computername kernel: [ 10.284178] usb 4-2: r8712u: MAC Address from efuse = 20:ac:3f:b9:b9:b9 Sep 27 13:50:37 computername kernel: [ 10.284181] usb 4-2: r8712u: Loading firmware from "rtlwifi/rtl8712u.bin" Sep 27 13:50:37 computername kernel: [ 10.284258] usbcore: registered new interface driver r8712u Sep 27 13:50:37 computername kernel: [ 10.348992] usb 4-2: firmware: direct-loading firmware rtlwifi/rtl8712u.bin