The Zydas chipset is a new WLAN single chip solution for 802.11a/b/g wireless networks with USB2.0 and 16bit interface.
By coincidence I got the chance to test this chipset in a new Longshine combined Bluetooth + WLAN dongle, the Longshine LCS-8170. To make it brief, it works perfectly well!
The device contains a built-in USB2.0 HUB and two USB2.0 devices, the Zydas WLAN and the Bluetooth USB-HCI chipset. The Bluetooth part works right out of the box using the standard kernel built-in BlueZ HCI-USB driver.
The Zydas ZD1211 WLAN requires a seperate driver which can be found on Sourceforge, see the links below. The driver is for 2.4x and 2.6.x kernels. Installation is pretty straight forward. Simply download the driver, unpack the source, issue "make" and then "make install" - do this as root, as it is usual for kernel modules. You should have compiled your running kernel yourself and have the corresponding source tree still installed.
After installation it was plug and play, simply plug in the dongle and you will get a new network interface "wlan". The wireless extensions of the device will only become available and visible after the network interface is up'ped.
This article is still valid for older kernels. There is a Zydas driver in mainline kernel releases starting from 2.6.18-rc1.