ZD1211 wireless hacking
I’ve been spending some time over the last few weeks hacking on a USB Wireless-LAN adapter based on the ZyDAS ZD1211 chip. There are actually 40+ ZD1211-based products available on the market so Linux support for this device has some big implications.
ZyDAS themselves produce a Linux driver which is updated semi-regularly, however the code is horrible and the driver is unreliable for many. On the other hand, it’s good that they have released a full GPL driver and have also been cooperative with providing technical documentation and flexibility on redistributing the firmware. There have been some forks which try to stabilise the vendor driver, the latest being zd1211.ath.cx, but none of these forks have been aiming for kernel inclusion.
In January, myself and Danny van Dyk started a driver rewrite project and published some initial code. Soon after doing so, I was contacted by Ulrich Kunitz, a hacker who had spent several weeks previously developing a rewritten driver. We switched over to Ulrich’s driver base and continued from there.
Unlike the vendor driver, we are taking full advantage of Linux’s IEEE 802.11 wireless stack. As the driver must do most things in software, we are also using the softmac extension which simplifies many generic operations (scanning, authentication, etc). A nice side effect of this is that when we have written the code to send and receive packets, the driver is almost complete (the other layers do the rest of the work).
Yesterday, I hacked together an initial scanning implementation and successfully scanned my local area for wireless networks. This means that receiving packets is more-or-less working – a nice milestone to reach.
Some information and links to the code can be found here. Be warned, this is useful for users yet. Watch this space for updates.