Archive for May, 2007

ZD1211 back in production

Thursday, May 24th, 2007

Since the Atheros acquisition, introduction of new ZyDAS ZD1211 USB-wireless devices has been concerningly slow.

Fortunately, some new ZD1211 devices have been popping up recently, based on new radio chips. After some help from the community, I managed to get my hands on the new types and write zd1211rw code needed to support these chips.

The first new chip, the AL2230S, only needed a few changes on top of the older AL2230 code. This radio is working well.

The second new chip is especially interesting: the Ubec UW2453. Ubec publish full technical specs for this chip, so we’re able to understand more than usual about the ZD1211 interactions with the radio. Maybe due to it’s complexity, the UW2453 isn’t performing quite as well as the other radios, but this should improve after time. I emailed ZyDAS some feedback about their UW2453 programming code – I think I spotted a few mistakes.

Third, we started seeing the already-supported AL7230B RF chip being combined with the ZD1211B base chip on some newer ZyXEL products. This particular combination was not supported before, but thanks to some testers on the mailing lists, the code has been written and submitted to support these.

Fourth, Atheros appear to have rebranded the ZD1211B chip as AR5007UG. These devices are appearing in Medion laptops, very popular in some parts of Europe. The first ones seem to be based on the UW2453 RF mentioned above. I’m especially interested to hear from people who have AR5007UG devices in other laptops or in standalone USB-dongle form, and also if they exist based on other RF chips.

All the above will be available in Linux 2.6.22, except UW2453/AR5007UG which will be available in 2.6.23.

On a final note, I moved the zd1211rw homepage to the new linuxwireless.org wiki. One nice feature here is that the zd1211rw supported devices list gets aggregated onto the more general Linux-supported USB wireless devices list, however we’re the only USB driver with device information published there at the moment.

Dell laptop LCDs not powering up on lid open event

Monday, May 7th, 2007

My Dell Inspiron 640m laptop has some strange behaviour which irritates me: when the lid is closed, the display turns off as you might expect. However, when the lid is opened, the display remains off.

The workaround up to this point has been to use acpid to listen for “lid open” events, and then have an event handler which uses vbetool (or xset) to restore power to the display.

I’ve been digging deeper into this problem, and have realised that the above behaviour is entirely due to the behaviour coded into the system ACPI tables (DSDT). With just a few lines of code, this strange behaviour can be “corrected”.

I’ve posted a DSDT patch to fix this. To use it, you have to decompile your DSDT, apply the patch, recompile it, and then build it into your kernel. For interested people, there are plenty of DSDT-patching guides on the Gentoo Forums and similar.

After applying this fix, I can uninstall acpid completely and the screen blank/unblank “just works”. The above patch is suitable for Dell 640m and e1405 models, and possibly others too.

UPDATE: I’m working on kernel patches which will mean that no DSDT hacking is needed, and LCD resuming will really “just work”. Keep an eye on my weblog for more.