Latest working kernel version:
 2.6.24
Earliest failing kernel version:
 2.6.25
Distribution:
 Debian SID
Hardware Environment:
 Yakumo QuickWLAN USB (ZyDAS)
Software Environment:
 wpa_supplicant
Problem Description:
 I use a USB wireless adapter : Yakumo uickWLAN USB 2.0, with a ZyDAS
chipset, zd1211.
I use it with a WPA AP, running with OpenWRT on a Lynksys wrt54GS.

It works with the kernels from 2.6.18 to 2.6.24.
It does not initialise, nor scan with 2.6.25.
I saw thiat this driver (zd1211rw) has changed to the more generic
mac80211 layer from Deviscape.

The symptome is : the link LED stays off, wpa_supplicant cannot initiate
scan, and there is no network connection.

filename:
/lib/modules/2.6.25-2-686/kernel/drivers/net/wireless/zd1211rw/zd1211rw.ko
version:        1.0
author:         Daniel Drake
author:         Ulrich Kunitz
description:    USB driver for devices with the ZD1211 chip.
license:        GPL
srcversion:     D9B25B58E2203D71BECF7BE
alias: [... lots of aliases ...]
depends:        mac80211,usbcore,firmware_class
vermagic:       2.6.25-2-686 SMP mod_unload 686

The difference in 2.6.24 wich works is :
filename:
/lib/modules/2.6.24-1-686/kernel/drivers/net/wireless/zd1211rw/zd1211rw.ko
version:        1.0
author:         Daniel Drake
author:         Ulrich Kunitz
description:    USB driver for devices with the ZD1211 chip.
license:        GPL
srcversion:     7D1B5B65930FED9BD9BA337
alias: [... lots of aliases ...]
depends:        mac80211,usbcore,firmware_class
depends:        usbcore,ieee80211softmac,ieee80211,firmware_class
vermagic:       2.6.24-1-686 SMP mod_unload 686

The initialisation logs in kern.log :
- With 2.6.25 :
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: no suspend for driver
zd1211rw?
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: zd_chip_control_leds
error -113
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: zd_chip_control_leds
error -113
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: zd_chip_control_leds
error -108
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: zd_chip_control_leds
error -113
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: error ioread32(CR_REG1):
-22
May 15 21:19:07 basse kernel: zd1211rw 3-2:1.0: eth0
May 15 21:19:18 basse kernel: zd1211rw 3-2:1.0: firmware version 4605
May 15 21:19:18 basse kernel: zd1211rw 3-2:1.0: zd1211 chip 0b3b:1630
v4330 high 00-01-36 RF2959_RF pa0 -----

- With 2.6.24 :
interface driver zd1211rw
May 15 21:46:39 basse kernel: zd1211rw 3-2:1.0: eth0
May 15 21:46:39 basse kernel: usbcore: registered new interface driver
zd1211rw
May 15 21:46:39 basse kernel: zd1211rw 3-2:1.0: firmware version 4605
May 15 21:46:39 basse kernel: zd1211rw 3-2:1.0: zd1211 chip 0b3b:1630
v4330 high 00-01-36 RF2959_RF pa0

One more log, the one from wpa_suplicant :
several time this line :
Failed to initiate AP scan.

Steps to reproduce:
 Use a ZyDAS USB Wireless adapter with kernel-2.6.25.