Support for Realtek 802.11n USB devices

Damien Bergamini (damien@) submitted an article on his latest work on wireless networking devices. He recently committed rsu(4), below is the commit message and some background behind it:

CVSROOT:        /cvs
Module name:        src
Changes by:        damien@cvs.openbsd.org        2010/12/11 13:48:21

Modified files:
        share/man/man4 : usb.4 Makefile
        sys/dev/usb    : files.usb
        sys/arch/i386/conf: GENERIC
        sys/arch/amd64/conf: GENERIC
Added files:
        share/man/man4 : rsu.4
        sys/dev/usb    : if_rsu.c if_rsureg.h

Log message:
rsu(4), a driver for Realtek RTL8188SU, RTL8191SU and RTL8192SU
802.11n USB devices.
These are FullMAC devices that require a firmware to operate;
see man page for details.

Great thanks to Brad for donating hardware.
Committed over the TRENDnet TEW-649UB.

ok deraadt@

With this commit and the recent commit of urtwn(4), OpenBSD -current now has support for all the single-chip 802.11n USB devices from Realtek. With the run(4) and otus(4) drivers already in 4.8, OpenBSD supports a large amount of the 802.11n USB devices available in stores. One notable exception is the AR9271 chip from Atheros which is not yet supported, but this is being worked on.

From left to right, the gigantic Netgear WNDA3100 (Atheros AR9170) supported by the otus(4) driver, the D-Link DWA-131 A1 (Realtek RTL8191SU) and the ASUS USB N-10 (Realtek RTL8192SU) both supported by the rsu(4) driver and the tiny Hercules HWNUp-150 (Realtek RTL8188CU) supported by the urtwn(4) driver.

It is amazing the efforts that have been made to reduce the size of the 802.11 USB adapters. The RTL8188CU is roughly the size of a Bluetooth adapter or a dongle for a wireless keyboard. The WNDA3100 looks ridiculously huge in comparison, granted it is a dual-band device while the others are 2.4GHz only, but still.

The D-Link DWA-131 A1 and the Netgear WNDA3100 stripped of their plastic cases. Despite its small size, the D-Link has two U.FL connectors. We can also see that the Atheros AR9170 is definitely not single-chip. It has two U.FL connectors too, the second is on the other side of the card, not visible here.

The rsu(4) and urtwn(4) drivers are very different. The RTL8188SU, RTL8191SU and RTL8192SU are FullMAC devices. They handle many parts of the 802.11 MLME in firmware. The driver communicates with the firmware through high-level commands. The firmware that is loaded in the devices and that is available as a binary package is rather big (122KB) as a consequence.
The RTL8188CU and RTL8192CU devices are SoftMAC devices, leaving most of the work to the driver. They need a firmware too, but it is much more lightweight (16KB).

The rsu(4) and urtwn(4) drivers currently support the devices in legacy 802.11b/g modes only, but I am getting very close to support 802.11n, at least for the RX path.

This is the list of devices that should work with either the rsu(4) driver:

• ASUS USB-N10
• D-Link DWA-131 A1
• Hercules HWGUn-54
• Hercules HWNUm-300
• Planex GW-USNano
• Sitecom WL-349 v1
• Sitecom WL-353
• TRENDnet TEW-648UB
• TRENDnet TEW-649UB

• Airlink101 AWLL5088
• Aus. Linx AL-9604R1S
• B-Link BL-LW05-5R
• Belkin F7D1102
• D-Link DWA-133
• Digitus DN-7042
• Edimax EW-7811Un
• EDUP EP-N8508
• Full River FR-W100NUL
• Hercules HWNUp-150
• Planex GW-USEco300
• Planex GW-USNano2
• Planex GW-USValue-EZ
• Planex GW-USWExtreme
• Sitecom WL-365
• Solwise NET-WL-UMD-606N
• TRENDnet TEW-648UBM

Thanks, Damien, for this writeup. If you want to help Damien, please download and install a snapshot and plug in one of those newer devices, he's always interested in your test reports. If you want to support his work on 802.11n, Damien could use a couple of commercial APs to test against.