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Post subject: Can't compile/load acx module in kernel 2.6.36-0.slh.3  PostPosted: 17.12.2010, 03:01

Joined: 2010-10-01
Posts: 288

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I am trying to use an old D-Link DWL-520+ wifi adapter with TI ACX111 chipset and acx100 driver, which I've successfully used in the past. However, the acx100 module from Debian Sid (version 20080210-1.1) wouldn't compile with the 2.6.36-0.slh.3-aptosid-amd64 kernel I have on that box, throwing an error about /include/linux/utsrelease.h not found. I checked and utsrelease.h is in /include/generated/ in the headers for that kernel, so I modified pci.c and then the module compiled. But, it won't load, throwing
Error inserting acx: Unknown symbol in module

and dmesg shows
acx: Unknown symbol acxusb_i_tx_timeout (err 0)

If I try to force the module to load with
modprobe -f acx

it gives
Invalid module format

The same module compiles and loads on the other 2.6.32 sidux kernel I have on that machine, but it seems very unstable and locked up the machine a couple of times. I'm probably going to get another wifi adapter because acx100 doesn't seem to support the needed WPA encryption, but I'm wondering if anyone has had success compiling or using this module in Aptosid? I can't easily upgrade that system as it has no internet access currently.
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Post subject: RE: Can  PostPosted: 17.12.2010, 23:25

Joined: 2010-08-25
Posts: 954

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I'm afraid it's time to retire those TI ACX100/ ACX111 chipsets, especially as well supported USB wlan cards surpassing the abilities of those chipsets are available for 6-20 EUR, with PCI/ mini-PCI also starting in that range.

Regarding the background: Several years ago, two developers actively tried to get "tiacx" into the mainline kernel. They got pretty far from the legacy "acx" driver in relatively short time - until they were asked about the origin of their code and the cleanliness of their reverse engineering, as there were striking similarities to some leaked proprietary code from Texas Intruments... In addition the sudden appearance of their driver, after earlier attempts never went far for years, was rather suspicious, however neither of those developers ever came up with an answer, even more, they completely vanished and left their efforts abandoned. Since 2006, the existing code base has to be considered tainted and no developer really dared to take it up again - or to restart writing a driver from scratch, especially as more capable/ interesting hardware appeared on the market meanwhile. In other words no real development was dedicated to those chipsets for about 4 years by now, which is at least two eternities in linux these days.

But let's take a look at the capabilities the "acx" driver provided back then, while it still had some attention - or rather what it didn't provide. There was (and is) no kind of WPA support in the driver, while ACX100 hardware only supports WPA1/ TKIP (an encryption methods which has to be considered broken these days) and ACX111 hardware supports WPA2/ AES as well. Furthermore the "acx" driver has always been very noisy and never really got to a state of being "stable". While it's likely quite possible to forward port "acx" to newer kernels, this doesn't change that the driver has never really been usable in the first place - even disregarding all legal implications.

The "acx" package is maintained in Debian (we avoid it for legal implications - and because its current state of brokeness simply doesn't justify dealing with a legally encumbered package), which at this stage is still frozen on kernel 2.6.32, so this means within the scope of Debian, "acx" is still functional. However a bug filed at low priority might still yield in an upgrade fixing your compile issues.

These days, the landscape for wlan support in linux has become a lot better, pretty much all of the remaining vendors developing wlan chipsets have recognized the importance and market impetus of mainline driver support for their chipsets - or were simply forced to provide functional drivers by large OEM customers. Even Texas Instruments is actively developing a driver for the direct descendants of those legacy ACX100/ ACX111 chipsets, namely wl1251/ wl1271 (almost exclusively targetted at embedded device, aka smartphones). But like most other traditionally closed source vendors, these efforts only target current or even upcoming chipset generations and largely ignore legacy ones.

In other words, I wouldn't take any bets on hardware support for ACX100/ ACX111 going anywhere, switching to a wlan chipset with well supported mainline drivers is neither difficult nor overly expensive these days, but saves a lot of trouble.
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