signal quality, prism firmware, WPA

Tony Espy espy at
Mon Dec 12 18:48:38 EST 2005

I've reported this problem multiple times.  We also are using a PCMCIA 
based Prism card.  I reported a patch for v0.3.9 of the driver awhile 
back ( see below ).

What I found was that the method hostap_join_ap() in hostap_ioctl.c 
could end up passing a channel number of 0 to the firmware when it sent 
a JOINREQUEST.  This was due to the fact that there were two seperate 
arrays that could hold scan results, one called scan_results and one 
called hostscan_results.

For details and a copy of the patch we're currently running with see my 
original post at:

Let me know if you have any questions.

Tony Espy
Pepper Computer

Paul Fox wrote:
> hi -- i have a very repeatable problem i'm hoping someone here
> can shed light on.
> we're using PCMCIA cards based on the (now Intersil) Prism 2.5
> chipset.  the cards are the Engenius (or Senao) NL-2511CD Plus,
> like this:
> as shipped, the cards we've gotten have firmware version 1.4.9,
> which works just fine with WEP and the hostap drivers (version
> 0.3.9).  (we're not using hostapd -- we're just a station.)
> however, we need WPA.  so i've upgraded some of our cards to
> 1.8.4.  (i've also tried intermediate versions, like 1.7.1, with
> similar results.)  device identification currently looks like this:
>     wifi0: NIC: id=0x800c v1.0.0
>     wifi0: PRI: id=0x15 v1.1.1
>     wifi0: STA: id=0x1f v1.8.4
> when using WEP, everything still works fine, just as it did with 1.4.9.
> however, when using WPA, the signal quality, strength, and noise
> values all report bogus results.  signal quality is consistently
> reported as 0, strength and noise report as a constant non-zero
> value.  (i've verified this at a low level with driver printks, so
> specific tool versions can be eliminated i think.)
> there are two RID values for fetching these parameters -- one is
> "raw" (HFA384X_RID_COMMSQUALITY, or 0xFD43) and the other is
> newer, with results in dbm (HFA384X_RID_DBMCOMMSQUALITY, or
> 0xFD51).  normally with newer firmware the latter RID command
> is used.  i modified the driver to force the older api, and
> the results are the same -- quality is consistently 0, strength
> and noise are unvarying non-zero numbers.
> i have (legitimate) access to the prism driver programmers
> manual, and from what i can tell, the hostap driver is using the
> API correctly.  (and, indeed, it seems to work just fine when WPA
> isn't involved.)
> testing the 1.8.4 firmware in a windows laptop shows that, as
> expected, quality and strength values are somehow available,
> since the prism driver and status utility report the values
> without complaining.
> has anyone else seen this behavior?  i've found references to
> similar problems in the list archives, but the messages were
> almost two years old...
> many thanks in advance.
> (so far the only oddness i've noticed is what i've detailed here. 
> are there other stats i should be checking in particular to see
> if they're also not reported correctly?)
> paul
> =---------------------
>  paul fox, pgf at
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