Re: Scan fails to find wireless networks

On Mon, Oct 11, 2004 at 03:44:12AM +0200, Joerg Albert wrote:
> On Fri, 1 Oct 2004, Mike Pinna wrote:
> Loading the driver (e.g. triggered by plugging the device in or starting
> the USB subsys) does only initialize it. It starts after the netdevice is
> opened, e.g. by
> 	ifconfig wlan0 up
> Guess that makes the difference in your case, I doubt that you need it to
> be connected to an access point.

You are quite right, thank you.  That aspect works fine now.

After I have brought up the interface would you expect it to work
immediately, or is it expected that for some time data sent on the
interface might be lost?  I'm consistently getting behaviour like the
following, with apparently complete packet loss for around six seconds
after the interface comes up:

# ifconfig wlan0 down; ifconfig wlan0 192.168.5.78; ping 192.168.5.1
PING 192.168.5.1 (192.168.5.1): 56 data bytes
64 bytes from 192.168.5.1: icmp_seq=6 ttl=64 time=28.3 ms
64 bytes from 192.168.5.1: icmp_seq=7 ttl=64 time=13.8 ms
64 bytes from 192.168.5.1: icmp_seq=8 ttl=64 time=13.7 ms
64 bytes from 192.168.5.1: icmp_seq=9 ttl=64 time=13.5 ms
--- 192.168.5.1 ping statistics ---
10 packets transmitted, 4 packets received, 60% packet loss

This affects all data transfer consistently for that amount of time, not
just ping. 

[ assertion failures on arm ]
> What did you run before the "ifconfig" here, a "iwlist wlan0 scan"?

Yes.  I can reproduce this as follows, immediately after loading the
modules:

# iwlist wlan0 scan
wlan0     No scan results
# ifconfig wlan0 127.0.0.2
at76c503.c: at76c503.c:2905 assertion dev->istate == INIT failed
#

I could probably reproduce the `dev->istate == SCANNING' assertion
failure easily enough if that would be interesting.

Also I'm having another problem that is rather serious for me, which is
that scanning for networks often fails to come up with anything near a
complete list of available networks.  There should be five networks
discovered, but often I only see as few as one or zero.  My driver is
the at76c505-rfmd2958 with version 1.101.0 #86 of the firmware.

Is it possible a newer version of the firmware will help with this?
I've tried it with the same device under Windows and it seemed to work a
lot better with the binary drivers that came with the device, though
it's hard to know what was going on behind the scenes and extracting the
firmware from those drivers for use with your driver caused little or no
improvement.

Other wireless networking hardware we've tried (mainly PCMCIA) has no
problem finding all networks in a scan under linux.

Thanks very much for any ideas on these questions,
Mike