From: Christian Lamparter <chunkeey@googlemail.com>
To: Andrew Wasielewski <andrew@wasielewski.co.uk>
Subject: Re: WARNING: at drivers/net/wireless/p54/main.c:443 p54_work+0x66/0x80 [p54common]() (Not tainted)
Date: Thu, 7 Feb 2013 16:57:12 +0100
Cc: linux-wireless@vger.kernel.org
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Hello Andrew

On Thursday, February 07, 2013 12:51:38 AM Andrew Wasielewski wrote:
> On Wednesday 30 January 2013 01:06:52 Christian Lamparter wrote:
> > On Wednesday, January 30, 2013 12:04:38 AM Andrew Wasielewski wrote:
> > > The "failed to update LEDs" messages continued until I rebooted - couldn't find
> > > a way to reload the stack. O/S is ClearOS Community release 6.3.0 (kernel 2.6.32-279.19.1.v6.i686).
> > > Hardware is LinkSys WUSB54G running in AP mode using hostapd, firmware isl3886usb.
> > Reloading the driver (modprobe -r p54usb && modprobe p54usb) or replugging the 
> > device should have helped. Anyway, the clean "reset" procedure for these devices
> > is known but to Conexant. If you have sysfs, you can reset a dead usb device
> > by toggling (writing 0 and then 1 into) /sys/bus/usb/devices/x-y-z/authorized.
> The "authorized" file doesn't exist in my sysfs
> > If this helps, we can at least let the driver reset the device automatically
> > once it bails out. What do you think?
> 
> modprobing p54usb works with the driver, but I still have to restart hostapd for
> it to pick up the now-working driver.  Good news is it hasn't happened again.
Ah, you should be able to do this automatically. For example with Debian
(and Ubuntu?) you can add an entry into your /etc/network/interfaces:

[use tabs]
allow-hotplug wlan0
iface wlan0 inet manual
	hostapd /etc/hostapd/hostapd.conf
	up /sbin/ifconfig "$IFACE" 192.168.0.254 netmask 255.255.255.0 

and it will automatically restart hostapd when the device
is replugged/driver is reloaded.
[Note: The driver can detect if the firmware is dead. I'm
thinking about implementing a simple reset-when-dead feature.
Would you be willing to test it once it materializes? I'm
asking because I don't have any isl3886usb. Just the PCI
versions and two isl3887usb].

> Unplugging is tricky as I have slightly hacked the WUSB54G to fit inside the case
> (an old Shuttle mini-PC) with a SMA-RP connector and a decent antenna.  In fact the
> main reason I went for the WUSB54G is because this conversion seemed quite easy.  
> I am open to any suggestions for USB devices with b/g/n(?) support that could be
> internally mounted in this way, + has AP mode support of course.
Ah, well the USB + AP requirement is sort of a problem. Usually everyone favourit
and well-tested WiFi-AP is some sort of a PCI or PCIe solution. But still, there 
are a few alternatives. The most popular are based on:
 - ath9k_htc 
 - rt2800usb

Unfortunately, I can't tell if they are adequate for your needs. Some
people have posted "stability comparision" between those. But I can't
find any from recent times. Of course, if you are curious and don't mind
spending 1-10 GBP [per device], you can do your own little experiments
about cheap USB+AP solutions. I'm sure other people would be interested
in the results too [that's a hint ;)].

Regards

Christian