Since development kernels 2.6.26-rc*, the iwlwifi drivers (iwl3945, iwl4965) have LED support. While LED support is nice to have (making it easy to see when the wireless connection is available), the blinking of the LED whenever there is data transmitted is annoying.

In most networks, there is a constant chatter on the net. Windows server browsing and announcing, Zeroconf/Bonjour announcements, Printer discovery. When you're using some instant messaging or chat such as IRC there is some data transmitted all the time. Your email program might be polling for new emails, and your weather applet might be fecthing the latest forecasts. So basically, there always is ome network traffic. Often in the range of less than 1k/s, but there is.

The new iwlwifi drivers don't flicker the LED with each packet received, but apparently will just set the LED to a blink mode when they received or transmitted some data, which if find rather irritating.

Fortunately, this can easily be configured in Linux, just save this script in /etc/network/if-up.d/iwl-no-blink and make it executable:

#!/bin/sh
if [ "$IFACE" = "wlan0" ]; then
	for dir in /sys/class/leds/iwl-phy*X; do
		echo none > $dir/trigger
	done
fi

This is a quick hack, but it does the job well for me - when the device is connected it will stop blinking on data. It will still blink when connecting (leds:iwl-phy*:assoc) and indicate if the connection is available (leds:iwl-phy*:radio).