maemo.org Bugzilla – Bug 9146
iwconfig reports non-zero transmit power when interface is powered down
Last modified: 2010-03-02 09:18:34 UTC
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EXACT STEPS LEADING TO PROBLEM:
(Explain in detail what you do (e.g. tap on OK) and what you see (e.g. message
Connection Failed appears))
1. Turn the phone on
2. Run "/sbin/iwconfig" in termimal - shows Tx=Power=0 dBm in wlan0 section
(iwconfig is in wireless-tools package)
3. Tap on status area and then tap 'Internet connection' button. A list of
access points is presented.
4. Don't select any (tap outside "Select connection" area to cancel)
5. Run "/sbin/iwconfig" in termimal - shows Tx-Power=20 dBm in wlan0 section
6. Press the power button on phone and select "Offline mode"
7. Run "/sbin/iwconfig" in termimal - still shows Tx-Power=20 dBm in wlan0
Wireless radio should be disabled. Running "/sbin/iwconfig" should show
Tx-Power=off (this happens when I enable a wifi kill switch or running "sudo
rfkill block 0" on a laptop)
Wifi radio appears to be still transmitting signals from the interpretation of
/sbin/iwconfig showing Tx-Power=(some number) dBm instead if Tx-Power=off.
EXTRA SOFTWARE INSTALLED:
If the radio is transmitting even in offline mode, this may be unacceptable for
use in an aircraft. May also be contributing to battery drainage.
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:18.104.22.168)
Gecko/20100106 Ubuntu/9.10 (karmic) Firefox/3.5.7
Hi Jon, thanks for reporting this!
Confirmed. An "rmmod wl12xx; modprobe wl12xx" cycle makes it drop back to 0dBm
until it is used again.
This is a cosmetic issue, whilst it appears the radio is still on it has
actually been powered down, hence why the signal strength remains the same. You
can prove this to yourself by moving away from the access point and noting that
the signal strength does not change.
You might also like to check your syslog, "wlan0 is DOWN" message is emitted to
the log the when the radio is switched off. The "firmware booted" message
appears when the radio is powered back on.
I have tested via this method, with a sniffer and also by measuring the
However I will investigate why iwconfig is reading old values.
Thanks, updating summary & keywords accordingly.