BMC4312 power management

NoOp glgxg at sbcglobal.net
Fri Jun 18 01:18:44 UTC 2010


On 06/16/2010 10:43 AM, mchl2005 at gmail.com wrote:
> I've been looking into this lately and can't seem to find anything useful.
> When running 'sudo iwlist eth1 txpower', I get the following:
> eth1      2 available transmit-powers :
>       0 dBm      (1 mW)
>       25 dBm      (255 mW)
>           Current Tx-Power:32 dBm      (1496 mW)
> 
> There seems to be way to change it, for example:
> sudo iwconfig eth1 txpower 25
> Error for wireless request "Set Tx Power" (8B26) :
>     SET failed on device eth1 ; Operation not supported.
> 
> ... and every other value I tried resulted in the same error message.

This may lead to a clue:
<http://www.insecure.ws/2010/06/05/wifi-cards-txpower-linux-mac80211-and-regulations>

BTW: on my laptop:
wlan0     unknown transmit-power information.
          Current Tx-Power=14 dBm  	(25 mW)

Now if I try to set the power to 20, I get:
$ sudo iwconfig wlan0 txpower 20
Error for wireless request "Set Tx Power" (8B26) :
    SET failed on device wlan0 ; Invalid argument.

However if I set it for 10 it works:
$ sudo iwconfig wlan0 txpower 10
$ sudo iwlist wlan0 txpower
wlan0     unknown transmit-power information.
          Current Tx-Power=10 dBm  	(10 mW)

And set it to auto:
$ sudo iwconfig wlan0 txpower auto
it goes back to 14:
 sudo iwlist wlan0 txpower
wlan0     unknown transmit-power information.
          Current Tx-Power=14 dBm  	(25 mW)

Your readings also seem a bit odd. From 'man iwconfig':
====
txpower
      For cards supporting multiple transmit powers, sets the transmit
      power in dBm. If W is the power in Watt, the power in dBm is P =
      30  +  10.log(W).   If  the value is postfixed by mW, it will be
      automatically converted to dBm.
      In addition, on and off enable and disable the radio,  and  auto
      and  fixed  enable  and disable power control (if those features
      are available).
              Examples :
                   iwconfig eth0 txpower 15
                   iwconfig eth0 txpower 30mW
                   iwconfig eth0 txpower auto
                   iwconfig eth0 txpower off
====

Does:

$ sudo iwconfig eth1 txpower 25mW

or similar work?

<http://www.google.com/search?hl=en&complete=0&q="Current+Tx-Power%3A32+dBm"&btnG=Search>





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