RFC: powerd Patch & proposed future changes [wifi tx power]
Sam Leffler
sam at freebsd.org
Mon Jul 6 17:31:21 UTC 2009
Aragon Gouveia wrote:
> Rene Schickbauer wrote:
>> Hi!
>>
>>> I think this is a very nice idea, especially the TFT backlight part. It
>>> also might be useful to adjust the WiFi transmit power level according
>>> to battery state. That can also save some power, especially on
>>> portables.
>>
>> Yes, changing the transmit power would be possible. Although
>> adjusting the
>> transmit power via script on a *mobile* computer is likely to get the
>> user
>> offline rather quickly.
>>
>> On the other hand, powerd would just run a script. This script could
>> start a
>> user-written daemon to continually adjust power level.. and when ac is
>> plugged in again, the script kills that daemon. I sincerely doubt
>> that would
>> save you any amount of power worth mentioning, though but may give you
>> additional troubles. But maybe you could restrict an a/b/g card to
>> b/g or a
>> and thus save some power.
>
> FWIW, changing transmit power on my Intel 4965 based system made zero
> difference to overall power consumption.
Changing the tx power is unlikely to save you much. What you want to do
is switch between sta mode power save when you switch between AC and
battery and/or change the PS parameters depending on the power config
and battery level. I don't recall if iwn is hooked up properly to
ifconfig to control power save operation.
FWIW wifi tx power control (TPC) is best used to avoid saturating the rx
radio when in close proximity. It's also good to reduce the power so
you don't splatter adjacent channels (mostly in 2.4GHz). Some devices
do this automatically.
Sam
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