On Mon, 26 Apr 2004, Matt Brown wrote:
> Jumping back to a thread from earlier in the month regarding transmit
> power levels. Pavel stated:
>
> > I'm not going to apply the patch for tx power any time soon. The
> > reason is that the maintainers could be held responsible for possible
> > bugs. If the driver sets power level incorrectly and the users
> > violate local regulations thinking that they set allowed levels, the
> > authors of the code could be held responsible, GPL notwithstanding.
> >
> > I don"t have any documentation for the tx power settings. I'd have to
> > measure the transmitted signal to see if the setting is correct. I
> > don"t have any equipment to make sure that the tx power is the same as
> > the driver is requested to set.
> >
> > So it's probably going to stay a separate patch or distribution. If
> > somebody sends me documentation for the power levels and a documented
> > patch I may merge the code. Otherwise I"m not going to take this
> > responsibility.
>
> I am assuming this statement holds true for most (all?) cards supported
> by the orinoco driver? None of the cards I have access to seem to
> support setting the transmit power.
Actually, you quoted several statements. The patch supports tx power
setting for Symbol firmware only. The lack of documentation is common for
all firmwares.
Agere:
wl_lkm_718 defines RID 0xFC2A as CFG_CNF_TX_POW_LVL, but it's never used.
The RID is missing in 6.16 and 8.72 firmwares. Presumably it appeared in
9.xx firmwares.
Symbol:
The driver from http://ftp.nentec.de/dl/wlan/ uses RID 0xFC8E to set Tx
power. However, I don't see any reference to that RID in the Symbol's
driver. Value 0 corresponds to 20 dBm. This value is default for both
D-Link 650H, which is a high-power card, and Symbol's CF card, which is
hardly high-power.
Intersil:
HostAP has commented out code to set Tx power using registers of the
baseband processor. The comment says that the correct implementation
should use another register to measure the actual output. RID 0xFCBE is
called HFA384X_RID_TXPOWERMAX but it's not used. Most likely it
corresponds to PDR 0x409 (USB Max Power), which is USB specific.
> While I don't have access to any documentation that would be helpful for
> this problem, we (www.wand.net.nz) do have access to equipment that
> could be used to measure the transmitted power. If we were to offer to
> test the transmitted power of the card would it help to get this support
> merged into the code or are there still other problems that you would
> need to deal with?
There is a significant probability that the same RID value has different
meanings for different cards. Also, it's possible that some settings
would have no effects for some hardware.
> Setting transmit power would be a valuable feature for us in the driver
> as the local regulations do not allow us to attach a 200mW card to a
> 24dBi antenna. Unfortunately for us the most easily obtainable miniPCI
> cards are often 200mW.
That's exactly the case where settings that have no effect would be a
problem. You may want to talk to the card vendor and explain your
concern. I hope they will care about local regulations.
If the cards have Intersil firmware, you could try to resurrect the
code for HostAP and measure the actual output.
--
Regards,
Pavel Roskin
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