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Re: [PATCH] rt2800: Initialize max_txpower to MAX_G_TXPOWER and MAX_A_TXPOWER respectively

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Helmut Schaa wrote:
> Hi,
> 
> On Fri, May 18, 2012 at 1:04 AM, Tobias Diedrich
> <ranma+openwrt@xxxxxxxxxxxx> wrote:
> > rt2800: Initialize max_txpower to MAX_G_TXPOWER and MAX_A_TXPOWER
> > respectively, similar to how it is already done in rt2[45]00pci.c
> >
> > rt2800lib.c doesn't initialize max_power and thus after
> > http://git.kernel.org/?p=linux/kernel/git/linville/wireless-next.git;a=commitdiff;h=eccc068e8e84c8fe997115629925e0422a98e4de
> > was applied txpower is limited to 0 for these devices.
> >
> > This should be the proper fix compared to the net/wireless/reg.c
> > hack in http://patchwork.openwrt.org/patch/2165/
> >
> > (Patch against the OpenWRT compat-wireless version, but applies
> > equally well against wireless-next with a 19-line offset)
> >
> > Signed-off-by: Tobias Diedrich <ranma+openwrt@xxxxxxxxxxxx>
> >
> >
> > Index: compat-wireless-2012-04-17/drivers/net/wireless/rt2x00/rt2800lib.c
> > ===================================================================
> > --- compat-wireless-2012-04-17.orig/drivers/net/wireless/rt2x00/rt2800lib.c     2012-05-18 00:25:22.515271380 +0200
> > +++ compat-wireless-2012-04-17/drivers/net/wireless/rt2x00/rt2800lib.c  2012-05-18 00:28:48.809658951 +0200
> > @@ -4622,6 +4622,7 @@
> >        default_power2 = rt2x00_eeprom_addr(rt2x00dev, EEPROM_TXPOWER_BG2);
> >
> >        for (i = 0; i < 14; i++) {
> > +               info[i].max_power = MAX_G_TXPOWER;
> 
> 31dBm? That's ~1.3W.
> 
> I'd say we have to find a different way to deal with this issue.
> 
> Theoretically the device eeprom contains the allowed max tx power in
> EEPROM_EIRP_MAX_TX_POWER however most devices don't use this
> value at all :( so we cannot rely on it for most devices.

Yep, I looked at it for my device and I only found 0xff for both G
and A in there.  Maybe you could use max(eeprom_eirp, MAX_TXPOWER)
though...

> Typically the ralink devices are calibrated for 100% tx power. However,
> without EEPROM_EIRP_MAX_TX_POWER we don't know the real tx
> power of the device at all (have to consider antenna gain which should be
> part of EEPROM_EIRP_MAX_TX_POWER).
> 
> So, maybe we should do it the safe way and just register a safe default
> of 20dBm for all channels?

AFAIU that would cap you to 20dBm even if you are in a country that
has higher limits (e.g. 27dBm in the US?).

-- 
Tobias						PGP: http://8ef7ddba.uguu.de
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