Subject: Re: RFC Patch v2: Add signal strength to nl80211station info
From: Johannes Berg <johannes@sipsolutions.net>
To: Henning Rogge <hrogge@googlemail.com>
Cc: Henning Rogge <rogge@fgan.de>,
	"Luis R. Rodriguez" <lrodriguez@atheros.com>,
	Luis Rodriguez <Luis.Rodriguez@atheros.com>,
	Marcel Holtmann <holtmann@linux.intel.com>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	"nbd@openwrt.org" <nbd@openwrt.org>
In-Reply-To: <200812061646.36044.hrogge@googlemail.com> (sfid-20081206_164640_445951_82A87A7B)
References: <200811252131.30161.hrogge@googlemail.com>
	 <1228575081.16752.8.camel@johannes.berg>
	 <200812061603.21930.hrogge@googlemail.com>
	 <200812061646.36044.hrogge@googlemail.com>
	 (sfid-20081206_164640_445951_82A87A7B)
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Date: Sat, 06 Dec 2008 16:59:32 +0100
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On Sat, 2008-12-06 at 16:46 +0100, Henning Rogge wrote:
> On Saturday 06 December 2008 16:03:16 Henning Rogge wrote:
> > > I'd rename _TOTAL to _LEGACY and remove the calculation for MCS rates=
,
> > > that way it's obviously clear what you're getting in userland.
> Okay, after reading your mail a second time I understood you...=20
>=20
> I think with removing the total bitrate for 802.11n we will just make the=
=20
> userspace interface more complex. You will have to look at four different=
=20
> things (flags, MCS, guard interval, legacy) just to get the bitrate, whic=
h=20
> will be the typical information the user wants to know. Is there anything=
=20
> nl80211 will gain if we don't put this value inside for all 802.11 ? We c=
annot=20
> drop it because of 802.11abg, so why not fill it with useful data ?

For one, I'm a bit concerned that the calculation is fairly complex, and
may not always be necessary; especially divisions can be expensive on
some CPUs.

Also, there are duplicate numbers possible, so just the pure bitrate
will _not_ actually be "the typical information" because it's not
specific enough, when debugging, for example, you will probably need to
know whether it's short-gi or not.

johannes

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