Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:42318 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752361AbYKSUQO (ORCPT ); Wed, 19 Nov 2008 15:16:14 -0500 Date: Wed, 19 Nov 2008 15:08:57 -0500 From: "John W. Linville" To: Andrey Borzenkov Cc: Pavel Roskin , linux-wireless@vger.kernel.org Subject: Re: [PATCH] wireless: sysfs was displaying different values for level and noise than procfs Message-ID: <20081119200856.GH3485@tuxdriver.com> (sfid-20081119_211618_374240_B56BC66B) References: <200811151831.26403.arvidjaar@mail.ru> <1227122019.2196.14.camel@dv> <200811192245.29487.arvidjaar@mail.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <200811192245.29487.arvidjaar@mail.ru> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, Nov 19, 2008 at 10:45:21PM +0300, Andrey Borzenkov wrote: > On Wednesday 19 November 2008, Pavel Roskin wrote: > > On Sat, 2008-11-15 at 18:31 +0300, Andrey Borzenkov wrote: > > > Subject: [PATCH] wireless: sysfs was displaying different values for level and noise than procfs > > > From: Andrey Borzenkov > > > > > > /proc/net/wireless asjusts display of signal and noise level depending on > > > whether units are percentage or dBm. Use the same format in sysfs. This > > > makes it easy to know unit - below zero is dBm, above zero is percent. > > > > I've seen received power up to 3 dBm. The AP was using an amplifier > > (it's specialized hardware), and it's possible that the card on the > > station side was exaggerating the signal. However, the data we report > > should not need any guesswork to be interpreted. It may be parsed by > > userspace software. > > > > But positive dBm is not even possible to represnt right now. It is u8 and > is displayed as ((s32)level - 256); so it is *always* negative. > > > Receiving 1 mW out of 200 mW is not impossible in some antenna > > configurations even with consumer devices. > > > > > Before: > > > {pts/1}% cat /sys/class/net/eth1/wireless/level > > > 203 > > > {pts/1}% cat /sys/class/net/eth1/wireless/noise > > > 166 > > > > > + return sprintf(buf, format_string, (__s32)iw->field - \ > > > + ((iw->qual.updated & IW_QUAL_DBM) ? 0x100 : 0)); \ > > > > I think non-dBm data should be shown in a special format: "203/255" > > where 255 is the maximal value, and the dBm data should be shown as > > numbers: "-48". This way, we encourage use of dBm data by making it > > easier to parse. > > > > Well, I do not have any strong opinion regarding this; I just noticed > discrepancy between procfs and sysfs for what effectively is the same raw > value. And what is your perspective regarding potential 'userland ABI' issues of either this patch or of Pavel's suggestion? John -- John W. Linville Linux should be at the core linville@tuxdriver.com of your literate lifestyle.