From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759847Ab2COO1H (ORCPT ); Thu, 15 Mar 2012 10:27:07 -0400 Received: from kirsty.vergenet.net ([202.4.237.240]:46176 "EHLO kirsty.vergenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756015Ab2COO1D (ORCPT ); Thu, 15 Mar 2012 10:27:03 -0400 Date: Thu, 15 Mar 2012 23:26:58 +0900 From: Simon Horman To: Mark Brown Cc: Liam Girdwood , linux-kernel@vger.kernel.org Subject: Re: [PATCH] regulator: notify sysfs when voltage is set Message-ID: <20120315142657.GD3129@verge.net.au> References: <1331813073-714-1-git-send-email-horms@verge.net.au> <20120315124631.GJ3138@opensource.wolfsonmicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120315124631.GJ3138@opensource.wolfsonmicro.com> Organisation: Horms Solutions Ltd. User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2012 at 12:46:31PM +0000, Mark Brown wrote: > On Thu, Mar 15, 2012 at 09:04:33PM +0900, Simon Horman wrote: > > > This allows libudev to be used to monitor voltage changes and thus allows > > user-space code to avoid polling the sysfs entry for changes. > > I notice that we don't generate similar events for cpufreq... what are > the performance implications from firing off udev (which isn't free) > every time we scale the CPU frequency? It feels like this might be > disruptive, especially with a governor like ondemand which responds to > system load. Hi Mark, that is a good point and to be honest not one that I had considered. For the use-case that I have in mind, which is basically to log voltage changes over time, it may be acceptable to rate-limit notifications somehow. But at that point I may be better off just polling. Out of interest, how often can ondemand potentially change the voltage?