From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753735AbbJZKv4 (ORCPT ); Mon, 26 Oct 2015 06:51:56 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:36323 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753586AbbJZKvs convert rfc822-to-8bit (ORCPT ); Mon, 26 Oct 2015 06:51:48 -0400 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT To: "Rafael J. Wysocki" , "Mark Brown" From: Michael Turquette In-Reply-To: Cc: "Rafael J. Wysocki" , "Rob Herring" , "Greg Kroah-Hartman" , "Tim Bird" , "frowand.list@gmail.com" , "Tomeu Vizoso" , "Russell King" , "Stephen Boyd" , "Vinod Koul" , "Dan Williams" , "Linus Walleij" , "Alexandre Courbot" , "Thierry Reding" , "David Airlie" , =?utf-8?q?Terje_Bergstr=C3=B6m?= , "Stephen Warren" , "Wolfram Sang" , "Grant Likely" , "Kishon Vijay Abraham I" , "Sebastian Reichel" , "Dmitry Eremin-Solenikov" , "David Woodhouse" , "Liam Girdwood" , "Felipe Balbi" , "Jingoo Han" , "Lee Jones" , "Jean-Christophe Plagniol-Villard" , "Tomi Valkeinen" , "linux-kernel@vger.kernel.org" , "linux-clk@vger.kernel.org" , "dmaengine@vger.kernel.org" , "linux-gpio@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-tegra@vger.kernel.org" , "linux-i2c@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-pm@vger.kernel.org" , "Linux PWM List" , "linux-usb@vger.kernel.org" , "linux-fbdev@vger.kernel.org" References: <20151018192931.GY14956@sirena.org.uk> <562A5602.7000208@sonymobile.com> <24100858.2KIS8Y2npV@vostro.rjw.lan> <20151024220648.GR29919@sirena.org.uk> Message-ID: <20151026105138.20687.13546@quantum> User-Agent: alot/0.3.6 Subject: Re: [GIT PULL] On-demand device probing Date: Mon, 26 Oct 2015 03:51:38 -0700 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Rafael J. Wysocki (2015-10-25 06:54:39) > On Sun, Oct 25, 2015 at 12:06 AM, Mark Brown wrote: > > On Sat, Oct 24, 2015 at 04:17:12PM +0200, Rafael J. Wysocki wrote: > > > >> Well, I'm not quite sure why exactly everyone is so focused on probing here. > > > > Probe deferral is really noisy even if it's working fine on a given > > system so it's constantly being highlighted to people in a way that > > other issues aren't if you're not directly having problems. > > > > There's also the understanding people had that the order things get > > bound changes the ordering for some of the other cases (perhaps it's a > > good idea to do that, it seems likely to be sensible?). > > But it really doesn't do that. Also making it do so doesn't help much > in the cases where things can happen asynchronously (system > suspend/resume, runtime PM). > > If, instead, there was a way to specify a functional dependency at the > device registration time, it might be used to change the order of > everything relevant, including probe. That should help to reduce the > noise you're referring to. Taking it a step further, if functional dependencies were understood at link-time then we could optimize link order as well. There are probably lots of optimizations if we only made the effort to understand these dependencies earlier. Constructing the device/resource dependency graph before the device ever boots sounds interesting to me. Regards, Mike > > If the dependency could only be discovered at the probe time, the > order of things might be changed in response to letting the driver > core know about it rather than "just in case", which should be more > efficient. > > Thanks, > Rafael