From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753544Ab1JHSSp (ORCPT ); Sat, 8 Oct 2011 14:18:45 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:37813 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752978Ab1JHSSn (ORCPT ); Sat, 8 Oct 2011 14:18:43 -0400 X-Originating-IP: 217.70.178.141 X-Originating-IP: 50.43.15.19 Date: Sat, 8 Oct 2011 11:18:29 -0700 From: Josh Triplett To: Greg KH Cc: "G, Manjunath Kondaiah" , linux-arm-kernel@lists.infradead.org, Grant Likely , linux-omap@vger.kernel.org, linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Dilan Lee , Mark Brown , Manjunath@jasper.es Subject: Re: [PATCH 2/5] drivercore: Add driver probe deferral mechanism Message-ID: <20111008181829.GB15617@leaf> References: <1317963790-29426-1-git-send-email-manjugk@ti.com> <1317963790-29426-3-git-send-email-manjugk@ti.com> <20111007064928.GE27508@kroah.com> <20111007205715.GC5275@leaf> <20111007212326.GA29003@kroah.com> <20111008040351.GA7694@leaf> <20111008155502.GB616@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111008155502.GB616@kroah.com> 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 Sat, Oct 08, 2011 at 08:55:02AM -0700, Greg KH wrote: > On Fri, Oct 07, 2011 at 09:03:51PM -0700, Josh Triplett wrote: > > On Fri, Oct 07, 2011 at 02:23:26PM -0700, Greg KH wrote: > > > On Fri, Oct 07, 2011 at 01:57:15PM -0700, Josh Triplett wrote: > > > > On Thu, Oct 06, 2011 at 11:49:28PM -0700, Greg KH wrote: > > > > > On Fri, Oct 07, 2011 at 10:33:07AM +0500, G, Manjunath Kondaiah wrote: > > > > > > +config PROBE_DEFER > > > > > > + bool "Deferred Driver Probe" > > > > > > + default y > > > > > > + help > > > > > > + This option provides deferring driver probe if it has dependency on > > > > > > + other driver. Without this feature, initcall ordering should be done > > > > > > + manually to resolve driver dependencies. This feature completely side > > > > > > + steps the issues by allowing driver registration to occur in any > > > > > > + order, and any driver can request to be retried after a few more other > > > > > > + drivers get probed. > > > > > > > > > > Why is this even an option? Why would you ever want it disabled? Why > > > > > does it need to be selected? > > > > > > > > > > If you are going to default something to 'y' then just make it so it > > > > > can't be turned off any other way by just not making it an option at > > > > > all. > > > > > > > > Given that the drivers which use this mechanism will not necessarily get > > > > built into the kernel, I'd suggest that it should remain optional and > > > > default to n. Those drivers can then add a dependency on PROBE_DEFER. > > > > Let's try to avoid adding more infrastructure to the kernel that takes > > > > up space even when unused; certainly embedded will appreciate not having > > > > this feature unless a driver needs it. > > > > > > How much extra space is this "feature" really? > > > > Just checked: 776 bytes, 640 of text and 136 of data. We have kconfig > > options for comparable amounts. > > > > > I don't see it being > > > anything larger than the amount of memory increase that just happened as > > > I typed this email as part of the ongoing memory density changes. > > > > I don't know about the changes you mean > > Moore's law. Ah, I see. For new systems, sure; for systems or mechanisms with a pre-existing size constraint, that doesn't help. > Really, 776 bytes, just always enable it, it's not worth it. 776 bytes alone, no; 776 bytes times the next (or previous) thousand features, yes. - Josh Triplett