From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966285AbdADSTK (ORCPT ); Wed, 4 Jan 2017 13:19:10 -0500 Received: from foss.arm.com ([217.140.101.70]:55974 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753702AbdADSR5 (ORCPT ); Wed, 4 Jan 2017 13:17:57 -0500 Date: Wed, 4 Jan 2017 18:17:18 +0000 From: Will Deacon To: Mark Rutland Cc: Russell King - ARM Linux , Alexander Stein , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2 2/2] arm: perf: Mark as non-removable Message-ID: <20170104181717.GT18193@arm.com> References: <20161221150340.25657-1-alexander.stein@systec-electronic.com> <20161221150340.25657-3-alexander.stein@systec-electronic.com> <20161222224547.GA30170@remoulade> <2559413.O5mI12kdOo@ws-stein> <20170104113025.GE8329@leverpostej> <20170104114056.GO14217@n2100.armlinux.org.uk> <20170104114612.GF8329@leverpostej> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170104114612.GF8329@leverpostej> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 04, 2017 at 11:46:13AM +0000, Mark Rutland wrote: > On Wed, Jan 04, 2017 at 11:40:56AM +0000, Russell King - ARM Linux wrote: > > On Wed, Jan 04, 2017 at 11:30:25AM +0000, Mark Rutland wrote: > > > On Wed, Jan 04, 2017 at 10:19:46AM +0100, Alexander Stein wrote: > > > > I'm not sure if the change above works with remove functions set in struct > > > > bus_type too. > > > > But on the other hand this would hide errors in drivers which are actually > > > > removable but do not cleanup properly which DEBUG_TEST_DRIVER_REMOVE tries to > > > > detect. > > > > By setting .suppress_bind_attrs = true explicitely you state "This > > > > driver cannot be removed!", so the remove callback is not missing by accident. > > > > > > I'm not sure I follow. If the remove callback is accidentally missing, > > > the driver is not "actually removable" today -- there's either no remove > > > code, or it's not been wired up (the latter of which will likely result > > > in a compiler warning about an unused function). > > > > > > Aborting the remove early in those cases is much safer than forcefully > > > removing a driver without a remove callback. > > > > Drivers without a remove function may be removable - there's more layers > > than just the driver - there's the bus layer as well, which may or may > > not direct to a private-bus pointer. > > Sure; which is why I initially suggested doing something at the bus > layer. That way, each layer could do any necessary check, and/or > delegate to a callback for the layer below. > > > There's no real way for the core driver model code to know whether the > > lack of the ->remove in the struct device_driver is something that > > prevents a driver being removed, or whether it's handled via some other > > method. Eg, platform drivers. > > While true today, my suggestion is to add the infrastrucutre such that > it can. That seems nicer to me than each driver having to retain > (redundant) state. > > Regardless, this patch itself is fine. Well, it's also largely incomplete as you point out, so I don't think we gain an awful lot from merging it as-is. Will