From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Wed, 30 Sep 2015 16:39:30 +0100 Subject: [PATCH 1/4] of: Add of_parse_phandle_with_opt_args() helper function In-Reply-To: <1442944336-11754-2-git-send-email-marc.zyngier@arm.com> References: <1442944336-11754-1-git-send-email-marc.zyngier@arm.com> <1442944336-11754-2-git-send-email-marc.zyngier@arm.com> Message-ID: <560C0232.2010100@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Marc, On 22/09/15 18:52, Marc Zyngier wrote: > of_parse_phandle_with_args() is slightly inflexible as it doesn't > allow the (unusual) case where the #*-cells property is not defined. > In order to support this, introduce of_parse_phandle_with_opt_args() > which assumes that #*-cells is zero when it is not defined, > as required by the msi-parent binding > > This is done by turning __of_parse_phandle_with_args into an even > bigger monster, which is a bit frightening. A monster indeed; I can't quite figure out the exact effect this change has on of_count_phandle_with_args(), but I have a lingering doubt it may be something undesirable, since AFAICS that's now going to proceed from where it would have errored out before, with a count of -2. I think it might be nicer to implement this by passing an extra "assume zero if #cells not found" boolean to __of_parse_phandle_with_args(). Alternatively, what's the actual likelihood of legacy bindings being mixed in with new ones? Could we not simply mandate that anyone adding an MSI controller with #msi-cells to a DT must ensure any existing nodes are also updated with #msi-cells = 0, and keep the legacy workaround self-contained in the MSI layer? e.g. paraphrasing from patch 2/2: msi_np = of_parse_phandle(np, "msi-parent", 0); if (!of_property_read_bool(msi_np, "#msi-cells")) return parse_this_thing(...); else while (!of_parse_phandle_with_opt_args(np, "msi-parent"... if (parse_this_thing(...)) return; Robin. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754222AbbI3Pjk (ORCPT ); Wed, 30 Sep 2015 11:39:40 -0400 Received: from eu-smtp-delivery-143.mimecast.com ([207.82.80.143]:57994 "EHLO eu-smtp-delivery-143.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754096AbbI3Pji convert rfc822-to-8bit (ORCPT ); Wed, 30 Sep 2015 11:39:38 -0400 Subject: Re: [PATCH 1/4] of: Add of_parse_phandle_with_opt_args() helper function To: Marc Zyngier , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" References: <1442944336-11754-1-git-send-email-marc.zyngier@arm.com> <1442944336-11754-2-git-send-email-marc.zyngier@arm.com> Cc: Mark Rutland , Bjorn Helgaas , Thomas Gleixner , Rob Herring , Jason Cooper From: Robin Murphy Message-ID: <560C0232.2010100@arm.com> Date: Wed, 30 Sep 2015 16:39:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <1442944336-11754-2-git-send-email-marc.zyngier@arm.com> X-OriginalArrivalTime: 30 Sep 2015 15:39:30.0697 (UTC) FILETIME=[32A33F90:01D0FB96] X-MC-Unique: tjU6-xPdSXy6gkfARJTc_w-1 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Marc, On 22/09/15 18:52, Marc Zyngier wrote: > of_parse_phandle_with_args() is slightly inflexible as it doesn't > allow the (unusual) case where the #*-cells property is not defined. > In order to support this, introduce of_parse_phandle_with_opt_args() > which assumes that #*-cells is zero when it is not defined, > as required by the msi-parent binding > > This is done by turning __of_parse_phandle_with_args into an even > bigger monster, which is a bit frightening. A monster indeed; I can't quite figure out the exact effect this change has on of_count_phandle_with_args(), but I have a lingering doubt it may be something undesirable, since AFAICS that's now going to proceed from where it would have errored out before, with a count of -2. I think it might be nicer to implement this by passing an extra "assume zero if #cells not found" boolean to __of_parse_phandle_with_args(). Alternatively, what's the actual likelihood of legacy bindings being mixed in with new ones? Could we not simply mandate that anyone adding an MSI controller with #msi-cells to a DT must ensure any existing nodes are also updated with #msi-cells = 0, and keep the legacy workaround self-contained in the MSI layer? e.g. paraphrasing from patch 2/2: msi_np = of_parse_phandle(np, "msi-parent", 0); if (!of_property_read_bool(msi_np, "#msi-cells")) return parse_this_thing(...); else while (!of_parse_phandle_with_opt_args(np, "msi-parent"... if (parse_this_thing(...)) return; Robin.