Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756912AbcDGQkh (ORCPT ); Thu, 7 Apr 2016 12:40:37 -0400 Received: from mga02.intel.com ([134.134.136.20]:63010 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756453AbcDGQkf (ORCPT ); Thu, 7 Apr 2016 12:40:35 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.24,449,1455004800"; d="scan'208";a="927663683" Message-ID: <1460047286.6620.26.camel@linux.intel.com> Subject: Re: [PATCH v1 06/10] device property: switch to use UUID API From: Andy Shevchenko To: "Rafael J. Wysocki" , Huang Ying Cc: "Theodore Ts'o" , Arnd Bergmann , Greg Kroah-Hartman , Jarkko Sakkinen , Jani Nikula , David Airlie , Benjamin Tissoires , Bjorn Helgaas , Mathias Nyman , Matt Fleming , Lv Zheng , Mark Brown , Zhang Rui , Mika Westerberg , Andrew Morton , Rasmus Villemoes , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-efi@vger.kernel.org, linux-api@vger.kernel.org, linux-nvdimm@ml01.01.org Date: Thu, 07 Apr 2016 19:41:26 +0300 In-Reply-To: <1456495897.13244.144.camel@linux.intel.com> References: <1455711448-124103-1-git-send-email-andriy.shevchenko@linux.intel.com> <1455711448-124103-7-git-send-email-andriy.shevchenko@linux.intel.com> <7544228.v4QPX4F7J7@vostro.rjw.lan> <1456495897.13244.144.camel@linux.intel.com> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.5.1-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 68 On Fri, 2016-02-26 at 16:11 +0200, Andy Shevchenko wrote: > On Thu, 2016-02-18 at 01:03 +0100, Rafael J. Wysocki wrote: > > > > On Wednesday, February 17, 2016 02:17:24 PM Andy Shevchenko wrote: > > > > > > Switch to use a generic UUID API instead of custom approach. It > > > allows to > > > define UUIDs, compare them, and validate. > [] > Summon initial author of the UUID library. Summary: the API of comparison functions is rather strange. What the point to not take pointers directly? (Moreover I hope compiler too clever not to make a copy of constant arguments there) I could only imagine the case you are trying to avoid temporary variables for constants like NULL_UUID. Issue with this is the ugliness in the users of that, in particularly present in ACPI (drivers/acpi/apei/ghes.c). I would like to have more clear interface for that. Perhaps we may add something like cmp_p(pointer, non-pointer); cmp_pp(pointer, pointer); to not break existing API for now. It would be useful for many cases in the kernel. > > > > > > > > +static const uuid_le ads_uuid = > > > + UUID_LE(0xdbb8e3e6, 0x5886, 0x4ba6, > > > + 0x87, 0x95, 0x13, 0x19, 0xf5, 0x2a, 0x96, 0x6b); > > >   > > >  static bool acpi_enumerate_nondev_subnodes(acpi_handle scope, > > >      const union > > > acpi_object > > > *desc, > > > @@ -138,7 +136,7 @@ static bool > > > acpi_enumerate_nondev_subnodes(acpi_handle scope, > > >       || links->type != ACPI_TYPE_PACKAGE) > > >   break; > > >   > > > - if (memcmp(uuid->buffer.pointer, ads_uuid, > > > sizeof(ads_uuid))) > > > + if (uuid_le_cmp(*(uuid_le *)uuid->buffer.pointer, > > > ads_uuid)) > > Maybe it's too late, but I don't quite understand the pointer > > manipulations here. > > > > I can see why you need a type conversion (although it looks ugly), > > but why do you > > need to dereference it too? > The function takes that kind of type on input. The other variants are > not compiled. > Perhaps we better change uuid_{lb}e_cmp() first to take normal > pointers, though I think the initial idea was to get type checking at > compile time. > -- Andy Shevchenko Intel Finland Oy