From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4EB05C433E2 for ; Mon, 29 Mar 2021 10:10:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2AA9460230 for ; Mon, 29 Mar 2021 10:10:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232070AbhC2KJe convert rfc822-to-8bit (ORCPT ); Mon, 29 Mar 2021 06:09:34 -0400 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]:22682 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232473AbhC2KJZ (ORCPT ); Mon, 29 Mar 2021 06:09:25 -0400 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-88-4yJ4TLFFOSu6qY5lPx_EXg-1; Mon, 29 Mar 2021 11:09:14 +0100 X-MC-Unique: 4yJ4TLFFOSu6qY5lPx_EXg-1 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) by AcuMS.aculab.com (fd9f:af1c:a25b:0:994c:f5c2:35d6:9b65) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 29 Mar 2021 11:09:13 +0100 Received: from AcuMS.Aculab.com ([fe80::994c:f5c2:35d6:9b65]) by AcuMS.aculab.com ([fe80::994c:f5c2:35d6:9b65%12]) with mapi id 15.00.1497.012; Mon, 29 Mar 2021 11:09:13 +0100 From: David Laight To: 'Xiaofei Tan' , "rjw@rjwysocki.net" , "lenb@kernel.org" , "rui.zhang@intel.com" , "bhelgaas@google.com" CC: "linux-acpi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linuxarm@openeuler.org" Subject: RE: [PATCH v2 04/15] ACPI: table: replace __attribute__((packed)) by __packed Thread-Topic: [PATCH v2 04/15] ACPI: table: replace __attribute__((packed)) by __packed Thread-Index: AQHXIt3reusKxfb1K0qiX/864DlgraqavWWQ Date: Mon, 29 Mar 2021 10:09:13 +0000 Message-ID: <6df04be78e544e17b3b57f159312541f@AcuMS.aculab.com> References: <1616831193-17920-1-git-send-email-tanxiaofei@huawei.com> <1616831193-17920-5-git-send-email-tanxiaofei@huawei.com> In-Reply-To: <1616831193-17920-5-git-send-email-tanxiaofei@huawei.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=C51A453 smtp.mailfrom=david.laight@aculab.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org From: Xiaofei Tan > Sent: 27 March 2021 07:46 > > Replace __attribute__((packed)) by __packed following the > advice of checkpatch.pl. > > Signed-off-by: Xiaofei Tan > --- > drivers/acpi/acpi_fpdt.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/acpi/acpi_fpdt.c b/drivers/acpi/acpi_fpdt.c > index a89a806..690a88a 100644 > --- a/drivers/acpi/acpi_fpdt.c > +++ b/drivers/acpi/acpi_fpdt.c > @@ -53,7 +53,7 @@ struct resume_performance_record { > u32 resume_count; > u64 resume_prev; > u64 resume_avg; > -} __attribute__((packed)); > +} __packed; > > struct boot_performance_record { > struct fpdt_record_header header; > @@ -63,13 +63,13 @@ struct boot_performance_record { > u64 bootloader_launch; > u64 exitbootservice_start; > u64 exitbootservice_end; > -} __attribute__((packed)); > +} __packed; > > struct suspend_performance_record { > struct fpdt_record_header header; > u64 suspend_start; > u64 suspend_end; > -} __attribute__((packed)); > +} __packed; My standard question about 'packed' is whether it is actually needed. It should only be used if the structures might be misaligned in memory. If the only problem is that a 64bit item needs to be 32bit aligned then a suitable type should be used for those specific fields. Those all look very dubious - the standard header isn't packed so everything must eb assumed to be at least 32bit aligned. There are also other sub-structures that contain 64bit values. These don't contain padding - but that requires 64bit alignement. The only problematic structure is the last one - which would have a 32bit pad after the header. Is this even right given than there are explicit alignment pads in some of the other structures. If 64bit alignment isn't guaranteed then a '64bit aligned to 32bit' type should be used for the u64 fields. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)