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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E4E05EB64DD for ; Wed, 9 Aug 2023 06:31:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230261AbjHIGbO (ORCPT ); Wed, 9 Aug 2023 02:31:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230018AbjHIGbN (ORCPT ); Wed, 9 Aug 2023 02:31:13 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 17ACB10DC for ; Tue, 8 Aug 2023 23:31:12 -0700 (PDT) Received: from canpemm500009.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4RLKsy1hLWzmV69; Wed, 9 Aug 2023 14:29:58 +0800 (CST) Received: from [10.67.102.169] (10.67.102.169) by canpemm500009.china.huawei.com (7.192.105.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Wed, 9 Aug 2023 14:31:09 +0800 CC: , , , , , , Subject: Re: [PATCH] perf/smmuv3: Add platform id table for module auto loading To: Barry Song <21cnbao@gmail.com>, Liang Li References: <20230807122233.28563-1-yangyicong@huawei.com> From: Yicong Yang Message-ID: <23fe3d9a-cb4d-3479-0581-eefec193bc72@huawei.com> Date: Wed, 9 Aug 2023 14:31:09 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.102.169] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500009.china.huawei.com (7.192.105.203) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Barry, Liang, On 2023/8/9 13:47, Barry Song wrote: > On Wed, Aug 9, 2023 at 1:01 PM Liang Li wrote: >> >> On 2023-08-07 20:22, Yicong Yang wrote: >>> From: Yicong Yang >>> >>> On ACPI based system the device is probed by the name directly. If the >>> driver is configured as module it can only be loaded manually. Add the >>> platform id table as well as the module alias then the driver will be >>> loaded automatically by the udev or others once the device added. >>> >> >> Please consider revise the long log to clearly express the purpose of the >> changes in this patch: >> >> - What's the exact issue the patch is addressing >> - Why the changes in this patch can fix the issue or make something working >> - Consider impact of the changes introduced by this patch >> >> These info may help reviewers and maintainers .. and yourself on code merge. > > years ago, i found a good doc regarding this, > https://wiki.archlinux.org/title/Modalias > > guess it is because /lib/modules/$(uname -r)/modules.alias fails to contain smmu > driver without the MODULE_DEVICE_TABLE, isn't it, yicong？ Yes I think it's the reason. I didn't find summary in kernel docs for the modalias as well as the uevent mechanism. Arch wiki has a well illustration for the modalias and suse[1] describes how this is used by the udev for module auto loading. For my case I'm using a ACPI based arm64 server and after booting the arm_smmuv3_pmu.ko is not auto loaded by the udevd since we aren't providing this information. In order to support this we need to provide this MODULE_DEVICE_TABLE() when the smmu pmu added as a platform device, then the userspace udev can know which module to load after the device is added. [1] https://documentation.suse.com/sles/15-SP1/html/SLES-all/cha-udev.html#sec-udev-drivers Thanks.