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=-6.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 5E82FC433E6 for ; Tue, 26 Jan 2021 12:57:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 303A623109 for ; Tue, 26 Jan 2021 12:57:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391915AbhAZM4n (ORCPT ); Tue, 26 Jan 2021 07:56:43 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42360 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404138AbhAZM4R (ORCPT ); Tue, 26 Jan 2021 07:56:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611665691; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=d/k87fvwAVxIbqpDlDjqYev8POnbfvLdlH/1Fc3eH7k=; b=VWZZ8/Qo37R3/73dMaGgmDiwhZtRXVce3lWkESYcAHLK1pVUCpbEfeju7d32+H1ymwIPyG h2aK3npbdCEjBWArHRYKYhTUZEqJGPTfihDyMntOvdNU1lA+qlOgn9Oh0A4e1CbaNbGJzf QhQCBl/u5jESthhHp9NfRydyb5hV8Pk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-231-sr84HsX9PeyKyHEQrtn-uQ-1; Tue, 26 Jan 2021 07:54:49 -0500 X-MC-Unique: sr84HsX9PeyKyHEQrtn-uQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E9E54801AAC; Tue, 26 Jan 2021 12:54:47 +0000 (UTC) Received: from prarit.bos.redhat.com (prarit-guest.7a2m.lab.eng.bos.redhat.com [10.16.222.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 404805D751; Tue, 26 Jan 2021 12:54:47 +0000 (UTC) From: Prarit Bhargava To: prarit@redhat.com Cc: bhelgaas@google.com, corbet@lwn.net, leon@kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, mstowe@redhat.com Subject: Re: [PATCH] pci-driver: Add driver load messages Date: Tue, 26 Jan 2021 07:54:46 -0500 Message-Id: <20210126125446.1118325-1-prarit@redhat.com> In-Reply-To: <20210126063935.GC1053290@unreal> References: <20210126063935.GC1053290@unreal> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Leon Romanovsky wrote: > On Mon, Jan 25, 2021 at 02:41:38PM -0500, Prarit Bhargava wrote: > > There are two situations where driver load messages are helpful. > > > > 1) Some drivers silently load on devices and debugging driver or system > > failures in these cases is difficult. While some drivers (networking > > for example) may not completely initialize when the PCI driver probe() function > > has returned, it is still useful to have some idea of driver completion. > > Sorry, probably it is me, but I don't understand this use case. > Are you adding global to whole kernel command line boot argument to debug > what and when? > > During boot: > If device success, you will see it in /sys/bus/pci/[drivers|devices]/*. > If device fails, you should get an error from that device (fix the > device to return an error), or something immediately won't work and > you won't see it in sysfs. > What if there is a panic during boot? There's no way to get to sysfs. That's the case where this is helpful. > During run: > We have many other solutions to get debug prints during run, for example > tracing, which is possible to toggle dynamically. > > Right now, my laptop will print 34 prints on boot and endless amount during > day-to-day usage. > > ➜ kernel git:(rdma-next) ✗ lspci |wc -l > 34 > > > > > 2) Storage and Network device vendors have relatively short lives for > > some of their hardware. Some devices may continue to function but are > > problematic due to out-of-date firmware or other issues. Maintaining > > a database of the hardware is out-of-the-question in the kernel as it would > > require constant updating. Outputting a message in the log would allow > > different OSes to determine if the problem hardware was truly supported or not. > > And rely on some dmesg output as a true source of supported/not supported and > making this ABI which needs knob in command line. ? Yes. The console log being saved would work as a true source of load messages to be interpreted by an OS tool. But I see your point about the knob below... > > > > > Add optional driver load messages from the PCI core that indicates which > > driver was loaded, on which slot, and on which device. > > Why don't you add simple pr_debug(..) without any knob? You will be able > to enable/disable it through dynamic prints facility. Good point. I'll wait for more feedback and submit a v2 with pr_debug. P. > > Thanks