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=-4.1 required=3.0 tests=BAYES_00,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 09991C433E1 for ; Wed, 15 Jul 2020 11:50:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D5C782070E for ; Wed, 15 Jul 2020 11:50:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="LgZ4K6Ei" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729304AbgGOLue (ORCPT ); Wed, 15 Jul 2020 07:50:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728413AbgGOLue (ORCPT ); Wed, 15 Jul 2020 07:50:34 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A6260C061755 for ; Wed, 15 Jul 2020 04:50:33 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id c80so5300826wme.0 for ; Wed, 15 Jul 2020 04:50:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to; bh=/T16uCv1ZWPqSW676gNIrYzGrdvCyTZGrAfC73gI1R8=; b=LgZ4K6EitdkgNJmIZnB6nrrkUMdllUVyNI6qfVCTSpEPlnB3ZUp9Es7UAQyhkk2ESX l+H779z95rR+9duhx4AG62Afia97T0hXyQ7Yv77OxoAX91FCWUAGTeA80uF2xLY9c9mA E2gWMQuy3uee9dr3EVtZYxqfw18y/qW4jyrI0EpsycGJpLjqdGVPIv9MCp1m+PYBEgL4 5KPMUq/2Nn3HBz6WeL2Zp7Con55/FYRTZQo1su6tmF9R3pWakLiFpyx5vfgvRc40p55D 01HI+OiRmOJi1hhsdeKRK7c6h30p9nu+D0KPRsoOX4dNKS7iKNT1tuChf5ixMNGUwkgE c1gw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=/T16uCv1ZWPqSW676gNIrYzGrdvCyTZGrAfC73gI1R8=; b=IjyWocGP/3765LNZru8iVLWiIud+ycyrRP+1zjAKW+RR3JeVcDZoa3aJTdf1rYpDmA Cz59//IlRXVwDA5a+SmiGay97AVXPHGLc5795++OWJcaY1yuESj+tytfU5iUBF3O3SXQ 6dEDkdEOT4mjzGjarHmyjYWemRv/rP3TgyuAOHlHYbn86H0/7f5RDWZobClree+pM5VG P5+kHAwMxmEely8K6Y8dmIt7fniDyspaAuluWlk7gm3orAg65vA9ruVMd4OxJ82RO27k MJtjKXav/34cPf4TGiy9nPJxXfFHUMqfQyUdA/OZwq61eTiWHzoxZIDIYrolq0ZLq7ez 2F4w== X-Gm-Message-State: AOAM5301ckCsI+Eo1z9OIpgt+aRdf41PUReXgYEHjhwidbhWNB7Dq4pi Pwn+aDGap2DSGMydetdgx/4ZLg== X-Google-Smtp-Source: ABdhPJzhl1aZdPeNw+p/Oo2fOmsYKXVrisAAtybPKQQFyVqm7NZLat5RzBihKMlAoPur6B+enJR0gg== X-Received: by 2002:a05:600c:2317:: with SMTP id 23mr8624550wmo.72.1594813832408; Wed, 15 Jul 2020 04:50:32 -0700 (PDT) Received: from dell ([2.31.163.61]) by smtp.gmail.com with ESMTPSA id d28sm3710893wrc.50.2020.07.15.04.50.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Jul 2020 04:50:31 -0700 (PDT) Date: Wed, 15 Jul 2020 12:50:29 +0100 From: Lee Jones To: "Rafael J. Wysocki" Cc: Viresh Kumar , "Rafael J. Wysocki" , Linux ARM , Linux Kernel Mailing List , Linux PM , Andy Grover , Paul Diefenbaugh , Dominik Brodowski , Denis Sadykov Subject: Re: [PATCH 09/13] cpufreq: acpi-cpufreq: Remove unused ID structs Message-ID: <20200715115029.GC3165313@dell> References: <20200714145049.2496163-1-lee.jones@linaro.org> <20200714145049.2496163-10-lee.jones@linaro.org> <20200714210340.GJ1398296@dell> <20200715032442.gh2cliiddhv35fdj@vireshk-i7> <20200715032718.2zlo2eurhkpoayya@vireshk-i7> <20200715113433.GB3165313@dell> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Wed, 15 Jul 2020, Rafael J. Wysocki wrote: > On Wed, Jul 15, 2020 at 1:34 PM Lee Jones wrote: > > > > On Wed, 15 Jul 2020, Rafael J. Wysocki wrote: > > > > > On Wed, Jul 15, 2020 at 5:27 AM Viresh Kumar wrote: > > > > > > > > On 15-07-20, 08:54, Viresh Kumar wrote: > > > > > On 14-07-20, 22:03, Lee Jones wrote: > > > > > > On Tue, 14 Jul 2020, Rafael J. Wysocki wrote: > > > > > > > > > > > > > On Tue, Jul 14, 2020 at 4:51 PM Lee Jones wrote: > > > > > > > > > > > > > > > > Can't see them being used anywhere and the compiler doesn't complain > > > > > > > > that they're missing, so ... > > > > > > > > > > > > > > Aren't they needed for automatic module loading in certain configurations? > > > > > > > > > > > > Any idea how that works, or where the code is for that? > > > > > > > > > > The MODULE_DEVICE_TABLE() thingy creates a map of vendor-id, > > > > > product-id that the kernel keeps after boot (and so there is no static > > > > > reference of it for the compiler), later when a device is hotplugged > > > > > into the kernel it refers to the map to find the related driver for it > > > > > and loads it if it isn't already loaded. > > > > > > > > > > This has some of it, search for MODULE_DEVICE_TABLE() in it. > > > > > Documentation/driver-api/usb/hotplug.rst > > > > > > > > And you just need to add __maybe_unused to them to suppress the > > > > warning. > > > > > > Wouldn't that cause the compiler to optimize them away if it doesn't > > > see any users? > > > > It looks like they're only unused when !MODULE, > > OK > > > in which case optimising them away would be the correct thing to do, no? It would be good if someone with a little more knowledge could provide a second opinion though. I would think (hope) that the compiler would be smart enough to see when its actually in use. After all, it is the compiler that places the information into the device table. If that is not the case, then the MODULE_DEVICE_TABLE() magic is broken and will need fixing. Removing boiler-plate is good, but not at the expense of obfuscation. -- Lee Jones [李琼斯] Senior Technical Lead - Developer Services Linaro.org │ Open source software for Arm SoCs Follow Linaro: Facebook | Twitter | Blog