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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 6BF17C2D0C2 for ; Fri, 3 Jan 2020 14:46:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2AB8F21835 for ; Fri, 3 Jan 2020 14:46:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="OL7BdYVs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727904AbgACOqm (ORCPT ); Fri, 3 Jan 2020 09:46:42 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:60574 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725890AbgACOqm (ORCPT ); Fri, 3 Jan 2020 09:46:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Transfer-Encoding :Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=dxGlP6E/0HnbmMgn1yCwGjBQHVH0nxVSC6z7ysmlKDs=; b=OL7BdYVsmhrEZ6PqewWXvrrH/b EiWzXJN80gQf8xZL1AGC7lanLRcuhef2luI/P0Bp1QDWo4gTSMcnyQSnYTJ+lUGtaBpRvpAeGPWXs Gue5FGGBUKoLkMAR1ShHf0hyKuREbHBeI5zr5WfMZWWVWXpq818HrvNWl3vjW75kcGrwW2Pix6emS DGJRxyiDxDx09lAFEEO+9TRFUUMzGlWl14DDUI6eVLPYMttzrNHspsBmplwjzdwdnRl7Tz/nystz5 EMRDpQn/0LfqNFI6QbcABSG2tkdfI2OuOJG+9QemWA3sm1msZxij2u23XGtYpanGu6NRuj3Zn/aFt zD/4hdjA==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1inODX-0005ig-Sz; Fri, 03 Jan 2020 14:46:23 +0000 Date: Fri, 3 Jan 2020 06:46:23 -0800 From: Matthew Wilcox To: yu kuai Cc: klassert@kernel.org, davem@davemloft.net, hkallweit1@gmail.com, jakub.kicinski@netronome.com, hslester96@gmail.com, mst@redhat.com, yang.wei9@zte.com.cn, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, zhengbin13@huawei.com Subject: Re: [PATCH] net: 3com: 3c59x: remove set but not used variable 'mii_reg1' Message-ID: <20200103144623.GI6788@bombadil.infradead.org> References: <20200103121907.5769-1-yukuai3@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200103121907.5769-1-yukuai3@huawei.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 03, 2020 at 08:19:07PM +0800, yu kuai wrote: > Fixes gcc '-Wunused-but-set-variable' warning: > > drivers/net/ethernet/3com/3c59x.c: In function ‘vortex_up’: > drivers/net/ethernet/3com/3c59x.c:1551:9: warning: variable > ‘mii_reg1’ set but not used [-Wunused-but-set-variable] > > It is never used, and so can be removed. ... > if (dev->if_port == XCVR_MII || dev->if_port == XCVR_NWAY) { > - mii_reg1 = mdio_read(dev, vp->phys[0], MII_BMSR); > mii_reg5 = mdio_read(dev, vp->phys[0], MII_LPA); I know nothing about the MII interface, but in general this is not a safe thing to do. You're removing a read from a device register. Register reads can have side effects. I'm actually quite surprised that GCC emits this warning, since there should be some kind of volatile cast in mdio_read() to let GCC know that something unusual is going on here.