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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 6EDCFC432C0 for ; Mon, 18 Nov 2019 18:15:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 484FA222A4 for ; Mon, 18 Nov 2019 18:15:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726427AbfKRSPp (ORCPT ); Mon, 18 Nov 2019 13:15:45 -0500 Received: from foss.arm.com ([217.140.110.172]:38290 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726216AbfKRSPp (ORCPT ); Mon, 18 Nov 2019 13:15:45 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C48A41FB; Mon, 18 Nov 2019 10:15:44 -0800 (PST) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 49A283F703; Mon, 18 Nov 2019 10:15:43 -0800 (PST) Date: Mon, 18 Nov 2019 18:15:38 +0000 From: Lorenzo Pieralisi To: Bjorn Helgaas Cc: Mark Brown , Robin Murphy , shawn.lin@rock-chips.com, andrew.murray@arm.com, heiko@sntech.de, lgirdwood@gmail.com, linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 2/2] PCI: rockchip: Simplify optional regulator handling Message-ID: <20191118181538.GA2261@e121166-lin.cambridge.arm.com> References: <20191118115930.GC9761@sirena.org.uk> <20191118142428.GA27459@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191118142428.GA27459@google.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Nov 18, 2019 at 08:24:28AM -0600, Bjorn Helgaas wrote: > On Mon, Nov 18, 2019 at 11:59:30AM +0000, Mark Brown wrote: > > On Sat, Nov 16, 2019 at 12:54:20PM +0000, Robin Murphy wrote: > > > Null checks are both cheaper and more readable than having !IS_ERR() > > > splattered everywhere. > > > > > - if (IS_ERR(rockchip->vpcie3v3)) > > > + if (!rockchip->vpcie3v3) > > > return; > > > > > > /* > > > @@ -611,6 +611,7 @@ static int rockchip_pcie_parse_host_dt(struct rockchip_pcie *rockchip) > > > if (PTR_ERR(rockchip->vpcie12v) != -ENODEV) > > > return PTR_ERR(rockchip->vpcie12v); > > > dev_info(dev, "no vpcie12v regulator found\n"); > > > + rockchip->vpcie12v = NULL; > > > > According to the API NULL is a valid regulator. We don't currently > > actually do this but it's storing up surprises if you treat it as > > invalid. > > I don't know anything about the regulator API, but the fact that NULL > can be a valid regulator is itself a little surprising :) if (rockchip->vpcie3v3 == NULL) is true the driver would currently panic the kernel AFAICS. rockchip_pcie_set_power_limit() ->regulator_get_current_limit(NULL) -> _regulator_get_current_limit(NULL) -> regulator_lock(NULL) -> regulator_lock_nested(NULL, NULL) -> ww_mutex_trylock(&NULL->mutex) Also, by making NULL a valid regulator, it means that regulators (ie pointers) with default values are valid whether we call devm_regulator_get* or not. I understand this patch can be dropped but that per-se does not make this driver code any more robust AFAICS. Lorenzo