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[216.228.112.22]) by smtp.gmail.com with ESMTPSA id n9sm822737pgi.2.2020.09.29.23.19.24 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Sep 2020 23:19:24 -0700 (PDT) Date: Tue, 29 Sep 2020 23:13:52 -0700 From: Nicolin Chen To: Dmitry Osipenko Cc: thierry.reding@gmail.com, joro@8bytes.org, krzk@kernel.org, vdumpa@nvidia.com, jonathanh@nvidia.com, linux-tegra@vger.kernel.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/3] iommu/tegra-smmu: Rework .probe_device and .attach_dev Message-ID: <20200930061351.GA16460@Asurada-Nvidia> References: <20200930003013.31289-1-nicoleotsuka@gmail.com> <20200930003013.31289-3-nicoleotsuka@gmail.com> <75514da5-e63a-9e51-8376-abbd12c324d1@gmail.com> <20200930054900.GG31821@Asurada-Nvidia> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-tegra@vger.kernel.org On Wed, Sep 30, 2020 at 09:10:38AM +0300, Dmitry Osipenko wrote: > 30.09.2020 08:49, Nicolin Chen пишет: > > On Wed, Sep 30, 2020 at 08:11:52AM +0300, Dmitry Osipenko wrote: > >> 30.09.2020 03:30, Nicolin Chen пишет: > >>> + /* An invalid mc pointer means mc and smmu drivers are not ready */ > >>> + if (IS_ERR_OR_NULL(mc)) > >> > >> tegra_get_memory_controller() doesn't return NULL. > > > > Well, I don't want to assume that it'd do that forever, and the > > NULL check of IS_ERR_OR_NULL is marked "unlikely" so it doesn't > > hurt to have. > > > > I don't see any reasons why it won't do that forever. > > Secondly, public function can't be changed randomly without updating all > the callers. > > Hence there is no need to handle cases that can't ever happen and it > hurts readability of the code + original error code is missed. I don't quite understand why an extra "_OR_NULL" would hurt readability....but I'd take a step back and use IS_ERR().