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[91.79.175.49]) by smtp.googlemail.com with ESMTPSA id l3-v6sm2360064ljg.21.2019.02.03.08.42.17 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 03 Feb 2019 08:42:17 -0800 (PST) Subject: Re: [PATCH V9 3/5] i2c: tegra: Add DMA support To: Sowjanya Komatineni , "thierry.reding@gmail.com" , Jonathan Hunter , Mantravadi Karthik , Shardar Mohammed , Timo Alho Cc: "linux-tegra@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-i2c@vger.kernel.org" References: <1549040867-18149-1-git-send-email-skomatineni@nvidia.com> <1549040867-18149-3-git-send-email-skomatineni@nvidia.com> <951cf1f5-ba3a-94ef-0399-2259effebc99@gmail.com> <6150de70-6ca8-944a-780a-4574ff2b21c7@gmail.com> From: Dmitry Osipenko Message-ID: Date: Sun, 3 Feb 2019 19:42:16 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 02.02.2019 21:43, Sowjanya Komatineni пишет: > >>>>>> +static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev) { >>>>>> + struct dma_chan *dma_chan; >>>>>> + u32 *dma_buf; >>>>>> + dma_addr_t dma_phys; >>>>>> + int err = 0; >>>>>> + >>>>>> + if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) >>>>>> + return -ENODEV; >>>>> >>>>> Driver shall not fail to probe if DMA driver is disabled, but to continue with the PIO-only mode available. >>>>> >>>>> Should be: >>>>> >>>>> if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) >>>>> return 0; >>>>> >>>> Except EPROBE_DEFER, anything else returned from tegra_i2c_init_dma >>>> (ENODEV/ENOMEM) is ignored in i2c_probe DMA mode decision is based on xfer size and availability of dma channel or can be changed based on valid dma buf to shorten the line. >>>> >>> >>> Ah, sorry. I missed that, seems good then. >>> >> >> BTW, it may be worthwhile to move out the error code handling into tegra_i2c_init_dma() for clarity. It also won't hurt to not ignore errors other than -ENODEV. > > Either ways are same. To be more readable/clear on error types for diff cases and errors that we are ignoring, I am explicitly keeping error codecs (EPROBE_DEFER/ENODEV/ENOMEM) same way. > Also in probe for readability checking with EPROBE_DEFER which explicitly indicating we keep deferring i2c probe rather than simple return. > Okay, then please add a error message for the dma_chan request-failure, printing a message that tells error code for the case (or even regardless) of errno != -ENODEV.