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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id o18sm1360571lfb.13.2020.04.06.09.11.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Apr 2020 09:11:31 -0700 (PDT) Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, frankc@nvidia.com, hverkuil@xs4all.nl, sakari.ailus@iki.fi, helen.koike@collabora.com Cc: sboyd@kernel.org, linux-media@vger.kernel.org, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> <40102767-ecdb-e958-66f4-45d11464069c@gmail.com> From: Dmitry Osipenko Message-ID: <6014fee9-ce97-7ced-f2ba-82176b8b36db@gmail.com> Date: Mon, 6 Apr 2020 19:11:30 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 06.04.2020 18:41, Sowjanya Komatineni пишет: > > On 4/5/20 2:11 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 04.04.2020 04:25, Sowjanya Komatineni пишет: >> ... >>> +static int tegra_vi_tpg_channels_alloc(struct tegra_vi *vi) >>> +{ >>> +     struct tegra_vi_channel *chan, *tmp; >>> +     unsigned int port_num; >>> +     unsigned int nchannels = vi->soc->vi_max_channels; >>> +     int ret = 0; >>> + >>> +     for (port_num = 0; port_num < nchannels; port_num++) { >>> +             /* >>> +              * Do not use devm_kzalloc as memory is freed immediately >>> +              * when device instance is unbound but application >>> might still >>> +              * be holding the device node open. Channel memory >>> allocated >>> +              * with kzalloc is freed during video device release >>> callback. >>> +              */ >>> +             chan = kzalloc(sizeof(*chan), GFP_KERNEL); >> Why anyone would want to unbind this driver in practice? >> >> I think it should make more sense to set suppress_bind_attrs=true. > > From the previous feedback of patch series, we need to support > unbind/bind and looks like this driver should also support to built as a > module. If module unloading is also affected, then perhaps you should use get/put_device() to not allow freeing the resources until they're still in-use. I suppose that it should be up to the V4L core to keep the device alive while needed, rather than to put the burden to the individual drivers.