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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URI_HEX,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 457B3C11D1B for ; Thu, 20 Feb 2020 19:11:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 217A12465D for ; Thu, 20 Feb 2020 19:11:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="lwip480+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728336AbgBTTLo (ORCPT ); Thu, 20 Feb 2020 14:11:44 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:2123 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728111AbgBTTLo (ORCPT ); Thu, 20 Feb 2020 14:11:44 -0500 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 20 Feb 2020 11:10:31 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Thu, 20 Feb 2020 11:11:43 -0800 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Thu, 20 Feb 2020 11:11:43 -0800 Received: from [10.2.163.58] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 20 Feb 2020 19:11:42 +0000 Subject: Re: [RFC PATCH v3 4/6] media: tegra: Add Tegra210 Video input driver To: Hans Verkuil , , , , , CC: , , , , References: <1581704608-31219-1-git-send-email-skomatineni@nvidia.com> <1581704608-31219-5-git-send-email-skomatineni@nvidia.com> From: Sowjanya Komatineni Message-ID: Date: Thu, 20 Feb 2020 11:11:51 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1582225831; bh=heGfCD1XOLpMxJxA4HNefg5duZSK5mV5RMUR+iVA1L8=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=lwip480+6jSOA6Li0cjyn37svqwAVWkRifwsZL3qphkMWbEa9Eai7Gb4N63teRGCF dalP/2lfjPUeLWOacg1RW2PzPGQSKZTEa0xdPBk0cYEjki/3guB9cGhywQoF1bd5MF RsDsMX7y9ZHfsjdiXomO8iurvuGuh/3XukmWJB/KNrHDhDCkWklTYNEv0yE+u7OEU8 D9hygg5Ujtm1CDQERG0fjfinHhdDk5zPeYIJB0HsQPLvMmhvWAglWQYUFsKNoRMVPW 3NQh+XpBhvjdcNwUa9mtwmRb9GkXAwGzp0XUbe/mOabrq/LL9HsbWixuMvMNbVQiqP iCKn80t/DrJvw== Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 2/20/20 5:33 AM, Hans Verkuil wrote: > External email: Use caution opening links or attachments > > > (Replying to myself so I can explain this a bit more) > > On 2/20/20 1:44 PM, Hans Verkuil wrote: >>> + >>> +static int tegra_csi_tpg_channels_alloc(struct tegra_csi *csi) >>> +{ >>> + struct device_node *node = csi->dev->of_node; >>> + unsigned int port_num; >>> + int ret; >>> + struct tegra_csi_channel *item; >>> + unsigned int tpg_channels = csi->soc->csi_max_channels; >>> + >>> + /* allocate CSI channel for each CSI x2 ports */ >>> + for (port_num = 0; port_num < tpg_channels; port_num++) { >>> + item = devm_kzalloc(csi->dev, sizeof(*item), GFP_KERNEL); >> Using devm_*alloc can be dangerous. If someone unbinds the driver, then >> all memory allocated with devm_ is immediately freed. But if an application >> still has a filehandle open, then when it closes it it might still reference >> this already-freed memory. >> >> I recommend that you avoid using devm_*alloc for media drivers. > A good test is to unbind & bind the driver: > > cd /sys/devices/platform/50000000.host1x/54080000.vi/driver > echo -n 54080000.vi >unbind > echo -n 54080000.vi >bind > > First just do this without the driver being used. That already > gives me 'list_del corruption' kernel messages (list debugging > is turned on in my kernel). > > Note that this first test is basically identical to a rmmod/modprobe > of the driver. But when I compiled the driver as a module it didn't > create any video device nodes! Nor did I see any errors in the kernel > log. I didn't pursue this, and perhaps I did something wrong, but it's > worth taking a look at. > > The next step would be to have a video node open with: > > v4l2-ctl --sleep 10 > > then while it is sleeping unbind the driver and see what happens > when v4l2-ctl exits. > > Worst case is when you are streaming: > > v4l2-ctl --stream-mmap > > and then unbind. > > In general, the best way to get this to work correctly is: > > 1) don't use devm_*alloc > 2) set the release callback of struct v4l2_device and do all freeing there. > 3) in the platform remove() callback you call media_device_unregister() > and video_unregister_device(). Reg 3, in current patch, media_device_unregister is called in host1x_video_remove video_unregister_device happens during host1x_video_remove -> host1x_device_exit -> tegra_vi_exit -> tegra_vi_channels_cleanup > It's worth getting this right in this early stage, rather than fixing it > in the future. > > Regards, > > Hans