From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [RFC PATCH v7 6/9] media: tegra: Add Tegra210 Video input driver Date: Wed, 15 Apr 2020 09:54:35 -0700 Message-ID: References: <1586919463-30542-1-git-send-email-skomatineni@nvidia.com> <1586919463-30542-7-git-send-email-skomatineni@nvidia.com> <4118112f-f865-5460-6319-d71271fd78d1@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <4118112f-f865-5460-6319-d71271fd78d1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> Content-Language: en-US Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dmitry Osipenko , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, frankc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, sakari.ailus-X3B1VOXEql0@public.gmane.org, helen.koike-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org Cc: sboyd-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 4/15/20 7:22 AM, Dmitry Osipenko wrote: > External email: Use caution opening links or attachments > > > 15.04.2020 05:57, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> +static int tegra_csi_remove(struct platform_device *pdev) >> +{ >> + struct tegra_csi *csi =3D platform_get_drvdata(pdev); >> + int err; >> + >> + err =3D host1x_client_unregister(&csi->client); >> + if (err < 0) { >> + dev_err(csi->dev, >> + "failed to unregister host1x client: %d\n", err); >> + return err; >> + } >> + >> + pm_runtime_disable(csi->dev); >> + kfree(csi); > IIRC, the driver removal is invoked on the unbinding. Hence, I'm not > sure how moving away from the resource-managed API helps here. Could you > please explain in a more details? > > Have you tried to test this driver under KASAN? I suspect that you just > masked the problem, instead of fixing it. Using devm_kzalloc for vi/csi structures based on prior feedback request=20 to switch to use kzalloc all over this driver. Hi Hans, video devices lifetime is till video device nodes are released. So, v4l2=20 device release callback does the release of tegra channel allocation=20 which hold video device. Below are the 3 possible cases of unbind/unload, 1. during tegra-video module unload, if v4l2 device refcnt is not 0=20 which is the case when any of video device node handle is kept opened=20 then unloading module will not happen and module refcnt is also non-zero=20 and unloading tegra-video module reports module in use. 2. during tegra-video driver unbind, tegra-video driver removal will do=20 vi/csi clients exit ops which unregisters video device allocated memory=20 during release callback of v4l2 device. vi/csi structure allocation=20 remains same as vi/csi driver removal will not happen in this case. 3. during direct host1x client drivers vi/csi unbind, both=20 host1x_clients vi/csi gets unregistered, deletes host1x logical device=20 which executes tegra-video driver removal() -> vi/csi exit() before=20 vi/csi memory gets freed in vi/csi driver remove(). So, any active streaming will stop and video devices are unregistered=20 during direct client driver unbind prior to freeing vi/csi memory. Also vi/csi driver remove does explicit free vi/csi as its allocated=20 with kzalloc. So not sure how using kzalloc is different to devm_kzalloc=20 for vi/csi structure in terms of when vi/csi memory gets freed? Except for channel allocation which holds video device and as video=20 device life time is beyond tegra-video module unbind->vi exit(), looks=20 like we can use devm_kzalloc for vi/csi. Can you please comment if you still think we need to use kzalloc rather=20 than devm_kzalloc for vi/csi structure allocation? Thanks Sowjanya