Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

[Sowjanya Komatineni]

On 4/6/20 9:11 AM, Dmitry Osipenko wrote:
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>
> 06.04.2020 18:41, Sowjanya Komatineni ÐÐÑÐÑ:
> > 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 ÐÐÑÐÑ:
> > > ...
> > > > +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.

Hans/Thierry, Can you please comment on this?