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

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On 4/6/20 9:11 AM, Dmitry Osipenko wrote:
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06.04.2020 18:41, Sowjanya Komatineni пишет:
On 4/5/20 2:11 PM, Dmitry Osipenko wrote:
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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.

Hans/Thierry, Can you please comment on this?





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