[PATCH 13/64] drm/vc4: hvs: Protect device resources after removal

[Maxime Ripard]

Hi Dave,

On Tue, Jun 14, 2022 at 04:11:20PM +0100, Dave Stevenson wrote:
> On Fri, 10 Jun 2022 at 10:30, Maxime Ripard <maxime at cerno.tech> wrote:
> >
> > Whenever the device and driver are unbound, the main device and all the
> > subdevices will be removed by calling their unbind() method.
> >
> > However, the DRM device itself will only be freed when the last user will
> > have closed it.
> >
> > It means that there is a time window where the device and its resources
> > aren't there anymore, but the userspace can still call into our driver.
> >
> > Fortunately, the DRM framework provides the drm_dev_enter() and
> > drm_dev_exit() functions to make sure our underlying device is still there
> > for the section protected by those calls. Let's add them to the HVS driver.
> 
> The framework appears to rely on the remove function calling
> drm_dev_unplug instead of drm_dev_unregister, but I haven't seen a
> patch that makes that change in the vc4 driver.
> Have I missed it, or is there some other route to set the unplugged
> flag that drm_dev_enter/exit are relying on?

You're right, we should have called drm_dev_unplug. I fixed it up (and
the fallouts)

Thanks!
Maxime
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