10 gru 2014 17:16 "Russell King - ARM Linux" [off-list ref]
napisał(a):

On Wed, Dec 10, 2014 at 04:48:18PM +0100, Andrzej Hajda wrote:

quoted

3. There are drivers which can work without specific resource, but if
  the resource becomes available/unavailable it can do some additional

stuff.

quoted

  An example of such driver is DRM driver (more precisely

drm_connector) -

quoted

  it can start without attached drm_panel, but if the panel becomes

available it

quoted

  can react by generating HPD event and start using it.

Bad example, and actually incorrect.  DRM connectors are referenced in
userspace by an IDR number, which can be re-used in the case of a
connector appearing, disappearing, and then a different connector
re-appearing.

But it is not about reappearing of drm_connector, it is about reappearing
of drm_panel which is fortunately not a part of drm driver. Connector here
is only consumer of drm_panel which should have possibility to receive
notifications on panel (dis-)appearance.

Regards
Andrzej

DRM really is *not* safe to hotplug like this: DRM is more a card-level
thing, which is why we have the component helpers - which allow us to
merge several devices into one logical card-like device in a generic
manner.

DRM needs a stable picture of the CRTCs, encoders and connectors, which
should _never_ change during the lifetime of the DRM device.  Devices
attached to connectors can be hotplugged, but that's about the limit of
hot-plugging in DRM.

--
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.
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