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   ***: vitoriha has left
   koike: media API question 1: in a topology, if the subdevice node is exposed to userspace as /dev/v4l-subdev0, is the implementation of S_/G_FMT in the whole topology mandatory? Or can /dev/v4l-subdev0 only be exposed to allow userspace to subscribe to an event?
   <br> media API question 2: the sensor is usually a diferent driver from the ISP (this is because the same sensor could be used with different ISPs in theory), what happen if one ISP expects the sensor to expose /dev/v4l-subdevX with S_/G_FMT, but another ISP doesn't?
   pinchartl: <u>koike</u>: from a subdev point of view, whether the get/set format operations are called from userspace or from the ISP driver is irrelevant, subdevices shouldn't see the difference
   <br> the5~ ISP can decide to expose subdev device nodes to userspace by calling v4l2_device_register_subdev_nodes()
   <br> so ISP drivers can decide already
   <br> this however prevents not exposing the set format operation to userspace, but exposing events
   <br> for that use case, Jacopo has posted a patch series that introduces a v4l2_device_register_ro_subdev_nodes()
   <br> the subdev nodes will then be read-only
   <br> you will be able to perform any operation that doesn't change the state of the subdev
   <br> get format, set format(TRY), but not set format(ACTIVE)
   <br> and unless I'm mistaken events are available through ro subdev nodes