On Fri, Oct 21, 2016 at 02:45:41PM +0200, Daniel Vetter wrote: > On Fri, Oct 21, 2016 at 10:14:21AM +0100, Chris Wilson wrote: > > If we know which connector was plugged/unplugged or > > connected/disconnected, we can pass that information along to userspace > > inside the uevent to reduce the amount of work userspace has to perform > > after the event (i.e. instead of looking over all connectors, it can > > just reprobe the affected one). > > > > v2: Don't convert intel_hotplug.c, it does a light probe and doesn't > > need the force. > > > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > > Cc: Villle Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx> > > Nothing is preventing multiple connectors to change state at the same > time. Or at least almost the same time, e.g. yank an entire dp mst chain. Or from sending multiple uevents in the time it takes userspace to respond. > I think we need something that works per-connector, so either send out > uevents for one that changed individually. Or go with the epoche counter > idea. The later has the upside that it disconnects probing from reporting: > Sometimes only deep down in the driver's probe function do we realize that > something changed (e.g. different edid, or different dpcd). With a helper > to increment the epoche there would be no need to wire the hotplug status > through the entire callchain. > > To give us the same speed-up benefits like this here the only thing we'd > need to do is make sure reading a read-only (i.e. not userspace setable > prop) doesn't take any heavyweight locks. That should be easy to achieve. > Of course that leaves us with num_connector ioctl calls, but that should > be acceptable. > > And it's an uabi change either way. This is a very simple extension to the current abi that provides a small additional hint. (And it is purely an optional hint.) I agree it is not as impactful as being able to categorically detect whether or not connector state has changed using an epoch counter, but it can provide a meaningful improvement right now. :) The simplest way to add the epoch would either be an extension to GETCONNECTOR or GETPROPBLOB, as there is no way to query a connector property otherwise (at least not after a cursory double check). getconnector->pad has never been set, so it would require GETCONNECTORv2 (just to add a new 64bit field to the struct, the simplest being a u64 nsec timestamp of last change). A simple extension either way. -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
