On 08.01.2019 12:38, Russell King - ARM Linux wrote: > On Tue, Jan 08, 2019 at 12:25:34PM +0100, Andrzej Hajda wrote: >> Issues with device links have nothing to do with hotplugging, they are >> generic - lifetime of the objects (drm_bridge, drm_panel) is just >> slightly different of lifetime of device links, and this is racy even if >> you do not want hotplugging. Moreover since drm_dev is not device (has >> no associated struct device) assuming we can reuse its parent to create >> device link results in circular dependencies. > How about having the device links created depending on whether the > main drm driver wants them or not - that would mean that Exynos > could continue avoiding them, but others that want them can have > the links? That should be OK for Exynos. But regardless of Exynos device_links at the current state will not work correctly with bridges/panels as I described earlier. > > I don't think the links should be created when the bridge is attached, > they should be created when the main drm driver gains its first > reference to the drm_bridge (via of_drm_find_bridge()) - since that's > the point where things may explode if the drm_bridge goes away. > Calling drm_bridge_attach() for a bridge that has been unbound will > be a use-after-free bug, so using device links at that point is way > too late. > If you want to create device_link you should access bridge->dev, if you do it outside bridge_lock it can explode as well. So link should be created under bridge_lock then (inside of_drm_find_bridge? via another getter? ). Regards Andrzej _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
