On Tue, 15 Feb 2022 at 13:55, Simon Ser <contact@xxxxxxxxxxx> wrote: > > On Tuesday, February 15th, 2022 at 13:04, Emil Velikov <emil.l.velikov@xxxxxxxxx> wrote: > > > Greetings everyone, > > > > Padron for joining in so late o/ > > > > On Tue, 8 Feb 2022 at 08:42, Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx> wrote: > > > > > > drm_dev_register() sets connector->registration_state to > > > DRM_CONNECTOR_REGISTERED and dev->registered to true. If > > > drm_connector_set_panel_orientation() is first called after > > > drm_dev_register(), it will fail several checks and results in following > > > warning. > > > > > > Add a function to create panel orientation property and set default value > > > to UNKNOWN, so drivers can call this function to init the property earlier > > > , and let the panel set the real value later. > > > > > > > The warning illustrates a genuine race condition, where userspace will > > read the old/invalid property value/state. So this patch masks away > > the WARNING without addressing the actual issue. > > Instead can we fix the respective drivers, so that no properties are > > created after drm_dev_register()? > > > > Longer version: > > As we look into drm_dev_register() it's in charge of creating the > > dev/sysfs nodes (et al). Note that connectors cannot disappear at > > runtime. > > For panel orientation, we are creating an immutable connector > > properly, meaning that as soon as drm_dev_register() is called we must > > ensure that the property is available (if applicable) and set to the > > correct value. > > Unfortunately we can't quite do this. To apply the panel orientation quirks we > need to grab the EDID of the eDP connector, and this happened too late in my > testing. > > What we can do is create the prop early during module load, and update it when > we read the EDID (at the place where we create it right now). User-space will > receive a hotplug event after the EDID is read, so will be able to pick up the > new value if any. Didn't quite get that, are you saying that a GETPROPERTY for the EDID, the ioctl blocks or that we get an empty EDID? The EDID hotplug even thing is neat - sounds like it also signals on panel orientation, correct? On such an event, which properties userspace should be re-fetching - everything or guess randomly? Looking through the documentation, I cannot see a clear answer :-\ Thanks Emil
