Hi All, Somewhat long mail, so I've divided it into "chapters", sorry. 1. Back ground info ------------------- First some quick background, some recent Lenovo models have a builtin privacy screen which can be turned on/off in software and the kernel recently has gotten support for this: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=110ea1d833ad291272d52e0a40a06157a3d9ba17 We have been looking into adding support for this to GNOME, but the userspace API added by the above commit is very Thinkpad specific, and we would rather not rely on an userspace API which is specific to 1 series of laptops. When we started discussing this I had already seen some versions of Rajat's "drm/i915 Support for integrated privacy screen" series: https://patchwork.freedesktop.org/series/74650/ Which adds support for integrated privacy screens as a drm-connector property. Anyone who has been involved in the backlight brightness control saga we have with the sysfs backlight class instantly knows/feels that this is the right way to handle this. So now we want to export the Thinkpad lcdshadow attribute as a drm-connector property. 2. Problem + Possible solutions ------------------------------- The problem is that the code to get/set the lcdshadow setting and also the code to listen for firmware (hardcoded hotkeys) triggered state changes all lives inside the thinkpad_acpi driver; and to export the lcdshadow setting as a drm property we need to access that code (and it is too big to just copy over). One thing which makes this trickier is that all properties must be attached to the connector before it is registered, we cannot add it at a later time. I see 3 possible solutions here: i. Export some symbols from thinkpad_acpi and directly call these from drm_connector_create_standard_properties and other drm_connector functions if the thinkpad_acpi module is enabled. Note this should be done in the core drm_connector functions since the GPU might be one of i915 / amdgpu / nouveau. I believe that it is clear that this solution is not very elegant. A variant of this would be to have a separate helper module (probaly a few static inlines in a .h) which exports some hooks for i915 / amdgpu / nouveau to call this way we at least keep the ugliness out of the core and keep the module-dep on thinkpad_acpi limited to the i915 / amdgpu / nouveau modules. This might actually not be too bad, except that currently the thinkpad_acpi module refuses to load on non thinkpads... ii. Currently the "privacy-screen" property added by Rajat's patch-set is an enum with 2 possible values: "Enabled" "Disabled" We could add a third value "Not Available", which would be the default and then for internal panels always add the property so that we avoid the problem that detecting if the laptop has an internal privacy screen needs to be done before the connector is registered. Then we can add some hooks which allow an lcdshadow-driver to register itself against a connector later (which is non trivial wrt probe order, but lets ignore that for now). iii. We can add a generic framework to allow drivers outside of the drm-subsys to register something drm_property(ish) specifying a dev_name() and connector-name to which to attach the property when that connector gets created on that device. This requires the driver registering this property to be fully loaded before the connector gets registered. 3. Picking a solution --------------------- i. is just ugly, full stop, but also very KISS which still makes it somewhat appealing. Also i. does not scale if we get other vendor specific interfaces for interacting with these privacy screens. ii. is ugly from an userspace API pov, if there is no "privacy-screen" then we really should not have the property at all rather then setting it to "Not Available". Still it might be an acceptable compromise I guess iii. is/was the one I liked, until I started looking at the drm_connector code and saw that all properties must be attached before registering the connector, bummer. Then this morning I remembered that the i915 driver has a similar issue with the gvt stuff / the kvmgt module. The kvmgt module must be loaded and fully initialized before the i915 driver loads. This has been solved with module softdeps. I think that we can do the same here having either the i915+nouveau+amdgpu drivers; or the drm-core have a softdep on thinkpad_acpi so that it can register the lcdshadow property with the to-be-written framework for externally managed props before the internal panels drm-connector gets created. This also allows the thinkpad_acpi module_init function to return -ENODEV on non Thinkpad devices, so that it will not take up memory, where as with i. we would always need to have it in memory. I'm currently leaning towards iii. combined with using MODULE_SOFTDEP("pre: thinkpad_acpi") to make sure the thinkpad_acpi driver can do its thing before the internal display connector gets created. Daniel (and others) does this (iii. + softdeps) sound like something which might be acceptable (I know it will also depend on the resulting code implementing this idea) ? Any other ideas / suggestions are appreciated here. Regards, Hans _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
