Re: Issues with USB-C external monitors

On 01.12.2020 17:10, myfreeweb wrote:
> devd (really drm in the kernel) provides hotplug events (system DRM, type HOTPLUG).
> libudev-devd translates these to UD_ACTION_HOTPLUG.
> This works well with wlroots compositors at least.
> How xorg does this I have no idea, as I don't use xorg.
> If your xorg is built with DEVD instead of UDEV option, it shouldn't work, I don't recall anyone adding support for that there.
> With UDEV it might work?

Actually Xorg on FreeBSD with UDEV is compiled with
--disable-config-udev-kms, thus the server never calls:

udev_monitor_filter_add_match_subsystem_devtype

for GPU devices, and thus libudev-devd doesn't forward kms events to the
server. Actually Xorg doesn't even process them, even if the filter check
is bypassed in libudev-devd (udev-monitor.c:261).

Basically Xorg is missing bsd platform code for drm devices, on Linux
the code that implements that can be found in:
hw/xfree86/os-support/linux/lnx_platform.c

Compiling the server with --enable-config-udev-kms, the server expects
to have the following functions implemented

xf86PlatformReprobeDevice, xf86PlatformDeviceProbe, DeleteGPUDeviceRequest and
xf86PlatformDeviceCheckBusID.

Those are fairly easy to implement to enable Xorg to listen to
libudev-devd drm events and to re-configure the drm connectors. I have
already some scratch code, will test more and probably send upstream.

I will probably also add devd code for that, as I use xorg server
with devd on my FreeBSD 12.x machines.

Thanks,
Ali