In order to make it possible to e.g. unload an unused DRM device, we
need to make sure that we don't keep the file descriptor open if we
don't need it; otherwise we block anyone from unloading the
corresponding module.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1828>
Tags are meant to make it possible for a device file opener to tag a
file if it has affected the state the file descriptor is in; e.g. if it
has enabled a DRM capability.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1828>
This practically does the same thing as part of MetaLauncher, except
with added thread safety and caching. For example, opening the same file
a second time will return the same MetaDeviceFile, and only once all
acquired MetaDeviceFile's are released, will the file descriptor be
closed and control of the device released.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1828>
