This moves the magic incantation into libdrm and is clearer. See
[1] for details.
While at it, fixup the doc comment and improve logging.
[1]: 523b3658aa
libseat provides all session functionality, so there is no longer need
for a session backend abstraction. The libseat device ID, seat handle
and event loop handle are moved to the main wlr_session and wlr_device
structs.
This allows libseat to be compiled as a Meson subproject when it's
not installed system-wide. This can ease development and compilation
on distributions where libseat isn't packaged.
Sometimes wlr_session_find_gpus will encounter an error. This is
different from finding zero GPUs.
On error, wlr_session_find_gpus already returns -1. However, this is
casted to size_t, so callers uncorrectly assume this is a success.
Instead, make wlr_session_find_gpus return a ssize_t and allow callers
to handle the error accordingly.
Wait for a DRM device if none is found in wlr_session_find_gpus. This
can happen if the compositor is loaded before the display kernel driver.
This supersedes the logind CanGraphical property.
To test, e.g. with i915 and sway:
rmmod -f i915
sway &
modprobe i915
Closes: https://github.com/swaywm/wlroots/issues/2093
We're only interested in card devices. The loop over wlr_session.devices
would take care of ignoring non-card events, but a future patch will
listen to udev "add" events as well.
Instead of operating on FDs in {open,close}_device, operate on
wlr_devices. This avoids the device lookup in wlr_session and allows
callers to have access to wlr_device fields.
For now, we use it to remove wlr_session_signal_add and replace it with
a more idiomatic wlr_session.events.change field. In the future, other
events will be added.
When starting a compositor that's using the "direct" session backend,
wlroots needs to handle calls to `drmSetMaster()` and `drmDropMaster()`.
As both calls used to require `CAP_SYS_ADMIN`, wlroots thus simply
refused starting in case the process doesn't enjoy evelated privileges.
Permission rules have changed since linux.git commit 45bc3d26c95a (drm:
rework SET_MASTER and DROP_MASTER perm handling, 2020-03-19). As a
result, starting with Linux v5.8, both ioctls will now also succeed if
the process is currently or has been the DRM master. And as the first
process to open render nodes will become the DRM master automatically,
this effectively means that process elevation is not strictly required
in all setups anymore.
So let's drop the `geteuid() != 0` permission check to allow those new
rules to do their magic.
bad1e9afa8 ("session: Add libseat backend") introduced a change to to
how session backends initialize, but failed to update the FreeBSD
specific version of the direct backend accordingly.
Closes: https://github.com/swaywm/wlroots/issues/2376
This is simply a false sense of security, and is worse than just using
setuid. CAP_SYS_ADMIN is an extremely serious capability that is
effectively as powerful as root.
It also required users to be in the input group, which allows any
process to keylog the entire system.
The logind provider defaulted to systemd and in order to use elogind,
-Dlogin-provider=elogind was required. This adds 'auto' as a choice
for the login-provider option and sets it as default. Using 'auto',
the build will check for systemd first and if it's not found, try
to find and use elogind automatically.
