This function is only used for logind, which is Linux-specific, but the
presence in common/drm.c suggested that it had to be portable.
Move it to the logind backend for now.
sd_bus_call_method may have read and queued our ping response, so we
cannot assume that a previous ping will make the socket readable.
Instead, always send a ping if read or write queues are not empty, even
if a ping has already been sent.
This reduces the boilerplate a bit. Use logind.name() instead of
having a separate source of truth. Requires adapting the checks a
bit because the dep name has a "lib" prefix.
sd_bus_call drains received messages into the receive queue, and peeks
for its own return value. It does not dispatch the receive queue.
As the socket is drained, the caller will not wake from a poll and have
no reason to dispatch libseat. This has gone unnoticed largely due to
logind sending an event for every device, making it unlikely that no
unread message will be left on the socket.
Like we have done for seatd, we fix this by sending a "ping" request to
logind if anything is left in our receive queue as reported by
sd_bus_get_events. The response to this will wake us up and ensure that
dispatch is called.
When device open or close messages are sent to seatd, libseat must read
messages from the socket until it sees the associated response message.
This means that it may drain enable/disable seat events from the socket,
queueing them internally for deferred processing.
As the socket is drained, the caller will not wake from a poll and have
no reason to dispatch libseat. To ensure that these messages would not
be left in the queue, 6fa82930d0 made it
so that open/close calls would execute all queued events just before
returning.
Unfortunately, this had the side-effect of having events fire from the
stack of libseat_open_device or libseat_close_device, which we now see
cause problems in compositors. Specifically, an issue has been observed
where libinput end up calling libseat_close_device, which in turn
dispatch a disable seat event that calls libinput_suspend. libinput does
not like this.
Instead, remove the execution from libseat_open_device and
libseat_close_device, and instead make a "ping" request to seatd if
events have been queued. The response to this will wake us up and ensure
that dispatch is called.
This reverts commit 1ae6c3b3dd.
A user might want to run the builtin server as non root, if they have
permission to use the devices.
The check was originally copied from wlroots's direct backend. It was reverted
in fa05d3cde68d with a detailed explanation of why root priviledges are not
always necessary to use the DRM device.
This handler returns the number of dispatched or executed events, or -1
if dispatch_pending failed.
This helper is used to clean up dispatch_background, which now ensures
that all events are executed before we read or poll the connection, and
have improved error handling in the corner case where the second
dispatch_pending failed.
Dispatch needs to report if something has happened, which includes
events executed from the queue as these could have lead to additional
dispatch and queuing.
The socket is expected not to be found if seatd is not running.
In general other backends will be attempted after seatd. There is
already an error message in case no backend can be started.
clang-format wants to put the terminating NULLs on the same line as the
noop backend when it doens't have any immediate non-NULL neighbors.
Add a newline to stop it.
This is useful for headless testing, for instance with VKMS:
modprobe vkms
export WLR_DRM_DEVICES=/dev/dri/card1
export WLR_BACKENDS=drm
export LIBSEAT_BACKEND=noop
sway
We don't need any of the VT handling in this case.
This is not strictly speaking necessary as detaching from the bus should
trigger this automatically, but elogind apparently has issues with this.
Doing this explicitly does no harm, so let's just do that.
The most common pain point I've seen with people trying out seat is
forgetting to add themselves to whatever group the distro has chosen
to own the socket.
Logging this error and path of the socket should make it easier to tell
why things aren't working.
If a background event was queued during call dispatch, and no unread
data was left on the socket, there would be no incentive for the user to
call dispatch, and as a result, the events would never be executed.
Execute events at the end of IPC calls that read from the socket to
avoid stalls.
Dispatch on IPC call only dispatched until the first message was
successfully processed. This could lead to premature dispatch
termination if a background event was received during an IPC call.
Instead, continue dispatching until a non-bg opcode is reported or an
error is received.
Add helpers around connection access to have all logging centralized and
reduce code duplication. Improve existing helpers to further reduce code
duplication.
The seatd backend should have much better logging after this.
