weston-drm - the DRM backend for Weston
The DRM backend is the native Weston backend for systems that support the Linux
kernel DRM, kernel mode setting (KMS), and evdev input devices. It is the
recommended backend for desktop PCs, and aims to provide the full Wayland
experience with the "every frame is perfect" concept. It also relies
on the Mesa GBM interface.
With the DRM backend, weston
runs without any underlying windowing
system. The backend uses the Linux KMS API to detect connected monitors.
Monitor hot-plugging is supported. Input devices are found automatically by
. Compositing happens mainly in GL ES 2,
initialized through EGL. It is also possible to take advantage of hardware
cursors and overlays, when they exist and are functional. Full-screen surfaces
will be scanned out directly without compositing, when possible. Hardware
accelerated clients are supported via EGL.
The backend chooses the DRM graphics device first based on seat id. If seat
identifiers are not set, it looks for the graphics device that was used in
boot. If that is not found, it finally chooses the first DRM device returned
. Combining multiple graphics devices are not supported yet.
The DRM backend relies on weston-launch
for managing input device access
and DRM master status, so that weston
can be run without root
privileges. On switching away from the virtual terminal (VT) hosting Weston,
all input devices are closed and the DRM master capability is dropped, so that
other servers, including Xorg(1)
, can run on other VTs. On switching
back to Weston's VT, input devices and DRM master are re-acquired through the
parent process weston-launch
The DRM backend uses the following entries from weston.ini
- The KMS connector name identifying the output, for instance
- Specify the video mode for the output. The argument
mode can be one of the words off to turn the output off,
preferred to use the monitor's preferred video mode, or
current to use the current video mode and avoid a mode switch. It
can also be a resolution as widthxheight, or a
detailed mode line as below.
- mode=dotclock hdisp hsyncstart hsyncend htotal
vdisp vsyncstart vsyncend vtotal hflag vflag
- Use the given detailed mode line as the video mode for this
output. The definition is the same as in xorg.conf(5), and
cvt(1) can generate detailed mode lines.
- Transform for the output, which can be rotated in 90-degree
steps and possibly flipped. Possible values are normal, 90,
180, 270, flipped, flipped-90,
flipped-180, and flipped-270.
When the DRM backend is loaded, weston
will understand the following
additional command line options.
- By default, use the current video mode of all outputs,
instead of switching to the monitor preferred mode.
- Use the DRM device cardN instead of the default
heuristics based on seat assignments and boot VGA status. For example, use
- Use graphics and input devices designated for seat
seatid instead of the default seat seat0.
- Launch Weston on tty x instead of using the current
- The file descriptor (integer) of the opened tty where
weston will run. Set by weston-launch.
- The file descriptor (integer) where weston-launch is
listening. Automatically set by weston-launch.