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 udev(7). 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 by udev(7). 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 LVDS1.
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
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.
Use the connector with id number connectorid as the only initial output.
By default, use the current video mode of all outputs, instead of switching to the monitor preferred mode.
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 tty.
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.