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diff --git a/README.md b/README.md new file mode 100644 index 0000000..5368f6b --- /dev/null +++ b/README.md @@ -0,0 +1,85 @@ +# DRM Lease Manager + +The DRM Lease Manager uses the DRM Lease feature, introduced in the Linux kernel version 4.15, +to partition display controller output resources between multiple processes. + +For more information on the DRM lease functionality, please see the blog posts published by Keith +Packard, who developed the feature, at https://keithp.com/blogs/DRM-lease/ + +This repository contains a user space daemon to create and manage DRM leases, and distribute them +to client applications. This implementation is independent of any window system / compositor, +such as X11 or wayland, so can be used with clients that directly access a DRM device. + +This repository also provides a library that clients can use to communicate with the DRM Lease Manager. + +## Building + +Build this repository requires a recent version of the [meson](https://mesonbuild.com/Getting-meson.html) build system. + +The basic build procedure is as follows: + + meson <build_dir> + ninja -C <build_dir> + sudo ninja -C <build_dir> install + +`<build_dir>` can be any directory name, but `build` is commonly used. + +## Running + +Once installed, running the following command will start the DRM Lease Manager daemon + + drm-lease-manager [<path DRM device>] + +If no DRM device is specified, `/dev/dri/card0` will be used. +More detailed options can be displayed by specifying the `-h` flag. + +### Lease naming + +One DRM lease will be created for each connector on the DRM device (up to the number of available CRTCs). + +The names of the DRM leases will have the following pattern: + + <device>-<connector name> + +So, for example, a DRM lease for the first LVDS device on the device `/dev/dri/card0` would be named +`card0-LVDS-1`. + +## Client API usage + +The libdmclient handles all communication with the DRM Lease Manager and provides file descriptors that +can be used as if the DRM device was opened directly. Clients only need to replace their calls to +`drmOpen()` and `drmClose()` with the appropriate libdlmclient API calls. + +The client library API is described in `dlmclient.h` in the `libdlmclient` directory. + +If doxygen is available, building the repository will generate doxygen documentation in the +`<build_dir>/libdlmclient/docs/html` directory. + +### Examples + +_Error handling has been omitted for brevity and clarity of examples._ + +#### Requesting a lease from the DRM Lease Manager + +```c + struct dlm_lease *lease = dlm_get_lease("card0-HDMI-A-1"); + int drm_device_fd = dlm_lease_fd(lease); +``` + +`drm_device_fd` can now be used to access the DRM device + +#### Releasing a lease + +```c + dlm_release_lease(lease); +``` + +**Note: `drm_device_fd` is not usable after calling `dlm_release_lease()`** + +## Runtime directory +A runtime directory under the `/var` system directory is used by the drm-lease-manager and clients to +communicate with each other. +The default path is `/var/run/drm-lease-manager`, but can be changed by setting the `-Druntime_subdir` +option during configuration with `meson`. + +The runtime directory can also be specified at runtime by setting the `DLM_RUNTIME_PATH` environment variable. |