Add initial version

The initial version implements the basic functionality
of the client/server communication and lease management.

For now, one lease is created per valid connector (dependent
on CRTC availablity).

Bug-AGL: SPEC-3729

Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>
Change-Id: I2b37a892742cc22bdc53a5172c8ad3d8a7bb5e66

1 files changed, 85 insertions, 0 deletions

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+# 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.