Merge pull request #248 from vially/bufferdetect

Implement buffer API autodetection

README.rst

@@ -75,7 +75,7 @@ ENV VARIABLES
 +-----------------------+-----------------------------------------------------+
 | ``WLC_DRM_DEVICE``    | Device to use in DRM mode. (card0 default)          |
 +-----------------------+-----------------------------------------------------+
-| ``WLC_USE_EGLDEVICE`` | Set 1 to force EGL streams instead of GBM.          |
+| ``WLC_BUFFER_API``    | Force buffer API to ``GBM`` or ``EGL``.             |
 +-----------------------+-----------------------------------------------------+
 | ``WLC_SHM``           | Set 1 to force EGL clients to use shared memory.    |
 +-----------------------+-----------------------------------------------------+
@@ -110,12 +110,12 @@ The permissions will be dropped runtime.
 BUFFER API
 ----------
 
-``wlc`` supports both ``GBM`` and ``EGL streams`` buffer APIs. ``GBM`` is used by default and is supported by most GPU drivers except the NVIDIA proprietary driver.
+``wlc`` supports both ``GBM`` and ``EGL`` streams buffer APIs. The buffer API is auto-detected based on the driver used by the DRM device.
 
-If you have a NVIDIA GPU using the proprietary driver you need to:
+- ``GBM`` is supported by most GPU drivers except the NVIDIA proprietary driver.
+- ``EGL`` is only supported by the NVIDIA proprietary. If you have a NVIDIA GPU using the proprietary driver you need to enable DRM KMS using the ``nvidia-drm.modeset=1`` kernel parameter.
 
-- enable DRM KMS using the ``nvidia-drm.modeset=1`` kernel parameter
-- enable the ``EGL streams`` support by setting the ``WLC_USE_EGLDEVICE`` environment variable: ``export WLC_USE_EGLDEVICE=1``
+You can force a given buffer API by setting the ``WLC_BUFFER_API`` environment variable to ``GBM`` or ``EGL``.
 
 ISSUES
 ------

src/platform/backend/drm.c

@@ -591,10 +591,26 @@ update_outputs(struct chck_pool *outputs)
    return count;
 }
 
+static bool
+use_egldevice(int drm_fd)
+{
+   const char *buffer_api = getenv("WLC_BUFFER_API");
+   if (chck_cstr_is_empty(buffer_api)) {
+      drmVersion *version;
+      if (!(version = drmGetVersion(drm_fd)))
+         return false;
+
+      bool use_egl = chck_cstreq(version->name, "nvidia-drm");
+      drmFreeVersion(version);
+      return use_egl;
+   }
+
+   return chck_cstreq(buffer_api, "EGL");
+}
+
 bool
 wlc_drm(struct wlc_backend *backend)
 {
-   chck_cstr_to_bool(getenv("WLC_USE_EGLDEVICE"), &drm.use_egldevice);
    drm.fd = -1;
 
    const char *device = getenv("WLC_DRM_DEVICE");
@@ -611,6 +627,8 @@ wlc_drm(struct wlc_backend *backend)
    if (drm.fd < 0)
       goto card_open_fail;
 
+   drm.use_egldevice = use_egldevice(drm.fd);
+
    if (!drm.use_egldevice) {
       /* GBM will load a dri driver, but even though they need symbols from
        * libglapi, in some version of Mesa they are not linked to it. Since