egl: add support for EGL_EXT_device_drm_render_node

This new EGL extension has been introduced in [1].

When we have a DRM device and a render node, we can advertise the
extension and return the render node name for the
EGL_DRM_RENDER_NODE_FILE_EXT query.

For the special software EGL device, we can advertise the extension
and return NULL for the EGL_DRM_RENDER_NODE_FILE_EXT query, because
we can guarantee that llvmpipe will never use a render node for
rendering operations.

However, llvmpipe might be using a primary node when used with the
GBM platform. So we can't advertise EXT_device_drm in this case.

When we have a DRM device but no render node, that means we're on a
split render/display SoC. We _should_ return the render node used
by the renderonly driver, however Mesa needs more plumbing to allow
this, so let's just disable the extension for now.

[1]: https://github.com/KhronosGroup/EGL-Registry/pull/127

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11797>

src/egl/main/egldevice.c

@@ -45,6 +45,7 @@ struct _egl_device {
 
    EGLBoolean MESA_device_software;
    EGLBoolean EXT_device_drm;
+   EGLBoolean EXT_device_drm_render_node;
 
 #ifdef HAVE_LIBDRM
    drmDevicePtr device;
@@ -97,8 +98,10 @@ _eglCheckDeviceHandle(EGLDeviceEXT device)
 }
 
 _EGLDevice _eglSoftwareDevice = {
-   .extensions = "EGL_MESA_device_software",
+   /* TODO: EGL_EXT_device_drm support for KMS + llvmpipe */
+   .extensions = "EGL_MESA_device_software EGL_EXT_device_drm_render_node",
    .MESA_device_software = EGL_TRUE,
+   .EXT_device_drm_render_node = EGL_TRUE,
 };
 
 #ifdef HAVE_LIBDRM
@@ -143,6 +146,12 @@ _eglAddDRMDevice(drmDevicePtr device, _EGLDevice **out_dev)
    dev->EXT_device_drm = EGL_TRUE;
    dev->device = device;
 
+   /* TODO: EGL_EXT_device_drm_render_node support for kmsro + renderonly */
+   if (device->available_nodes & (1 << DRM_NODE_RENDER)) {
+      dev->extensions = "EGL_EXT_device_drm EGL_EXT_device_drm_render_node";
+      dev->EXT_device_drm_render_node = EGL_TRUE;
+   }
+
    if (out_dev)
       *out_dev = dev;
 
@@ -197,6 +206,8 @@ _eglDeviceSupports(_EGLDevice *dev, _EGLDeviceExtension ext)
       return dev->MESA_device_software;
    case _EGL_DEVICE_DRM:
       return dev->EXT_device_drm;
+   case _EGL_DEVICE_DRM_RENDER_NODE:
+      return dev->EXT_device_drm_render_node;
    default:
       assert(0);
       return EGL_FALSE;
@@ -236,16 +247,31 @@ _eglQueryDeviceStringEXT(_EGLDevice *dev, EGLint name)
    switch (name) {
    case EGL_EXTENSIONS:
       return dev->extensions;
-#ifdef HAVE_LIBDRM
    case EGL_DRM_DEVICE_FILE_EXT:
-      if (_eglDeviceSupports(dev, _EGL_DEVICE_DRM))
+      if (!_eglDeviceSupports(dev, _EGL_DEVICE_DRM))
-         return dev->device->nodes[DRM_NODE_PRIMARY];
+         break;
+#ifdef HAVE_LIBDRM
+      return dev->device->nodes[DRM_NODE_PRIMARY];
+#else
+      /* This should never happen: we don't yet support EGL_DEVICE_DRM for the
+       * software device, and physical devices are only exposed when libdrm is
+       * available. */
+      assert(0);
+      break;
 #endif
-      FALLTHROUGH;
+   case EGL_DRM_RENDER_NODE_FILE_EXT:
-   default:
+      if (!_eglDeviceSupports(dev, _EGL_DEVICE_DRM_RENDER_NODE))
-      _eglError(EGL_BAD_PARAMETER, "eglQueryDeviceStringEXT");
+         break;
+#ifdef HAVE_LIBDRM
+      return dev->device ? dev->device->nodes[DRM_NODE_RENDER] : NULL;
+#else
+      /* Physical devices are only exposed when libdrm is available. */
+      assert(_eglDeviceSupports(dev, _EGL_DEVICE_SOFTWARE));
       return NULL;
-   };
+#endif
+   }
+   _eglError(EGL_BAD_PARAMETER, "eglQueryDeviceStringEXT");
+   return NULL;
 }
 
 /* Do a fresh lookup for devices.

src/egl/main/egldevice.h

@@ -61,6 +61,7 @@ _eglAddDevice(int fd, bool software);
 enum _egl_device_extension {
    _EGL_DEVICE_SOFTWARE,
    _EGL_DEVICE_DRM,
+   _EGL_DEVICE_DRM_RENDER_NODE,
 };
 
 typedef enum _egl_device_extension _EGLDeviceExtension;