[Mesa-dev] [PATCH 3/3] egl/sl: use kms_swrast with vgem instead of a random GPU

[Emil Velikov]

From: Emil Velikov <emil.velikov at collabora.com>

VGEM and kms_swrast were introduced to work with one another.

All we do is CPU rendering to dumb buffers. There is no reason to carve
out GPU memory, increasing the memory pressure on a device that could
make a better use of it.

For kms_swrast to work properly we require the primary node, as the dumb
buffer ioctls are not exposed via the render node.

Note that this requires libdrm commit 3df8a7f0 ("xf86drm: fallback to
MODALIAS for OF less platform devices")

Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
 src/egl/drivers/dri2/platform_surfaceless.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/egl/drivers/dri2/platform_surfaceless.c b/src/egl/drivers/dri2/platform_surfaceless.c
index e1151e3585c..54c6856c63c 100644
--- a/src/egl/drivers/dri2/platform_surfaceless.c
+++ b/src/egl/drivers/dri2/platform_surfaceless.c
@@ -286,10 +286,11 @@ surfaceless_probe_device(_EGLDisplay *dpy, bool swrast)
    for (i = 0; i < num_devices; ++i) {
       device = devices[i];
 
-      if (!(device->available_nodes & (1 << DRM_NODE_RENDER)))
+      const unsigned node_type = swrast ? DRM_NODE_PRIMARY : DRM_NODE_RENDER;
+      if (!(device->available_nodes & (1 << node_type)))
          continue;
 
-      dri2_dpy->fd = loader_open_device(device->nodes[DRM_NODE_RENDER]);
+      dri2_dpy->fd = loader_open_device(device->nodes[node_type]);
       if (dri2_dpy->fd < 0)
          continue;
 
@@ -300,10 +301,17 @@ surfaceless_probe_device(_EGLDisplay *dpy, bool swrast)
          continue;
       }
 
-      if (swrast)
-         dri2_dpy->driver_name = strdup("kms_swrast");
-      else
-         dri2_dpy->driver_name = loader_get_driver_for_fd(dri2_dpy->fd);
+      dri2_dpy->driver_name = loader_get_driver_for_fd(dri2_dpy->fd);
+      if (swrast) {
+         /* Use kms swrast only with vgem */
+         if (strcmp(dri2_dpy->driver_name, "vgem") != 0) {
+            free(dri2_dpy->driver_name);
+            dri2_dpy->driver_name = NULL;
+         } else {
+            free(dri2_dpy->driver_name);
+            dri2_dpy->driver_name = strdup("kms_swrast");
+         }
+      }
 
       if (dri2_dpy->driver_name && dri2_load_driver_dri3(dpy))
          break;
-- 
2.20.1