[Mesa-dev] [PATCH v2 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.

Note:
 - The original code did not work out of the box, since the dumb buffer
ioctls are not exposed to render nodes.
 - This requires libdrm commit 3df8a7f0 ("xf86drm: fallback to MODALIAS
for OF less platform devices")
 - The non-kms, swrast is unaffected by this change.

v2:
 - elaborate what and how is/isn't working (Eric)
 - simplify driver_name handling (Eric)

Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
---
 src/egl/drivers/dri2/platform_surfaceless.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/egl/drivers/dri2/platform_surfaceless.c b/src/egl/drivers/dri2/platform_surfaceless.c
index ccdc370d059..0917c15e16d 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 *disp, 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 +301,16 @@ surfaceless_probe_device(_EGLDisplay *disp, 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);
+      char *driver_name = loader_get_driver_for_fd(dri2_dpy->fd);
+      if (swrast) {
+         /* Use kms swrast only with vgem */
+         if (strcmp(driver_name, "vgem") == 0)
+            dri2_dpy->driver_name = strdup("kms_swrast");
+         free(driver_name);
+      } else {
+         /* Use the given hardware driver */
+         dri2_dpy->driver_name = driver_name;
+      }
 
       if (dri2_dpy->driver_name && dri2_load_driver_dri3(disp))
          break;
-- 
2.20.1