drm-shim: Let the driver choose to overwrite the first render node.

When I was writing drm-shim, I was focused on the v3d kmsro case -- use my
intel device as the kmsro display device and add on a simulator-based v3d
device that we could render with.  But for the noop backends we use for
shader-db, it's a lot more useful to just overwrite the first render node
in the system so that you don't have to pass a -d <how many render nodes I
already have in my system> argument.

Reviewed-by: Lionel Landwerlin <[email protected]>
Reviewed-by: Iago Toral Quiroga <[email protected]>
Reviewed-by: Christian Gmeiner <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4664>

1 files changed, 6 insertions, 3 deletions

diff --git a/src/drm-shim/drm_shim.c b/src/drm-shim/drm_shim.c
index 325a8a142e5..61a1cb2ae50 100644
--- a/src/drm-shim/drm_shim.c
+++ b/src/drm-shim/drm_shim.c
@@ -97,9 +97,11 @@ struct file_override {
 };
 static struct file_override file_overrides[10];
 static int file_overrides_count;
+extern bool drm_shim_driver_prefers_first_render_node;
 
-/* Come up with a filename for a render node that doesn't actually exist on
- * the system.
+/* Pick the minor and filename for our shimmed render node.  This can be
+ * either a new one that didn't exist on the system, or if the driver wants,
+ * it can replace the first render node.
  */
 static void
 get_dri_render_node_minor(void)
@@ -110,7 +112,8 @@ get_dri_render_node_minor(void)
       asprintf(&render_node_path, "/dev/dri/%s",
                render_node_dirent_name);
       struct stat st;
-      if (stat(render_node_path, &st) == -1) {
+      if (drm_shim_driver_prefers_first_render_node ||
+          stat(render_node_path, &st) == -1) {
 
          render_node_minor = minor;
          return;