From 27ed515c0519f7907362081c790d98240f0919eb Mon Sep 17 00:00:00 2001
From: Jesse Natalie <jenatali@microsoft.com>
Date: Tue, 8 Dec 2020 16:32:03 -0800
Subject: [PATCH] drisw: Add fallback logic for choosing a driver to use

Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8128>
---
 .../target-helpers/inline_sw_helper.h         | 41 +++++++++++--------
 .../auxiliary/target-helpers/sw_helper.h      | 41 +++++++++++--------
 2 files changed, 50 insertions(+), 32 deletions(-)

diff --git a/src/gallium/auxiliary/target-helpers/inline_sw_helper.h b/src/gallium/auxiliary/target-helpers/inline_sw_helper.h
index e3300940555..9347909f326 100644
--- a/src/gallium/auxiliary/target-helpers/inline_sw_helper.h
+++ b/src/gallium/auxiliary/target-helpers/inline_sw_helper.h
@@ -76,25 +76,34 @@ sw_screen_create_named(struct sw_winsys *winsys, const char *driver)
 static inline struct pipe_screen *
 sw_screen_create(struct sw_winsys *winsys)
 {
-   const char *default_driver;
-   const char *driver;
-
+   const char *drivers[] = {
+      debug_get_option("GALLIUM_DRIVER", ""),
 #if defined(GALLIUM_LLVMPIPE)
-   default_driver = "llvmpipe";
-#elif defined(GALLIUM_SOFTPIPE)
-   default_driver = "softpipe";
-#elif defined(GALLIUM_SWR)
-   default_driver = "swr";
-#elif defined(GALLIUM_ZINK)
-   default_driver = "zink";
-#elif defined(GALLIUM_D3D12)
-   default_driver = "d3d12";
-#else
-   default_driver = "";
+      "llvmpipe",
 #endif
+#if defined(GALLIUM_SOFTPIPE)
+      "softpipe",
+#endif
+#if defined(GALLIUM_SWR)
+      "swr",
+#endif
+#if defined(GALLIUM_ZINK)
+      "zink",
+#endif
+#if defined(GALLIUM_D3D12)
+      "d3d12",
+#endif
+   };
 
-   driver = debug_get_option("GALLIUM_DRIVER", default_driver);
-   return sw_screen_create_named(winsys, driver);
+   for (unsigned i = 0; i < ARRAY_SIZE(drivers); i++) {
+      struct pipe_screen *screen = sw_screen_create_named(winsys, drivers[i]);
+      if (screen)
+         return screen;
+      /* If the env var is set, don't keep trying things */
+      else if (i == 0 && drivers[i][0] != '\0')
+         return NULL;
+   }
+   return NULL;
 }
 
 #endif
diff --git a/src/gallium/auxiliary/target-helpers/sw_helper.h b/src/gallium/auxiliary/target-helpers/sw_helper.h
index fd1ad904dfb..4fbec159d79 100644
--- a/src/gallium/auxiliary/target-helpers/sw_helper.h
+++ b/src/gallium/auxiliary/target-helpers/sw_helper.h
@@ -82,25 +82,34 @@ sw_screen_create_named(struct sw_winsys *winsys, const char *driver)
 struct pipe_screen *
 sw_screen_create(struct sw_winsys *winsys)
 {
-   const char *default_driver;
-   const char *driver;
-
+   const char *drivers[] = {
+      debug_get_option("GALLIUM_DRIVER", ""),
 #if defined(GALLIUM_LLVMPIPE)
-   default_driver = "llvmpipe";
-#elif defined(GALLIUM_SOFTPIPE)
-   default_driver = "softpipe";
-#elif defined(GALLIUM_SWR)
-   default_driver = "swr";
-#elif defined(GALLIUM_ZINK)
-   default_driver = "zink";
-#elif defined(GALLIUM_D3D12)
-   default_driver = "d3d12";
-#else
-   default_driver = "";
+      "llvmpipe",
 #endif
+#if defined(GALLIUM_SOFTPIPE)
+      "softpipe",
+#endif
+#if defined(GALLIUM_SWR)
+      "swr",
+#endif
+#if defined(GALLIUM_ZINK)
+      "zink",
+#endif
+#if defined(GALLIUM_D3D12)
+      "d3d12",
+#endif
+   };
 
-   driver = debug_get_option("GALLIUM_DRIVER", default_driver);
-   return sw_screen_create_named(winsys, driver);
+   for (unsigned i = 0; i < ARRAY_SIZE(drivers); i++) {
+      struct pipe_screen *screen = sw_screen_create_named(winsys, drivers[i]);
+      if (screen)
+         return screen;
+      /* If the env var is set, don't keep trying things */
+      else if (i == 0 && drivers[i][0] != '\0')
+         return NULL;
+   }
+   return NULL;
 }
 
 #endif