dri: Remove the globalDriverAPI hacks

We now know that we always have access to the appropriate driver
extensions, so we can get the right __DriverAPIRec from the vtable.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15649>

src/gallium/frontends/dri/dri_util.c

@@ -91,23 +91,6 @@ setupLoaderExtensions(__DRIscreen *psp,
     }
 }
 
-/**
- * This pointer determines which driver API we'll use in the case of the
- * loader not passing us an explicit driver extensions list (that would,
- * itself, contain a pointer to a driver API.)
- *
- * A driver's driDriverGetExtensions_drivername() can update this pointer to
- * what it's returning, and a loader that is ignorant of createNewScreen2()
- * will get the correct driver screen created, as long as no other
- * driDriverGetExtensions() happened in between the first one and the
- * createNewScreen().
- *
- * This allows the X Server to not require the significant dri_interface.h
- * updates for doing createNewScreen2(), which would discourage backporting of
- * the X Server patches to support the new loader interface.
- */
-const struct __DriverAPIRec *globalDriverAPI = &driDriverAPI;
-
 /**
  * This is the first entrypoint in the driver called by the DRI driver loader
  * after dlopen()ing it.
@@ -128,18 +111,11 @@ driCreateNewScreen2(int scrn, int fd,
     if (!psp)
 	return NULL;
 
-    /* By default, use the global driDriverAPI symbol (non-megadrivers). */
-    psp->driver = globalDriverAPI;
-
-    /* If the driver exposes its vtable through its extensions list
-     * (megadrivers), use that instead.
-     */
-    if (driver_extensions) {
-       for (int i = 0; driver_extensions[i]; i++) {
-          if (strcmp(driver_extensions[i]->name, __DRI_DRIVER_VTABLE) == 0) {
-             psp->driver =
-                ((__DRIDriverVtableExtension *)driver_extensions[i])->vtable;
-          }
+    assert(driver_extensions);
+    for (int i = 0; driver_extensions[i]; i++) {
+       if (strcmp(driver_extensions[i]->name, __DRI_DRIVER_VTABLE) == 0) {
+          psp->driver =
+             ((__DRIDriverVtableExtension *)driver_extensions[i])->vtable;
        }
     }
 

src/gallium/frontends/dri/dri_util.h

@@ -143,9 +143,6 @@ struct __DriverAPIRec {
                           int w, int h);
 };
 
-extern const struct __DriverAPIRec driDriverAPI;
-extern const struct __DriverAPIRec *globalDriverAPI;
-
 /**
  * Per-screen private driver information.
  */

src/gallium/targets/dri/target.c

@@ -7,7 +7,6 @@
 const __DRIextension **__driDriverGetExtensions_##drivername(void);       \
 PUBLIC const __DRIextension **__driDriverGetExtensions_##drivername(void) \
 {                                                                         \
-   globalDriverAPI = &galliumdrm_driver_api;                              \
    return galliumdrm_driver_extensions;                                   \
 }
 
@@ -17,7 +16,6 @@ const __DRIextension **__driDriverGetExtensions_swrast(void);
 
 PUBLIC const __DRIextension **__driDriverGetExtensions_swrast(void)
 {
-   globalDriverAPI = &galliumsw_driver_api;
    return galliumsw_driver_extensions;
 }
 
@@ -27,7 +25,6 @@ const __DRIextension **__driDriverGetExtensions_kms_swrast(void);
 
 PUBLIC const __DRIextension **__driDriverGetExtensions_kms_swrast(void)
 {
-   globalDriverAPI = &dri_kms_driver_api;
    return dri_kms_driver_extensions;
 }